Design, Manufacturing, and Testing of 3D-Printed Fittings for Helmet Continuous Positive Airway Pressure Medical Device: A Case Study in Ergonomic Optimisation

Design, Manufacturing, and Testing of 3D-Printed Fittings for Helmet Continuous Positive Airway Pressure Medical Device: A Case Study in Ergonomic Optimisation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Design, Manufacturing, and Testing of 3D-Printed Fittings for Helmet Continuous Positive Airway Pressure Medical Device: A Case Study in Ergonomic Optimisation Paweł Płatek, Natalia Daniel, Kamil Cieplak, Marcin Sarzyński, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6388720/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Nov, 2025 Read the published version in Scientific Reports → Version 1 posted 14 You are reading this latest preprint version Abstract This study presents the geometrical optimisation of fitting connectors to a Continuous Positive Airway Pressure (CPAP) helmet for use with a ventilator in the treatment of acute respiratory failure. The initial design, developed in 2019 during the COVID-19 pandemic, underwent several optimisation stages. The goal was to reduce the size and weight of air supply and exhaust fittings while improving manufacturability via 3D printing. Two additive manufacturing (AM) techniques were evaluated: Fused Filament Fabrication (FFF) and Laser Powder Bed Fusion of polymers (PBF-LB/P). Experimental tests assessed the risk of microplastic particle detachment from components printed with medically approved PET-G and ABS-Medical filaments. ABS-Medical proved the most suitable, demonstrating reduced susceptibility to hairline structure formation during printing. The final optimised geometry, significantly smaller and lighter, was adapted to the selected AM processes. As a result, approximately 150 CPAP helmet fittings were produced and tested in clinical trials. Health sciences/Medical research Physical sciences/Materials science/Biomaterials Physical sciences/Materials science/Materials for devices Health sciences/Health care Health sciences/Health care/Disease prevention Physical sciences/Engineering/Biomedical engineering Physical sciences/Engineering/Mechanical engineering additive manufacturing 3D printing hCPAP ergonomic studies COVID-19 Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 1. Introduction Contemporary Additive Manufacturing (AM) techniques are gaining interest not only in leading branches of industry 1–3 , science 4 but also in bioengineering 5–8 and medicine 9–12 . A broad range of 3D printing techniques and a wide spectrum of available materials with diverse physical and mechanical properties enable the rapid production of objects with complex geometric shapes, often impossible to obtain using standard manufacturing technologies 13 . An additional advantage of 3D printing techniques is the elimination of the need for specialised tools, injection molds, dies, and matrices in low-volume production. These features make 3D printing techniques particularly attractive for the production of components where the key requirement is rapid manufacturing, dynamic responsiveness to emerging market needs, or the resolution of crises resulting from the unavailability of necessary equipment and spare parts. One of the exemplary cases demonstrating the potential of AM techniques was problems related to lack of access to medical equipment during the COVID-19 pandemic, which broke out in 2019 14–20 . In the early stages of the pandemic, due to widespread lockdowns, disrupted logistics chains, and significantly extended delivery times, commonly used 3D printing techniques such as Fused Filament Fabrication (FFF), Selective Laser Sintering (SLS), and Stereolithography (SLA) enabled urgent responses to the most pressing needs 21–24 . By employing these techniques, it was possible to produce personal protective equipment for medical personnel, various diagnostic equipment and tools facilitating patient hospitalisation and treatment 25–30 . Another example indicating the application of 3D printing techniques in supporting the work of medical personnel is the ongoing military conflicts, e.g., in Ukraine or Gaza 6,31,32 . In these situations, 3D printing techniques enable the rapid production of customised parts, and elements of medical equipment that facilitate the work of medical staff in conflict zones, where the delivery of equipment and spare parts can be a prolonged process, sometimes very complicated. The examples of the literature presented 29,33–40 demonstrate that currently available low-cost desktop 3D printers, combined with a wide range of materials approved for biomedical use, provide an attractive alternative for addressing urgent crises in healthcare arising from shortages of medical equipment and supplies. Additionally, these 3D printers allow rapid adaption of the manufactured range of products, modification of their functional features based on needs, and implementation of significant design changes based on the operational requirements of the used equipment. This study aims to present the experiences and results of a project initiative undertaken by a multidisciplinary research team, which, during the COVID-19 pandemic, developed, manufactured and temporarily deployed a custom-designed helmet continuous positive airway pressure (hCPAP) medical device (a helmet with connection fittings) to treat acute respiratory failure resulting from COVID-19 17 . Since the 1990s, hCPAP has been recognised as an effective method for managing acute respiratory failure 41,42 . It operates by delivering via helmet a continuous positive pressure, which is higher than atmospheric pressure, along with a specified oxygen fraction to the airways and lungs during both inspiration and expiration. The primary advantage of hCPAP in the treatment of acute hypoxemic respiratory failure (AHRF) is that it eliminates the need for tracheal intubation, sedation, and mechanical ventilation. In addition, the helmet interface, compared to other types of interfaces, offers effective isolation for infected patients, significantly reducing the risk of contamination and infection transmission. with better toleration for long-term use (2-3 weeks) than face mask for CPAP. In Figure 1, a general view of the preliminary concept for helmet design is shown, along with the inlet (Figure 1.a) and outlet (Figure 1.b) connectors, designed and manufactured using 3D printing technology. The hCPAP helmet depicted in the figure consists of a polyurethane helmet, to which standard threaded sockets (known as Boston valves) were attached via vibration welding. The outlet connector, sealed with an O-ring, integrates a HEPA filter and a PEEP valve to regulate internal helmet pressure. The inlet connector features an internal diffuser to direct airflow and includes a port for oxygen supply. Initial designs were found to be oversized and required refinement to reduce connector dimensions and eliminate threaded connections. This study presents the optimisation of the original connector design, aiming to minimise mass, simplify geometry, remove threaded joints and O-ring seals, and adapt both connectors for 3D printing. While the COVID-19-related equipment shortage has since been resolved, the study offers valuable design guidelines, key engineering solutions, and insights into challenges encountered during the 3D printing of medical fitting components. 2. Materials and Methods Alternative design variants of the hCPAP inlet and outlet connector components were modelled using SolidWorks 2019 CAD software. In addition to standard 3D modelling and 2D drawing tools, the CFD simulation module was used to verify design assumptions for the inlet diffuser and outlet pressure regulation valve. Functional test components were manufactured using the FFF 3D printing method on a Prusa i3 MK3S+ printer (Prusa Research) with medical-grade ABS, PET-G, and TPU-95 filaments. G-codes were generated using Prusa Slicer software. PEEP pressure valve components were produced using the SLS method with a Formiga P110 printer (EOS GmbH, Germany) and medical-grade PA 2200 polyamide. Figure 2 shows the 3D printers used. As part of the study, additional experimental tests were conducted to determine whether high-flow air passing through the inlet connector could cause material particles to erode from the internal walls. A dedicated laboratory set-up was prepared for this purpose, and a Keyence VHX 6000 digital microscope was used to visually assess and estimate the size of the retained plastic particles. The main view of the laboratory setup used is presented in Figure 3. 3. Results 1. Geometrical Optimisation of inlet and outlet connectors Developing an optimal geometric solution for helmet connectors required the elimination of the previously used threaded sockets, which affected the dimensions and weight of the individual components. Based on a literature review, it was determined that the geometry of the connecting elements should comply with the standard specified in EN ISO 5356-1:2015, which precisely defines the shape and dimensions of the connectors used in anaesthesia and respiratory equipment 43 . Taking into account the guidelines regarding the shape and dimensions of connectors and sockets, it was decided that the connector would be joined to the helmet using press-fit fittings. Before starting the design work, an additional test was conducted involving the production of cylindrical samples made of TPU material. These samples were then subjected to an attempt to bond them to the material (transparent TPU approved for skin contact) used for helmet production using vibrational welding. The tested sockets were produced in two variants: the first using the FFF 3D printing technique with PolyFlex TPU-95 material (PolyMaker) and the other one the SLS 3D printing technique with TPU 1301 material (EOS GmbH). Despite positive results regarding the connection quality between the socket made of TPU 1301 material and the helmet material, it was decided that the SLS technique should not be used to produce components of the inlet assembly. Unsintered and loose particles of the feedstock material, in the form of powder (ranging from 22 to 138 µm), could enter the respiratory system of patients undergoing oxygen therapy through the inlet connection, posing a serious health risk. In the case of the FFF technique, no material structures that could detach from the internal walls due to high airflow were observed. Therefore, it was decided that the inlet and outlet socket connectors would ultimately be manufactured from PolyFlex TPU 95 material (Figure 4). According to the EN ISO 5356-1:2015 guidelines, the connectors for the system were designed in the standard "22" size. To streamline the manufacturing process and standardise the components, a unified socket geometry was developed for both the inlet and outlet assemblies of the helmet. Figure 5 provides detailed specifications of the socket shape and dimensions, which are designed to ensure compatibility between the CPAP device and the respirator. By adapting both the inlet and outlet assemblies to the standardised geometry, the system achieves enhanced interoperability and eliminates the need for additional intermediary components. The next stage in completing the design task within the CAD system involved optimising the geometry of the inlet and outlet connectors. Design work was carried out using SolidWorks 2019 software. A key aspect of this process involved CFD simulation studies aimed at enhancing the diffuser's efficiency and reducing its overall dimensions, as proposed in the preliminary solution illustrated in Figure 1.b. The original concept, described in 17 , had not been optimised to achieve minimal size and weight. a) – technical draw, b) – 3D printed socket via FFF technique with the use of PolyFlex TPU 95 material During oxygen therapy, the diffuser serves two critical functions: improving patient comfort by mitigating the direct impact of strong airflow on the face and enhancing air circulation to reduce carbon dioxide accumulation within the helmet. Preliminary CFD analyses of the initial diffuser concept revealed that the proposed solution was suboptimal. Airflow was excessively dispersed against the helmet walls, potentially impeding effective removal of carbon dioxide. Furthermore, the initial one-way valve design required modifications to eliminate the spring and reduce the weight. Based on state-of-the-art results, it was decided that the redesigned diffuser would incorporate a silicone umbrella valve fabricated from medical grade material. The high flexibility of silicone ensures effective prevention of reverse airflow during patient exhalation. This updated solution aligns with the objectives of reducing both weight and complexity while maintaining high functional reliability. Figure 6 illustrates a general view of the preliminary and modified design concepts of the diffuser, which meet the design and technological requirements. The component comprises three parts, with geometry tailored to the specific demands of the FFF 3D printing process. As an optional feature, provision has been made for the installation of an additional umbrella valve. The shapes of individual components were designed to eliminate the need for support material during the 3D printing process. The assembly of diffuser parts is facilitated through snap-fit connections, ensuring simplicity and reliability. A ring-shaped element inside the cover has been incorporated to direct airflow towards the patient’s face, improving therapeutic efficiency. The geometry of the mounting fitting has been designed to align with the dimensions of flexible connectors, proposed to be manufactured using TPU-95 material via 3D printing. The diffuser’s compact size and rounded edges prevent discomfort to patients and interference with medical staff during helmet application or removal. Its design minimizes the risk of damaging either the diffuser or the polyurethane helmet. CFD simulations, conducted using the CAE module in SolidWorks 2019, evaluated performance changes from geometric modifications at airflow rates of 20 l/min and 60 l/min—common in clinical settings. Two configurations were tested: with and without an umbrella valve. Without the valve, airflow is directed by a circular profile on the inner diffuser cover, crucial for guiding the stream. With the valve, this guiding role is reduced. The ring-shaped element on the diffuser cover significantly influences the volume of forward-directed airflow, essential for maintaining air circulation within the helmet, ensuring both functionality and patient comfort. Figure 7 illustrates the airflow distribution generated by the diffuser in the configuration with the umbrella valve at flow rates of 20 l/min and 60 l/min. Figure 8, in contrast, presents the airflow distribution for the configuration without the umbrella valve at the same flow rates. These visualisations emphasise the differences in airflow patterns and provide valuable insight into the diffuser’s performance under varying operating conditions. The next stage of the project involved modifying the geometry of the 3D CAD models of components that are part of the helmet's inlet and outlet system. A detailed characterisation of the air delivery subsystem for the helmet is presented in Figure 9. It consists of a flexible T 22F-type socket (2), an inlet connector with oxygen port (3) and cap (4), and a diffuser (1). For the manufacturing of the components shown in Figure 9, the use of the FFF 3D printing technique was proposed. The next design stage focused on optimising the outlet connector geometry, initially shown in Figure 1b. The final form (Figure 10) was developed to adapt the PEEP valve body to the EN ISO 5356-1:2004 standard, enabling the use of standard HEPA filters. Technological tests were then conducted to assess the feasibility of producing PEEP valves using additive manufacturing techniques - FFF and SLS. Based on test outcomes, optimal process parameters were established, allowing the successful fabrication of the final valve version using both SLS and FFF methods. The PEEP valve is a key component that enables the discharge of exhaled carbon dioxide from the helmet while maintaining adjustable air pressure levels during oxygen therapy, depending on the patient’s condition. It regulates pressure within the helmet in the range of 5–20 cm H₂O. Preliminary design and manufacturing tests using additive manufacturing techniques (FFF and SLS) confirmed the feasibility of 3D printing for valve production. Initial designs featured a spring-supported piston, with springs made of stainless steel or 3D-printed polymer. However, polymer springs showed inconsistent performance under variable temperature and humidity conditions. Additionally, the use of a large thread pitch led to excessive spring tension with minimal angular rotation of the valve cap, limiting pressure regulation. Tests also revealed a need to rescale the valve cap in the 0XY plane to ensure smooth rotation. Based on these findings, several objectives were established for an optimal design: • Application of a stainless steel spring-supported piston; • Using a fine-pitch thread to provide a wide range of pressure regulation; • Minimizing the number of components; • Designing valve body and cap geometry to avoid post-processing and the use of support structures during 3D printing; • Reducing production time per valve. These requirements were fully implemented in the final PEEP valve design, developed using CAD tools. The resulting geometry meets all technical and manufacturing constraints. A general view of the valve is shown in Figure 11. It consists of four parts: (1) the body, (2) the piston, (3) the spring, and (4) the cap nut. To ensure proper connection of the valve to the HEPA filter, the valve body fitting part was designed following the guidelines specified in the EN ISO 5356-1:2004 standard. To achieve an appropriate range of spring tension adjustment for the piston, an M24x2mm thread with a 2.5 mm pitch was used. Both the side surface of the valve body and the front surface of the cap feature markings indicating the recommended airflow rate. An additional flat cutout was proposed on the side surface of the valve body, allowing the application of a pressure scale. The valve calibration was performed based on the experimental tests. Additionally, four rectangular outlet openings were designed on the side surface of the valve body, allowing free airflow from the valve. 2. Risk assessment of particle detachment in 3D-printed components The helmet’s inlet and outlet connectors were redesigned for 3D printing, using two methods: FFF and SLS. Due to the fine polymer powder (50–70 μm) used in SLS, and the associated risk of unmelted particles detaching into the helmet chamber, the inlet connector components (Figure 10) were assigned to the FFF method. Previous studies confirmed FFF poses no health risk to patients. For production, TPU 95 PolyFlex (PolyMaker, China) was chosen for T 22F-type sockets. ABS Medical and PET-G FX 120 (both from Spectrum Filaments, Poland) were selected for diffuser parts and the inlet connector with a drain. TPU-95 supports vibration welding with the helmet, has a Shore hardness of 95A, high elasticity allowing over threefold elongation, and tensile strength of 29 ± 2.8 MPa. These properties enable a secure press-fit with the breathing tube used in respiratory therapy. Meanwhile, ABS Medical is characterised by biocompatibility in accordance with USP Class VI and ISO 10993-1 standards, allowing up to 30 days of contact with the human body, as well as compliance with EU Regulation No. 10/2011 and FDA 21 CFR regarding food contact. The material ensures high print quality, enabling the rapid production of durable components with strong interlayer adhesion. It exhibits thermal resistance with a Vicat softening temperature of 97 ° C and excellent mechanical properties, including a tensile strength of 47 MPa and elongation at break of 16%. It is ideal for producing customised prosthetics and structures supporting rehabilitation [1] . PET-G FX 120 is specifically designed for medical applications and offers high durability and strength. A key feature of this filament is its temperature resistance to 120°C, allowing finished elements to undergo high-temperature steam sterilisation. This makes it suitable for the manufacture of components related to prosthetics, orthoses, and other medical devices [2] . Before fabricating the inlet and outlet connectors, additional tests were conducted to evaluate the erosive effects of high airflow (70 l/min) on 3D-printed elements made from ABS Medical and PET-G. The aim was to assess whether these components could pose a health risk to hospitalized patients by shedding material particles into the helmet’s interior. Due to the potential for unmelted powder detachment, fittings produced using the SLS method—suitable only for external parts of the air supply system—were excluded from the study. The tests focused on FFF-printed PET-G and ABS Medical components. Samples were cylindrical tubes with an internal diameter of 5.6 mm (matching respiratory tube dimensions) and a length of 100 mm. PET-G tubes were printed using a single parameter set, while ABS Medical samples were produced using two different settings – one with the nozzle cooling option enabled and the other without it. The goal was to determine which material generated fewer microplastic particles due to erosive wear from airflow (Figure 12). The samples were visually examined using a Keyence VHX-6000 digital microscope (KEYENCE Corporation, Osaka, Japan). The tubes were positioned to allow internal surface illumination and observation. As shown in Figure 13, PET-G samples displayed persistent, irregular, hair-like structures, even after adjusting printing parameters. A similar issue was observed in ABS Medical samples produced with the default (cooling-enabled) settings. However, disabling the cooling option during ABS printing eliminated these structures, making this configuration the most favorable in terms of minimizing microplastic formation under high-flow conditions. The next stage of verification of the potential detachment of plastic particles involved assessing the presence of microplastics in the housing with a HEPA filter used for testing. The material retained within the housing was placed on a laboratory glass slide, allowing the evaluation of the number and size of particles using a Keyence 6000 VHX (KEYENCE Corporation, Osaka, Japan). Figure 14 illustrates images of the plastic particles captured by the filter. Furthermore, in Table 1, detailed measurements results are presented. Based on the assessment of their size, it was determined that the components of the inlet connector and diffuser would be manufactured using ABS Medical filament, with cooling disabled during the 3D printing process. In the case of tests conducted using samples made of ABS Medical material, no presence of microplastics was found in the HEPA filter housing. Table 1. Results of the observations of microplastics retained in the filter housing after tests Sample number Number of microplastic elements Minimal size [µm] Maximum size [µm] PET-G No.1 24 57x93 535x194 PET-G No.2 20 41x41 358x437 PET-G No.3 10 51x57 207x181 3. Manufacturing process of modified variants of inlet and outlet connectors using 3D printing techniques The initial phase of the task involved the fabrication of T 22F connector sockets, facilitating the production of a batch of 150 helmets required for the start of clinical trials. These trials aim to assess the efficacy of the proposed solution in the treatment of respiratory failure with the use of an hCPAP system. The T 22F socket components were manufactured using the FFF 3D printing technique with PolyFlex TPU-95, a highly flexible material. This material selection enables effective integration of the fabricated fittings with the transparent helmet shell through vibration welding. Figure 15 illustrates an overview of Prusa Slicer software, which was used to generate the G-code program for Prusa i3 MK3S+ 3D printers. Furthermore, Table 2 presents the applied 3D printing parameters used to fabricate the T 22F socket, Table 3 contains information regarding the mechanical and physical properties of the TPU-95 PolyFlex filament. Table 2. 3D printing parameters used for TPU-95 filaments Parameter Minimal value Maximum value Identified value Layer thickness [mm] 0.2 0.4 0.2 Extrusion width [mm] 0.4 0.5 0.4 Nozzle temperature [°C] 210 230 210 Bed temperature [°C] 25 60 50 Cooling option [%] 0 100 0 3D printing speed [mm/s] 30 50 30 Retraction length [mm] 1 3 1 Retraction speed [mm/s] 35 60 35 Table 3. Mechanical Properties of TPU 95 Polyflex filament used in the FFF 3D Printing Technique Parameter Value Young’s Modulus [MPa] 9.4 ± 0.3 Tensile Strength [MPa] 29.0 ± 2.8 Elongation at break [%] 330.1 ± 14.9 Shore hardness 95 A Melting Temperature [°C] 210 Density [kg/m³] 1200 In a single manufacturing cycle, four connector sockets were produced simultaneously. To achieve the target batch size, six identical 3D printers with the same configuration were used. This setup allowed the production of 24 sockets in a four-hour period. Following fabrication, each connector underwent a thorough surface quality inspection. If defects were detected, such as hairline structures, the affected sockets were subjected to additional mechanical post-processing to eliminate these imperfections. Figure 16 provides an overview of the 360 manufactured sockets, which allowed the production of 150 helmets and facilitated additional technological assessments. These additional tests were conducted to optimise the parameters for joining the components using vibration welding, ensuring effective integration with the helmet material. Another component proposed for fabrication using the FFF 3D printing technique was the inlet connector, designed in a variant featuring an additional port to accommodate the connection of an oxygen supply drain (a flexible polyurethane tube with a small cross section). A general view of the characterised connector is presented in the drawings as well as in Fig. 9b. This component was manufactured using ABS Medical material. The choice of material was justified by the results of studies that evaluated the risk of material particle detachment from the inner walls of the components. Fig. 17 illustrates a screenshot of the Prusa Slicer software window with four connectors placed on the build platform. Furthermore, Table 4 presents the 3D printing parameters adopted during the manufacturing process, which were determined based on previous technological tests. Table 5 presents the mechanical properties of the ABS Medical filament. Table 4. 3D printing parameters used in the case of ABS Medical filaments Parameter Minimal value Maximum value Identified value Layer thickness [mm] 0.2 0.4 0.2 Extrusion width [mm] 0.4 0.5 0.45 Nozzle temperature [°C] 235 255 240 Bed temperature [°C] 100 100 100 Cooling option [%] 0 25 25 3D printing speed [mm/s] 30 150 40 Retraction length [mm] 0.5 2 0.8 Retraction speed [mm/s] 25 45 40 Table 5. Mechanical Properties of ABS Medical filament used in FFF 3D Printing Technique Parameter Value Young’s Modulus [MPa] 2450 Yield stress [MPa] 47 Elongation at break [%] 16 Ball indentation hardness [N/mm 2 ] 120 Vicat softening temperature [°C] 97 Density [kg/m³] 1060 The proposed geometry of the inlet connector was designed to allow its production using the 3D printing technique without the need for additional support structures. This optimisation helped to reduce the manufacturing time. During a single technological process, four components were produced simultaneously. As in the previous case, six Prusa i3 MK3S+ 3D printers were used simultaneously for production. The approximate duration of the manufacturing process was 4 hours. Figure 18 presents a general view of the manufactured inlet connectors along with additional sealing plugs designed to fit the oxygen supply drain. The plugs were made of TPU-95 material to ensure the required level of sealing. A total of 150 connectors were produced. The next stage of the production process involved manufacturing diffuser components, which were installed inside the helmet using a press-fit connection. As the diffuser is a critical component of the inlet system, it was decided to fabricate it using FFF 3D printing technology, using ABS Medical filament as the material. A general view of the individual components of the diffuser is presented in Figure 19. The diffuser consists of a main body, an additional ring, and a cover. The proposed geometry and its division into three separate parts significantly optimised the manufacturing process. This modular design enabled the production of each component without the need for additional support structures, enhancing manufacturing efficiency and material use. Figure 20. presents a main view of the manufactured components. To enhance functionality by integrating a directional valve mechanism, a parasol valve can be installed within the diffuser body. This addition prevents the reverse flow of air from the helmet to the power supply unit, ensuring proper airflow control. The production time for a single diffuser was approximately one hour. Each manufacturing cycle produced three diffuser components simultaneously. Since six 3D printers were operated in parallel, a total of 18 diffusers could be fabricated in three hours, significantly improving production efficiency. After the surface quality of the manufactured components was verified, the diffusers were assembled in their final configuration. The next stage in the production of a prototype batch of CPAP helmet components involved the manufacturing of PEEP valves. These valves were fabricated using SLS with polyamide powder PA 2200. Since the PEEP valves are located at the end of the air exhaust system, there is no risk of unmolten powder particles entering the helmet interior. Consequently, the use of SLS as a 3D printing technique is feasible for this application. The manufacturing process was carried out using the 3D printing process parameters listed in Table 6. They were determined based on the results of previously performed additional technological tests to achieve minimal external surface roughness, high geometric quality and high mechanical strength. Furthermore, Table 7 presents the mechanical properties of the polyamide PA 2200 powder. Table 6. 3D printing parameters used in the SLS technique and PA 2200 powder Parameter Identified value Layer thickness [mm] 0.1 Contour speed [mm/s] 3000 Contour Power [W] 13.5 Contour beam offset [mm] 0 Hatching distance [mm] 0.25 Hatching speed [mm/s] 3200 Hatching Power [W] 24 Hatching beam offset [mm/s] 0.12 Table 7. Mechanical Properties of Polyamide PA 2200 powder used in the SLS 3D Printing Technique Parameter Value Young’s Modulus [MPa] 1650 Tensile Strength [MPa] 48 Elongation [%] 18 Melting Temperature [°C] 176 Softening Temperature (1.80 MPa) [°C] 70 Softening Temperature (0.65 MPa) 154 Density [kg/m³] 930 The PEEP valve manufacturing process was based on the model depicted in Figure 11. Figures 21 provide an overview of the components of the PEEP valve produced via the SLS technique. 4. Discussion The proposed modification of the geometric design of the connecting fittings between the CPAP helmet and the ventilator has significantly optimised their construction in terms of overall dimensions, weight, connection method and manufacturing technology. Removal of the Boston sockets, as shown in Figure 1, and their replacement with dedicated T 22F sockets - designed and dimensioned according to the EN ISO 5356-1:2015 standard - have greatly simplified the original design. The new socket variant, manufactured using FFF 3D printing technology with flexible Polyurethane TPU 95, replaces the threaded connection with a press-fit mechanism. This change has led to a reduction in the overall size of the air-oxygen mixture supply and the exhaust components connected to the helmet. Furthermore, eliminating the threaded connection has reduced the number of parts and removed the need for additional seals, which were previously required to minimise the risk of air leakage from the helmet. Figures 22 and 23 present a comparison of the 3D CAD models, highlighting the overall dimensions of the components before and after modification. An additional advantage of the modified geometry of both connector variants was the reduction in their mass. In the case of the inlet connector, the mass was reduced from 85 g to 35.5 g. For the outlet connector, the mass was decreased from 120 g to 34 g. An additional factor contributing to the reduction in the dimensions and mass of the inlet subassembly was the implementation of a redesigned diffuser. Figure 24 presents a comparison of the 3D CAD models of both diffuser variants, along with the corresponding values of their key overall dimensions. This new design features significantly smaller overall dimensions, while also demonstrating enhanced operational efficiency, as validated through computational fluid dynamics (CFD) analysis. Furthermore, the integration of an umbrella valve serves as a critical improvement, enabling one-way flow control. This prevents air from escaping from the helmet into the inlet system and the connected respirator, ensuring optimal performance and safety. The authors’ optimisation of helmet fitting geometry aimed to support additive manufacturing (AM), enabling rapid, tool-free production of fixture sets required for clinical trials. Small-batch fabrication allowed continuous design improvements based on experimental feedback, eliminating early-stage flaws. Iterative adjustments ensured a secure fit between fittings, the helmet, and oxygen therapy devices. Geometric refinement of adjustable components, such as the PEEP valve regulator cap, enabled precise fitting and consistent pressure regulation. Initial production of inlet and outlet connectors used PET-G and ABS Medical with FFF 3D printing. To assess particle detachment risk under high airflow, tests were conducted, confirming that ABS Medical showed superior resistance to material erosion. Due to ABS’s sensitivity to thermal shrinkage, shielding was applied during printing to reduce air circulation and distortion. The redesigned diffuser significantly improved patient comfort. CFD-guided modifications to the housing geometry optimized the internal ring shape, redirecting airflow laterally for better distribution. Symmetrical positioning of ports and mounting sockets in the helmet’s lower section enhanced comfort during prolonged therapy. A one-way medical-grade silicone umbrella valve was integrated into the diffuser, preventing backflow of exhaled air into medical devices, thus increasing system safety and efficiency. As with other fittings, the diffuser was designed within FFF constraints. Components were optimized to eliminate the need for support structures, reducing print time, material waste, and enhancing production efficiency. SLS 3D printing is viable for external PEEP valve parts, where airflow exposure is not a concern. Additional design modifications further streamlined production by enabling direct printing with minimal post-processing. 5. Conclusions The presented case study on optimising the geometry of the inlet and outlet fitting elements of the CPAP helmet exemplifies a structured approach applicable to the design of novel medical equipment. The process was characterised by the integration of advanced computational design tools and state-of-the-art manufacturing techniques, particularly 3D printing. Furthermore, the methodology outlined in this study reflects the iterative nature of contemporary product development, emphasising continuous improvement through successive design refinements. The initial design concept, described in the study introduction, was performed based on an extensive review of the literature, patent analysis, and evaluation of existing market solutions. Taking advantage of this foundational knowledge, the first concept design of the CPAP helmet was developed as a rapid response to the urgent need for respiratory support equipment during the early stages of the COVID-19 pandemic in 2019. Given the shortage of medical devices to treat acute respiratory failure, the proposed solution played a crucial role in addressing this pressing health challenge. Subsequent clinical trials, initially involving volunteers and later expanding to patient participants, provided critical information on the strengths and limitations of the preliminary design. The findings of these trials were fundamental in the next phase of development, which focused on addressing identified shortcomings, optimising the dimensions and weight, and simplifying the manufacturing process to improve overall efficiency and scalability. To summarise, the key modifications implemented by the authors to enhance patient comfort include: 1. The elimination of the proposed Boston connector significantly reduced the size of both the inlet and outlet fittings. Moreover, it considerably simplified the process of attaching the connectors to the helmet. 2. Integration of F-22 sockets, manufactured using advanced 3D printing techniques, designed in compliance with the relevant EN ISO 5356-1:2015 standard, and subsequently bonded to CPAP helmets via vibration welding. This approach ensured a robust and reliable connection while leveraging the benefits of additive manufacturing. 3. Significant reduction in overall dimensions and weight of both inner and outer connectors by replacing the conventional threaded joint with a press-fit connection. This change contributed to improved portability and user comfort while maintaining structural integrity. 4. Optimisation of connector geometry through CAD-based modifications, carefully considering the constraints and capabilities of widely available 3D printing technologies, specifically Fused Filament Fabrication (FFF) and Selective Laser Sintering (SLS). This refinement enhanced manufacturability, ensuring precision and consistency in component production. 5. Additional tests have demonstrated that PET-G, despite its high technological adaptability and suitability for manufacturing components intended for food contact or skin exposure, is not suitable for the production of components used in oxygen therapy. This limitation arises due to the formation of fine, hair-like structures during the 3D printing process, which are challenging to eliminate. 6. In contrast, ABS Medical, although susceptible to thermal shrinkage, exhibits a lower tendency to develop such technological defects. Therefore, the authors recommend its use in the manufacture of medical device components, particularly connectors used in oxygen therapy, such as the CPAP helmet connectors characterised in this study. The design and manufacturing approach presented in this study exemplifies an effective response to crisis scenarios, including pandemics, armed conflicts that lead to supply chain disruptions, and restricted access to essential medical treatments. Declarations Acknowledgments Wroblewski Lukasz reports financial support was provided by Polish Ministry of Science and Higher Education, Centre for Research and Development. The grant NCBR 52/2020. References Ngo, T. D., Kashani, A., Imbalzano, G., Nguyen, K. T. Q. & Hui, D. Additive manufacturing (3D printing): A review of materials, methods, applications and challenges. Compos B Eng 143 , 172–196 (2018). Singh, S., Singh, G., Prakash, C. & Ramakrishna, S. Current status and future directions of fused filament fabrication. J Manuf Process 55 , 288–306 (2020). Wu, W. et al. Deformation mechanism of innovative 3D chiral metamaterials. Sci Rep 8 , (2018). Bai, W. et al. Academic insights and perspectives in 3d printing: A bibliometric review. Applied Sciences (Switzerland) vol. 11 Preprint at https://doi.org/10.3390/app11188298 (2021). Palmara, G., Frascella, F., Roppolo, I., Chiappone, A. & Chiadò, A. Functional 3D printing: Approaches and bioapplications. Biosens Bioelectron 175 , (2021). Mayo, W. et al. Facial defects reconstruction by titanium mesh bending using 3D printing technology: A report of two cases. Annals of Medicine and Surgery 78 , (2022). Guoqing, Z. et al. Design Optimization and Manufacturing of Bio-fixed tibial implants using 3D printing technology. J Mech Behav Biomed Mater 117 , 104415 (2021). Ramlee, M. H. et al. Investigation on three-dimensional printed prosthetics leg sockets coated with different reinforcement materials: analysis on mechanical strength and microstructural. Sci Rep 14 , (2024). Haryńska, A. et al. A comprehensive evaluation of flexible FDM/FFF 3D printing filament as a potential material in medical application. Eur Polym J 138 , 109958 (2020). Palmara, G., Frascella, F., Roppolo, I., Chiappone, A. & Chiadò, A. Functional 3D printing: Approaches and bioapplications. Biosens Bioelectron 175 , (2021). Kabra, A., Mehta, N. & Garg, B. 3D printing in spine care: A review of current applications. J Clin Orthop Trauma 35 , (2022). He, Y., Xue, G. H. & Fu, J. Z. Fabrication of low cost soft tissue prostheses with the desktop 3D printer. Sci Rep 4 , (2014). Zhou, L. et al. Additive Manufacturing: A Comprehensive Review. Sensors vol. 24 Preprint at https://doi.org/10.3390/s24092668 (2024). Vakharia, V. N. et al. Printing in a Pandemic: 3D printing solutions for healthcare during COVID-19. A Protocol for a PRISMA systematic review. Annals of 3D Printed Medicine vol. 2 Preprint at https://doi.org/10.1016/j.stlm.2021.100015 (2021). Manoj, A., Bhuyan, M., Raj Banik, S. & Ravi Sankar, M. 3D printing of nasopharyngeal swabs for COVID-19 diagnose: Past and current trends. in Materials Today: Proceedings vol. 44 1361–1368 (Elsevier Ltd, 2021). Arjunan, A., Zahid, S., Baroutaji, A. & Robinson, J. 3D printed auxetic nasopharyngeal swabs for COVID-19 sample collection. J Mech Behav Biomed Mater 114 , 104175 (2021). Płatek, P. et al. 3D Printing in the Fight Against Covid-19. Medical Devices: Evidence and Research 16 , 167–182 (2023). Wooldridge, A. R., Carman, E. M. & Xie, A. Human Factors and Ergonomics (HFE) applications in responses to the COVID-19 pandemic: Lessons learned and considerations for methods. Appl Ergon 102 , (2022). Nold, J. et al. Air seal performance of personalized and statistically shaped 3D-printed face masks compared with market-available surgical and FFP2 masks. Sci Rep 11 , (2021). Choong, Y. Y. C. et al. The global rise of 3D printing during the COVID-19 pandemic. Nature Reviews Materials vol. 5 637–639 Preprint at https://doi.org/10.1038/s41578-020-00234-3 (2020). Manero, A. et al. Leveraging 3D printing capacity in times of crisis: Recommendations for COVID-19 distributed manufacturing for medical equipment rapid response. Int J Environ Res Public Health 17 , 1–17 (2020). Vordos, N. et al. How 3D printing and social media tackles the PPE shortage during Covid – 19 pandemic. Saf Sci 130 , 104870 (2020). Oladapo, B. I., Ismail, S. O., Afolalu, T. D., Olawade, D. B. & Zahedi, M. Review on 3D printing: Fight against COVID-19. Mater Chem Phys 258 , 123943 (2021). Armani, A. M., Hurt, D. E., Hwang, D., McCarthy, M. C. & Scholtz, A. Low-tech solutions for the COVID-19 supply chain crisis. Nature Reviews Materials vol. 5 403–406 Preprint at https://doi.org/10.1038/s41578-020-0205-1 (2020). Salmi, M. et al. 3D printing in COVID-19: Productivity estimation of the most promising open source solutions in emergency situations. Applied Sciences (Switzerland) 10 , 1–15 (2020). Jafferson, JM. & Pattanashetti, S. Use of 3D printing in production of personal protective equipment (PPE) - a review. Mater Today Proc (2021) doi:10.1016/j.matpr.2021.02.072. Manoj, A., Bhuyan, M., Raj Banik, S. & Ravi Sankar, M. 3D printing of nasopharyngeal swabs for COVID-19 diagnose: Past and current trends. Mater Today Proc (2020) doi:10.1016/j.matpr.2020.11.505. Pedraja, J. et al. Role of 3D printing in the protection of surgical and critical care professionals in the COVID-19 pandemic. Revista Española de Anestesiología y Reanimación (English Edition) 67 , 417–424 (2020). Jafferson, JM. & Pattanashetti, S. Use of 3D printing in production of personal protective equipment (PPE) - a review. Mater Today Proc (2021) doi:10.1016/j.matpr.2021.02.072. Janson, D. J., Clift, B. C. & Dhokia, V. PPE fit of healthcare workers during the COVID-19 pandemic. Appl Ergon 99 , (2022). Kalyniuk, N. M., Franchuk, V. V., Selskyy, P. R., Humenna, N. V. & Hladii, O. I. Blended form of education as an innovative approach in the training of medical students: The experience of Ukraine. Educacion Medica 25 , (2024). Alzhrani, R. F., Alyahya, M. Y., Algahtani, M. S., Fitaihi, R. A. & Tawfik, E. A. Trend of pharmaceuticals 3D printing in the Middle East and North Africa (MENA) region: An overview, regulatory perspective and future outlook. Saudi Pharmaceutical Journal 32 , (2024). Pedraja, J. et al. Role of 3D printing in the protection of surgical and critical care professionals in the COVID-19 pandemic. Revista Española de Anestesiología y Reanimación (English Edition) 67 , 417–424 (2020). Salmi, M. et al. 3D printing in COVID-19: Productivity estimation of the most promising open source solutions in emergency situations. Applied Sciences (Switzerland) 10 , 1–15 (2020). Tareq, M. S., Rahman, T., Hossain, M. & Dorrington, P. Additive manufacturing and the COVID-19 challenges: An in-depth study. J Manuf Syst (2021) doi:10.1016/j.jmsy.2020.12.021. Bibiano-Guillen, C. et al. Adapted Diving Mask (ADM) device as respiratory support with oxygen output during COVID-19 pandemic. American Journal of Emergency Medicine 39 , 42–47 (2021). Vordos, N. et al. How 3D printing and social media tackles the PPE shortage during Covid – 19 pandemic. Saf Sci 130 , 104870 (2020). Maracaja, L., Blitz, D., Maracaja, D. L. V. & Walker, C. A. How 3D Printing Can Prevent Spread of COVID-19 Among Healthcare Professionals During Times of Critical Shortage of Protective Personal Equipment. J Cardiothorac Vasc Anesth 34 , 2847–2849 (2020). Ballard, D. H. et al. Quantitative Fit Tested N95 Respirator-Alternatives Generated With CT Imaging and 3D Printing: A Response to Potential Shortages During the COVID-19 Pandemic. Acad Radiol 28 , 158–165 (2021). Singh, S., Prakash, C. & Ramakrishna, S. Three-dimensional printing in the fight against novel virus COVID-19: Technology helping society during an infectious disease pandemic. Technol Soc 62 , 101305 (2020). Amirfarzan, H. et al. Use of Helmet CPAP in COVID-19 – A practical review. Pulmonology (2021) doi:10.1016/j.pulmoe.2021.01.008. Aliberti, S. et al. Helmet CPAP treatment in patients with COVID-19 pneumonia: a multicentre cohort study. Eur Respir J 56 , (2020). Anaesthetic and respiratory equipment — Conical connectors — Part 1: Cones and sockets. ISO 5356-1:2015(E) 2015 , (2015). Footnotes [1] https://sklep.spectrumfilaments.com/product-pol-1257-Filament-Spectrum-ABS-Medical-1-75mm-1kg.html [2] https://sklep.spectrumfilaments.com/product-pol-1259-Filament-Spectrum-PET-G-FX120-1-75mm-NATURAL-1kg.html Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 25 Nov, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 03 Jun, 2025 Reviews received at journal 30 May, 2025 Reviews received at journal 21 May, 2025 Reviews received at journal 09 May, 2025 Reviews received at journal 09 May, 2025 Reviewers agreed at journal 06 May, 2025 Reviewers agreed at journal 06 May, 2025 Reviewers agreed at journal 04 May, 2025 Reviewers agreed at journal 03 May, 2025 Reviewers agreed at journal 02 May, 2025 Reviewers invited by journal 01 May, 2025 Editor assigned by journal 23 Apr, 2025 Submission checks completed at journal 18 Apr, 2025 First submitted to journal 18 Apr, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6388720","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":451704811,"identity":"e217a161-49ef-4f86-8547-c4b01451a717","order_by":0,"name":"Paweł Płatek","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCUlEQVRIie3QMUvDQBjG8ecIJMsLWV9B2q+QELANqJ8lIZCpmQQRBCsUMunezc/gcnYsHJxLwLVDh4LQSTHSpVMxwUBBSOwoeH+4O+7gR3IHmEx/tRVwXC0Wyu+9V41hN4kAgg1LTAFuCB9GLDqEDJzCX0VYkvswUcFZfn4DZyJZzNpJeDcKvAhrYm0nSZYnDNKXLIp24s0zyREUQVOgMmkxeHTCIu8gL+9P25r0tbtRoRwz+m+/kEUmURNPk5UIqaqvUDcJpx8bjrw1+ToN/Pvd81FO6cUw7rjLwE3jsrxa9npKvfK2uHZdRz0uPmen7T/WPML+xK6n+LZVNATzH8eig5hMJtO/6wvPeEyzO6D3DAAAAABJRU5ErkJggg==","orcid":"","institution":"Military University of Technology, Armament \u0026 Aerospace","correspondingAuthor":true,"prefix":"","firstName":"Paweł","middleName":"","lastName":"Płatek","suffix":""},{"id":451704812,"identity":"16c96312-630e-496a-a62c-0cf641c3fdc3","order_by":1,"name":"Natalia Daniel","email":"","orcid":"","institution":"Military University of Technology, Armament \u0026 Aerospace","correspondingAuthor":false,"prefix":"","firstName":"Natalia","middleName":"","lastName":"Daniel","suffix":""},{"id":451704813,"identity":"8397765a-40a1-4861-b049-ae69b176e81f","order_by":2,"name":"Kamil Cieplak","email":"","orcid":"","institution":"Military University of Technology, Armament \u0026 Aerospace","correspondingAuthor":false,"prefix":"","firstName":"Kamil","middleName":"","lastName":"Cieplak","suffix":""},{"id":451704814,"identity":"a674ff62-e07e-4a9b-855a-f36f19d54e81","order_by":3,"name":"Marcin Sarzyński","email":"","orcid":"","institution":"Military University of Technology, Armament \u0026 Aerospace","correspondingAuthor":false,"prefix":"","firstName":"Marcin","middleName":"","lastName":"Sarzyński","suffix":""},{"id":451704815,"identity":"1de15f11-852f-43dc-ae05-41b70cd4a224","order_by":4,"name":"Janusz Kluczyński","email":"","orcid":"","institution":"Military University of Technology, Faculty of Mechanical Engineering","correspondingAuthor":false,"prefix":"","firstName":"Janusz","middleName":"","lastName":"Kluczyński","suffix":""},{"id":451704816,"identity":"bc379133-0425-458a-b59a-5e0a7dd1d79d","order_by":5,"name":"Grzelak Krzysztof","email":"","orcid":"","institution":"Military University of Technology, Faculty of Mechanical Engineering","correspondingAuthor":false,"prefix":"","firstName":"Grzelak","middleName":"","lastName":"Krzysztof","suffix":""},{"id":451704817,"identity":"56d87aff-1798-4711-9936-87af9d2d0e0f","order_by":6,"name":"Łukasz Wróblewski","email":"","orcid":"","institution":"Medical University of Warsaw, Central Teaching Hospital","correspondingAuthor":false,"prefix":"","firstName":"Łukasz","middleName":"","lastName":"Wróblewski","suffix":""}],"badges":[],"createdAt":"2025-04-06 21:53:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6388720/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6388720/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-25851-2","type":"published","date":"2025-11-25T15:57:50+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82710945,"identity":"2b8d7089-2e5f-4883-85c6-5baebadf7142","added_by":"auto","created_at":"2025-05-14 11:30:41","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":361307,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the preliminary concept of the hCPAP helmet designed and manufactured as a project initiative in the fight against COVID-19 a) outlet connector, b) – inlet connector\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/93ae0eb1e666681723fc31b1.png"},{"id":82710950,"identity":"7a1b234a-9434-47c8-8d4c-2de45ce4e536","added_by":"auto","created_at":"2025-05-14 11:30:41","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":758908,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the 3D printers used to fabricate connector elements a) – Prusa i3 MK3S FFF 3D printer, \u003cbr\u003e\nb) – Formiga P110 SLS 3D printer\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/9ffe33a1cb91913e89ddb89f.png"},{"id":82710951,"identity":"a25e39b3-8f00-41f6-acfc-68ab7b435fdd","added_by":"auto","created_at":"2025-05-14 11:30:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":535503,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the laboratory stand applied to control the potential erosion of 3D printed material subjected to high airflow (a) – set-up used to perform tests, (b) digital microscope to analyse gathered material particles\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/45ef61cb55442e5cd42f0057.png"},{"id":82710952,"identity":"f936287a-ef78-43a8-a294-ab2ad593ad44","added_by":"auto","created_at":"2025-05-14 11:30:41","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":34786,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the modified version of the hCPAP design concept.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/8a8dc1b57551c1c253bf9d32.jpg"},{"id":82710947,"identity":"3051243f-c73d-498e-99ab-95b63cc68d63","added_by":"auto","created_at":"2025-05-14 11:30:41","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the helmet socket designed according to the requirements defined in EN ISO 5356-1:2015 (size ‘22’) \u003cbr\u003e\na) – technical draw, b) – 3D printed socket via FFF technique with the use of PolyFlex TPU 95 material\u003c/p\u003e","description":"","filename":"placeholderImage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/2582545309d313fd363abc20.png"},{"id":82712211,"identity":"87981327-ac97-4c6a-ade7-150ffa275451","added_by":"auto","created_at":"2025-05-14 11:38:41","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the diffuser geometry before and after optimisation process a) – preliminary shape and main dimensions, b) - geometry after CFD studies\u003c/p\u003e","description":"","filename":"placeholderImage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/9c934379ddd9869f5c5cde4d.png"},{"id":82710957,"identity":"bbbb0b33-0807-4188-861f-42b32a657e3b","added_by":"auto","created_at":"2025-05-14 11:30:41","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":12625518,"visible":true,"origin":"","legend":"\u003cp\u003eVisualisation of CFD studies illustrating the airflow direction from the diffuser with umbrella valve: \u003cbr\u003e\n(a) flow rate 20 l/min, (b) - flow rate 60 l/min\u003c/p\u003e","description":"","filename":"Figure7.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/0005bf0e3c8f17fc0d1f34d6.png"},{"id":82712943,"identity":"8f011b95-b3cd-4292-a78b-e473bb02e561","added_by":"auto","created_at":"2025-05-14 11:46:41","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":11747442,"visible":true,"origin":"","legend":"\u003cp\u003eVisualisation of CFD studies illustrating the airflow direction from the diffuser without valve: (a) - flow rate 20 l/min, (b) flow rate 60 l/min\u003c/p\u003e","description":"","filename":"Figure8.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/0ecc761eb801e50541cf3ff6.png"},{"id":82712217,"identity":"665994e3-0204-4048-82b9-fb3badb795aa","added_by":"auto","created_at":"2025-05-14 11:38:41","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":6050698,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the 3D CAD model: a) mounted with global dimensions, b) – exploded view of components 1 – diffuser, 2) – flexible socket of type T 22F-type socket, 3) – connector with additional oxygen port, 4) – cap.\u003c/p\u003e","description":"","filename":"Figure9.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/b5381e7076497afbe44a09ea.png"},{"id":82710974,"identity":"096001f4-284c-4cac-a099-014d319ea231","added_by":"auto","created_at":"2025-05-14 11:30:42","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":5614945,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the 3D CAD model: 1) – flexible T 22F-type socket, 2) – HEPA filter 3) – PEEP valve.\u003c/p\u003e","description":"","filename":"Figure10.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/4039bdfb3446b1ce3e884b64.png"},{"id":82710960,"identity":"83f7b3c4-972e-49b8-a82a-3c82bfbef4bf","added_by":"auto","created_at":"2025-05-14 11:30:41","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":7766597,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of the PEEP Positive End-Expiratory Pressure CAD model: (a) – front view, (b) – exploded view, (c) cross-section view 1) – body, 2) – piston 3) – spring, 4) – cap nut.\u003c/p\u003e","description":"","filename":"Figure11.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/a49c841daa0efe6837a7ab99.png"},{"id":82710972,"identity":"d60d98d2-da7e-40f3-8c67-5def35f4234f","added_by":"auto","created_at":"2025-05-14 11:30:42","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":5166440,"visible":true,"origin":"","legend":"\u003cp\u003eThe laboratory stand used to evaluate the risk of material particles being removed from the internal walls due to high airflow.\u003c/p\u003e","description":"","filename":"Figure12.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/824449f3fe722ad13234eabc.png"},{"id":82712231,"identity":"31d4bd6e-dbdd-49df-8b58-e1b9b550c20b","added_by":"auto","created_at":"2025-05-14 11:38:42","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":8950315,"visible":true,"origin":"","legend":"\u003cp\u003eRegistered microscope images of tube-shaped specimens made from PET-G and ABS medical filaments\u003c/p\u003e","description":"","filename":"Figure13.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/1003c12783d1d1b1187f3630.png"},{"id":82710969,"identity":"166a327c-5a90-4aff-8541-5083994e59c1","added_by":"auto","created_at":"2025-05-14 11:30:42","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":6446295,"visible":true,"origin":"","legend":"\u003cp\u003eMicroplastic size (the smallest and the largest) determined using the Keyence 6000 VHX digital microscope\u003c/p\u003e","description":"","filename":"Figure14.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/1b1e962cacbe5a779fe2706c.png"},{"id":82710975,"identity":"40faa892-a7eb-4dca-95a4-03965492ebf1","added_by":"auto","created_at":"2025-05-14 11:30:42","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":7201817,"visible":true,"origin":"","legend":"\u003cp\u003eOverview of the Prusa Slicer workspace used for generating the G-code to control the 3D printers: (a) isometric view of the 3D model of the connector socket, (b) layer-by-layer slicing of the geometry within the Prusa Slicer software\u003c/p\u003e","description":"","filename":"Figure15.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/1ae2d5edd1929d5e492073ce.png"},{"id":82712228,"identity":"7966c003-f386-49c4-9c78-6044891835d3","added_by":"auto","created_at":"2025-05-14 11:38:42","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":8191892,"visible":true,"origin":"","legend":"\u003cp\u003eView of the fabricated T22F connector sockets: (a) overview of the 360 manufactured connectors, (b) detailed view of the fabricated connectors\u003c/p\u003e","description":"","filename":"Figure16.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/6878f56fca0589a2915bc2b1.png"},{"id":82712947,"identity":"b9325886-d9cc-4718-8f4c-6183e65f98e1","added_by":"auto","created_at":"2025-05-14 11:46:42","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":5524205,"visible":true,"origin":"","legend":"\u003cp\u003eMain view of the single inlet connector with additional oxygen port: (a) isometric view of the 3D CAD model, (b) model sliced into layers in Prusa Slicer software\u003c/p\u003e","description":"","filename":"Figure17.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/8a563ae614669efdb439792c.png"},{"id":82710976,"identity":"1f011ca3-6fe8-42f4-9fe7-5e3cec56d399","added_by":"auto","created_at":"2025-05-14 11:30:42","extension":"png","order_by":18,"title":"Figure 18","display":"","copyAsset":false,"role":"figure","size":7342297,"visible":true,"origin":"","legend":"\u003cp\u003eMain view of the manufactured single-inlet connection components: (a) – detailed view of the manufactured connections, (b) – view of the produced batch of components.\u003c/p\u003e","description":"","filename":"Figure18.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/ee2e5c6f6ed0f8ef0750ba78.png"},{"id":82710981,"identity":"d51acba6-a0ec-4fc2-b0fd-dfb3e4d31953","added_by":"auto","created_at":"2025-05-14 11:30:42","extension":"png","order_by":19,"title":"Figure 19","display":"","copyAsset":false,"role":"figure","size":8297591,"visible":true,"origin":"","legend":"\u003cp\u003eMain view of the diffuser parts: (a) view of 3D models of the parts, \u0026nbsp;(b) view of the Prusa Slicer software window.\u003c/p\u003e","description":"","filename":"Figure19.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/6e2d15b272f88f9df1b0dc75.png"},{"id":82710982,"identity":"8bc363da-d37d-403a-91a5-d4ee989a0b08","added_by":"auto","created_at":"2025-05-14 11:30:42","extension":"png","order_by":20,"title":"Figure 20","display":"","copyAsset":false,"role":"figure","size":10275015,"visible":true,"origin":"","legend":"\u003cp\u003eMain view of the diffuser component manufactured using FFF technology:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e(a) - view of individual components, (b) – view of the batch of manufactured components\u003c/p\u003e","description":"","filename":"Figure20.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/142c50a2f5a9f199822c6bf4.png"},{"id":82710985,"identity":"63c82a0d-5345-4a85-8f08-c3ac0c6c5a1b","added_by":"auto","created_at":"2025-05-14 11:30:42","extension":"png","order_by":21,"title":"Figure 21","display":"","copyAsset":false,"role":"figure","size":5534171,"visible":true,"origin":"","legend":"\u003cp\u003eMain view of the PEEP valve manufactured using the SLS technique: \u003cbr\u003e\n(a) - view of individual components, (b) – view of assembled elements\u003c/p\u003e","description":"","filename":"Figure21.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/0e84e1b8761554049b39d98b.png"},{"id":82712945,"identity":"7abeecf1-8584-4547-8849-7af46adf426b","added_by":"auto","created_at":"2025-05-14 11:46:42","extension":"png","order_by":22,"title":"Figure 22","display":"","copyAsset":false,"role":"figure","size":6598315,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of modification proposed to reduce the size and mass of the inlet connector assembly: (a) – before, (b) – after\u003c/p\u003e","description":"","filename":"Figure22.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/6516edf7c95db2e3875a5c21.png"},{"id":82712233,"identity":"e989e211-8370-4844-a6ad-923efd4995d3","added_by":"auto","created_at":"2025-05-14 11:38:42","extension":"png","order_by":23,"title":"Figure 23","display":"","copyAsset":false,"role":"figure","size":7737225,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of modification proposed to reduce the size and mass of the outlet connector assembly: (a) before, (b) – after\u003c/p\u003e","description":"","filename":"Figure23.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/4c2489fff29d77b89f74b750.png"},{"id":82712238,"identity":"06b75e04-3325-45be-87ee-997ee632b953","added_by":"auto","created_at":"2025-05-14 11:38:42","extension":"png","order_by":24,"title":"Figure 24","display":"","copyAsset":false,"role":"figure","size":5719923,"visible":true,"origin":"","legend":"\u003cp\u003eThe main view of modification proposed to reduce the size and mass of the diffuser assembly: (a) before, (b) – after\u003c/p\u003e","description":"","filename":"Figure24.png","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/e0ddc127eec7b085bdbb71c3.png"},{"id":97179442,"identity":"60a1edb4-4951-439a-a8c7-59bb8e171062","added_by":"auto","created_at":"2025-12-01 16:15:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":139734089,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6388720/v1/6ea1f13a-ab24-4411-bbad-3ccbfd25c959.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Design, Manufacturing, and Testing of 3D-Printed Fittings for Helmet Continuous Positive Airway Pressure Medical Device: A Case Study in Ergonomic Optimisation","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eContemporary Additive Manufacturing (AM) techniques are gaining interest not only in leading branches of industry \u003csup\u003e1\u0026ndash;3\u003c/sup\u003e, science \u003csup\u003e4\u003c/sup\u003e but also in bioengineering \u003csup\u003e5\u0026ndash;8\u003c/sup\u003e and medicine \u003csup\u003e9\u0026ndash;12\u003c/sup\u003e. A broad range of 3D printing techniques and a wide spectrum of available materials with diverse physical and mechanical properties enable the rapid production of objects with complex geometric shapes, often impossible to obtain using standard manufacturing technologies \u003csup\u003e13\u003c/sup\u003e. An additional advantage of 3D printing techniques is the elimination of the need for specialised tools, injection molds, dies, and matrices in low-volume production. These features make 3D printing techniques particularly attractive for the production of components where the key requirement is rapid manufacturing, dynamic responsiveness to emerging market needs, or the resolution of crises resulting from the unavailability of necessary equipment and spare parts.\u003c/p\u003e\n\u003cp\u003eOne of the exemplary cases demonstrating the potential of AM techniques was problems related to lack of access to medical \u0026nbsp;equipment during the COVID-19 pandemic, which broke out in 2019 \u003csup\u003e14\u0026ndash;20\u003c/sup\u003e. In the early stages of the pandemic, due to widespread lockdowns, disrupted logistics chains, and significantly extended delivery times, commonly used 3D printing techniques such as Fused Filament Fabrication (FFF), Selective Laser Sintering (SLS), and Stereolithography (SLA) enabled urgent responses to the most pressing needs \u003csup\u003e21\u0026ndash;24\u003c/sup\u003e. By employing these techniques, it was possible to produce personal protective equipment for medical personnel, various diagnostic equipment and tools facilitating patient hospitalisation and treatment \u003csup\u003e25\u0026ndash;30\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eAnother example indicating the application of 3D printing techniques in supporting the work of medical personnel is the ongoing military conflicts, e.g., in Ukraine or Gaza \u003csup\u003e6,31,32\u003c/sup\u003e. In these situations, 3D printing techniques enable the rapid production of customised parts, and elements of medical equipment that facilitate the work of medical staff in conflict zones, where the delivery of equipment and spare parts can be a prolonged process, sometimes very complicated.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe examples of the literature presented \u003csup\u003e29,33\u0026ndash;40\u003c/sup\u003e demonstrate that currently available low-cost desktop 3D printers, combined with a wide range of materials approved for biomedical use, provide an attractive alternative for addressing urgent crises in healthcare arising from shortages of medical equipment and supplies. Additionally, these 3D printers allow rapid adaption of the manufactured range of products, modification of their functional features based on needs, and implementation of significant design changes based on the operational requirements of the used equipment.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis study aims to present the experiences and results of a project initiative undertaken by a multidisciplinary research team, which, during the COVID-19 pandemic, developed, manufactured and temporarily deployed a custom-designed helmet continuous positive airway pressure (hCPAP) medical device (a helmet with connection fittings) to treat acute respiratory failure resulting from COVID-19 \u003csup\u003e17\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSince the 1990s, hCPAP has been recognised as an effective method for managing acute respiratory failure \u003csup\u003e41,42\u003c/sup\u003e. It operates by delivering via helmet a continuous positive pressure, which is higher than atmospheric pressure, along with a specified oxygen fraction to the airways and lungs during both inspiration and expiration. The primary advantage of hCPAP in the treatment of acute hypoxemic respiratory failure (AHRF) is that it eliminates the need for tracheal intubation, sedation, and mechanical ventilation. In addition, the helmet interface, compared to other types of interfaces, offers effective isolation for infected patients, significantly reducing the risk of contamination and infection transmission. with better toleration for long-term use (2-3 weeks) than face mask for CPAP.\u003c/p\u003e\n\u003cp\u003eIn Figure 1, a general view of the preliminary concept for helmet design is shown, along with the inlet (Figure 1.a) and outlet (Figure 1.b) connectors, designed and manufactured using 3D printing technology. The hCPAP helmet depicted in the figure consists of a polyurethane helmet, to which standard threaded sockets (known as Boston valves) were attached via vibration welding.\u003c/p\u003e\u003cp\u003eThe outlet connector, sealed with an O-ring, integrates a HEPA filter and a PEEP valve to regulate internal helmet pressure. The inlet connector features an internal diffuser to direct airflow and includes a port for oxygen supply. Initial designs were found to be oversized and required refinement to reduce connector dimensions and eliminate threaded connections.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis study presents the optimisation of the original connector design, aiming to minimise mass, simplify geometry, remove threaded joints and O-ring seals, and adapt both connectors for 3D printing. While the COVID-19-related equipment shortage has since been resolved, the study offers valuable design guidelines, key engineering solutions, and insights into challenges encountered during the 3D printing of medical fitting components.\u003c/p\u003e"},{"header":"2.\tMaterials and Methods","content":"\u003cp\u003eAlternative design variants of the hCPAP inlet and outlet connector components were modelled using SolidWorks 2019 CAD software. In addition to standard 3D modelling and 2D drawing tools, the CFD simulation module was used to verify design assumptions for the inlet diffuser and outlet pressure regulation valve. Functional test components were manufactured using the FFF 3D printing method on a Prusa i3 MK3S+ printer (Prusa Research) with medical-grade ABS, PET-G, and TPU-95 filaments. G-codes were generated using Prusa Slicer software. PEEP pressure valve components were produced using the SLS method with a Formiga P110 printer (EOS GmbH, Germany) and medical-grade PA 2200 polyamide. Figure 2 shows the 3D printers used. As part of the study, additional experimental tests were conducted to determine whether high-flow air passing through the inlet connector could cause material particles to erode from the internal walls.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA dedicated laboratory set-up was prepared for this purpose, and a Keyence VHX 6000 digital microscope was used to visually assess and estimate the size of the retained plastic particles. The main view of the laboratory setup used is presented in Figure 3. \u0026nbsp;\u003c/p\u003e"},{"header":"3.\tResults","content":"\u003cp\u003e\u003cstrong\u003e1.\u0026nbsp; Geometrical Optimisation of inlet and outlet connectors\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDeveloping an optimal geometric solution for helmet connectors required the elimination of the previously used threaded sockets, which affected the dimensions and weight of the individual components. Based on a literature review, it was determined that the geometry of the connecting elements should comply with the standard specified in EN ISO 5356-1:2015, which precisely defines the shape and dimensions of the connectors used in anaesthesia and respiratory equipment \u003csup\u003e43\u003c/sup\u003e. Taking into account the guidelines regarding the shape and dimensions of connectors and sockets, it was decided that the connector would be joined to the helmet using press-fit fittings. Before starting the design work, an additional test was conducted involving the production of cylindrical samples made of TPU material. These samples were then subjected to an attempt to bond them to the material (transparent TPU approved for skin contact) used for helmet production using vibrational welding. The tested sockets were produced in two variants: the first using the FFF 3D printing technique with PolyFlex TPU-95 material (PolyMaker) and the other one the SLS 3D printing technique with TPU 1301 material (EOS GmbH). Despite positive results regarding the connection quality between the socket made of TPU 1301 material and the helmet material, it was decided that the SLS technique should not be used to produce components of the inlet assembly. Unsintered and loose particles of the feedstock material, in the form of powder (ranging from 22 to 138 \u0026micro;m), could enter the respiratory system of patients undergoing oxygen therapy through the inlet connection, posing a serious health risk. In the case of the FFF technique, no material structures that could detach from the internal walls due to high airflow were observed. Therefore, it was decided that the inlet and outlet socket connectors would ultimately be manufactured from PolyFlex TPU 95 material (Figure 4).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccording to the EN ISO 5356-1:2015 guidelines, the connectors for the system were designed in the standard \u0026quot;22\u0026quot; size. To streamline the manufacturing process and standardise the components, a unified socket geometry was developed for both the inlet and outlet assemblies of the helmet. Figure 5 provides detailed specifications of the socket shape and dimensions, which are designed to ensure compatibility between the CPAP device and the respirator. By adapting both the inlet and outlet assemblies to the standardised geometry, the system achieves enhanced interoperability and eliminates the need for additional intermediary components.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe next stage in completing the design task within the CAD system involved optimising the geometry of the inlet and outlet connectors. Design work was carried out using SolidWorks 2019 software. A key aspect of this process involved CFD simulation studies aimed at enhancing the diffuser\u0026apos;s efficiency and reducing its overall dimensions, as proposed in the preliminary solution illustrated in Figure 1.b. The original concept, described in \u003csup\u003e17\u003c/sup\u003e, had not been optimised to achieve minimal size and weight.\u003c/p\u003e\n\u003cp\u003ea) \u0026ndash; technical draw, b) \u0026ndash; 3D printed socket via FFF technique with the use of PolyFlex TPU 95 material\u003c/p\u003e\n\u003cp\u003eDuring oxygen therapy, the diffuser serves two critical functions: improving patient comfort by mitigating the direct impact of strong airflow on the face and enhancing air circulation to reduce carbon dioxide accumulation within the helmet.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePreliminary CFD analyses of the initial diffuser concept revealed that the proposed solution was suboptimal. Airflow was excessively dispersed against the helmet walls, potentially impeding effective removal of carbon dioxide. Furthermore, the initial one-way valve design required modifications to eliminate the spring and reduce the weight.\u003c/p\u003e\n\u003cp\u003eBased on state-of-the-art results, it was decided that the redesigned diffuser would incorporate a silicone umbrella valve fabricated from medical grade material. The high flexibility of silicone ensures effective prevention of reverse airflow during patient exhalation. This updated solution aligns with the objectives of reducing both weight and complexity while maintaining high functional reliability.\u003c/p\u003e\n\u003cp\u003eFigure 6 illustrates a general view of the preliminary and modified design concepts of the diffuser, which meet the design and technological requirements. The component comprises three parts, with geometry tailored to the specific demands of the FFF 3D printing process. As an optional feature, provision has been made for the installation of an additional umbrella valve. The shapes of individual components were designed to eliminate the need for support material during the 3D printing process.\u003c/p\u003e\n\u003cp\u003eThe assembly of diffuser parts is facilitated through snap-fit connections, ensuring simplicity and reliability. A ring-shaped element inside the cover has been incorporated to direct airflow towards the patient\u0026rsquo;s face, improving therapeutic efficiency. The geometry of the mounting fitting has been designed to align with the dimensions of flexible connectors, proposed to be manufactured using TPU-95 material via 3D printing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe diffuser\u0026rsquo;s compact size and rounded edges prevent discomfort to patients and interference with medical staff during helmet application or removal. Its design minimizes the risk of damaging either the diffuser or the polyurethane helmet. CFD simulations, conducted using the CAE module in SolidWorks 2019, evaluated performance changes from geometric modifications at airflow rates of 20 l/min and 60 l/min\u0026mdash;common in clinical settings. Two configurations were tested: with and without an umbrella valve. Without the valve, airflow is directed by a circular profile on the inner diffuser cover, crucial for guiding the stream. With the valve, this guiding role is reduced. The ring-shaped element on the diffuser cover significantly influences the volume of forward-directed airflow, essential for maintaining air circulation within the helmet, ensuring both functionality and patient comfort. Figure 7 illustrates the airflow distribution generated by the diffuser in the configuration with the umbrella valve at flow rates of 20 l/min and 60 l/min. Figure 8, in contrast, presents the airflow distribution for the configuration without the umbrella valve at the same flow rates. These visualisations emphasise the differences in airflow patterns and provide valuable insight into the diffuser\u0026rsquo;s performance under varying operating conditions.\u003c/p\u003e\n\u003cp\u003eThe next stage of the project involved modifying the geometry of the 3D CAD models of components that are part of the helmet\u0026apos;s inlet and outlet system. A detailed characterisation of the air delivery subsystem for the helmet is presented in Figure 9. It consists of a flexible T 22F-type socket (2), an inlet connector with oxygen port (3) and cap (4), and a diffuser (1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor the manufacturing of the components shown in Figure 9, the use of the FFF 3D printing technique was proposed.\u003c/p\u003e\n\u003cp\u003eThe next design stage focused on optimising the outlet connector geometry, initially shown in Figure 1b. The final form (Figure 10) was developed to adapt the PEEP valve body to the EN ISO 5356-1:2004 standard, enabling the use of standard HEPA filters. Technological tests were then conducted to assess the feasibility of producing PEEP valves using additive manufacturing techniques - FFF and SLS. Based on test outcomes, optimal process parameters were established, allowing the successful fabrication of the final valve version using both SLS and FFF methods.\u003c/p\u003e\n\u003cp\u003eThe PEEP valve is a key component that enables the discharge of exhaled carbon dioxide from the helmet while maintaining adjustable air pressure levels during oxygen therapy, depending on the patient\u0026rsquo;s condition. It regulates pressure within the helmet in the range of 5\u0026ndash;20 cm H₂O. Preliminary design and manufacturing tests using additive manufacturing techniques (FFF and SLS) confirmed the feasibility of 3D printing for valve production. Initial designs featured a spring-supported piston, with springs made of stainless steel or 3D-printed polymer. However, polymer springs showed inconsistent performance under variable temperature and humidity conditions. Additionally, the use of a large thread pitch led to excessive spring tension with minimal angular rotation of the valve cap, limiting pressure regulation. Tests also revealed a need to rescale the valve cap in the 0XY plane to ensure smooth rotation.\u003c/p\u003e\n\u003cp\u003eBased on these findings, several objectives were established for an optimal design:\u003c/p\u003e\n\u003cp\u003e\u0026bull; Application of a stainless steel spring-supported piston;\u003c/p\u003e\n\u003cp\u003e\u0026bull; Using a fine-pitch thread to provide a wide range of pressure regulation;\u003c/p\u003e\n\u003cp\u003e\u0026bull; Minimizing the number of components;\u003c/p\u003e\n\u003cp\u003e\u0026bull; Designing valve body and cap geometry to avoid post-processing and the use of support structures during 3D printing;\u003c/p\u003e\n\u003cp\u003e\u0026bull; Reducing production time per valve.\u003c/p\u003e\n\u003cp\u003eThese requirements were fully implemented in the final PEEP valve design, developed using CAD tools. The resulting geometry meets all technical and manufacturing constraints. A general view of the valve is shown in Figure 11. It consists of four parts: (1) the body, (2) the piston, (3) the spring, and (4) the cap nut.\u003c/p\u003e\n\u003cp\u003eTo ensure proper connection of the valve to the HEPA filter, the valve body fitting part was designed following the guidelines specified in the EN ISO 5356-1:2004 standard. To achieve an appropriate range of spring tension adjustment for the piston, an M24x2mm thread with a 2.5 mm pitch was used. Both the side surface of the valve body and the front surface of the cap feature markings indicating the recommended airflow rate. An additional flat cutout was proposed on the side surface of the valve body, allowing the application of a pressure scale. The valve calibration was performed based on the experimental tests. Additionally, four rectangular outlet openings were designed on the side surface of the valve body, allowing free airflow from the valve.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. \u0026nbsp; Risk assessment of particle detachment in 3D-printed components\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe helmet\u0026rsquo;s inlet and outlet connectors were redesigned for 3D printing, using two methods: FFF and SLS. Due to the fine polymer powder (50\u0026ndash;70 \u0026mu;m) used in SLS, and the associated risk of unmelted particles detaching into the helmet chamber, the inlet connector components (Figure 10) were assigned to the FFF method. Previous studies confirmed FFF poses no health risk to patients.\u003c/p\u003e\n\u003cp\u003eFor production, TPU 95 PolyFlex (PolyMaker, China) was chosen for T 22F-type sockets. ABS Medical and PET-G FX 120 (both from Spectrum Filaments, Poland) were selected for diffuser parts and the inlet connector with a drain. TPU-95 supports vibration welding with the helmet, has a Shore hardness of 95A, high elasticity allowing over threefold elongation, and tensile strength of 29 \u0026plusmn; 2.8 MPa. These properties enable a secure press-fit with the breathing tube used in respiratory therapy.\u003c/p\u003e\n\u003cp\u003eMeanwhile, ABS Medical is characterised by biocompatibility in accordance with USP Class VI and ISO 10993-1 standards, allowing up to 30 days of contact with the human body, as well as compliance with EU Regulation No. 10/2011 and FDA 21 CFR regarding food contact. The material ensures high print quality, enabling the rapid production of durable components with strong interlayer adhesion. It exhibits thermal resistance with a Vicat softening temperature of 97 \u0026deg; C and excellent mechanical properties, including a tensile strength of 47 MPa and elongation at break of 16%. It is ideal for producing customised prosthetics and structures supporting rehabilitation\u003csup\u003e[1]\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePET-G FX 120 is specifically designed for medical applications and offers high durability and strength. A key feature of this filament is its temperature resistance to 120\u0026deg;C, allowing finished elements to undergo high-temperature steam sterilisation. This makes it suitable for the manufacture of components related to prosthetics, orthoses, and other medical devices\u003csup\u003e[2]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eBefore fabricating the inlet and outlet connectors, additional tests were conducted to evaluate the erosive effects of high airflow (70 l/min) on 3D-printed elements made from ABS Medical and PET-G. The aim was to assess whether these components could pose a health risk to hospitalized patients by shedding material particles into the helmet\u0026rsquo;s interior. Due to the potential for unmelted powder detachment, fittings produced using the SLS method\u0026mdash;suitable only for external parts of the air supply system\u0026mdash;were excluded from the study.\u003c/p\u003e\n\u003cp\u003eThe tests focused on FFF-printed PET-G and ABS Medical components. Samples were cylindrical tubes with an internal diameter of 5.6 mm (matching respiratory tube dimensions) and a length of 100 mm. PET-G tubes were printed using a single parameter set, while ABS Medical samples were produced using two different settings \u0026ndash; one with the nozzle cooling option enabled and the other without it.\u003c/p\u003e\n\u003cp\u003eThe goal was to determine which material generated fewer microplastic particles due to erosive wear from airflow (Figure 12). The samples were visually examined using a Keyence VHX-6000 digital microscope (KEYENCE Corporation, Osaka, Japan). The tubes were positioned to allow internal surface illumination and observation. As shown in Figure 13, PET-G samples displayed persistent, irregular, hair-like structures, even after adjusting printing parameters. A similar issue was observed in ABS Medical samples produced with the default (cooling-enabled) settings. However, disabling the cooling option during ABS printing eliminated these structures, making this configuration the most favorable in terms of minimizing microplastic formation under high-flow conditions.\u003c/p\u003e\n\u003cp\u003eThe next stage of verification of the potential detachment of plastic particles involved assessing the presence of microplastics in the housing with a HEPA filter used for testing. The material retained within the housing was placed on a laboratory glass slide, allowing the evaluation of the number and size of particles using a Keyence 6000 VHX (KEYENCE Corporation, Osaka, Japan). Figure 14 illustrates images of the plastic particles captured by the filter. Furthermore, in Table 1, detailed measurements results are presented. Based on the assessment of their size, it was determined that the components of the inlet connector and diffuser would be manufactured using ABS Medical filament, with cooling disabled during the 3D printing process. In the case of tests conducted using samples made of ABS Medical material, no presence of microplastics was found in the HEPA filter housing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Results of the observations of microplastics retained in the filter housing after tests\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"529\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSample number\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of\u0026nbsp;\u003cbr\u003e\u0026nbsp;microplastic\u0026nbsp;\u003cbr\u003e\u0026nbsp;elements\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMinimal size\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e[\u0026micro;m]\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMaximum size\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e[\u0026micro;m]\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003ePET-G No.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e57x93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e535x194\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003ePET-G No.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e41x41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e358x437\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003ePET-G No.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e51x57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e207x181\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e3. \u0026nbsp;Manufacturing process of modified variants of inlet and outlet connectors using 3D printing techniques\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe initial phase of the task involved the fabrication of T 22F connector sockets, facilitating the production of a batch of 150 helmets required for the start of clinical trials. These trials aim to assess the efficacy of the proposed solution in the treatment of respiratory failure with the use of an hCPAP system. The T 22F socket components were manufactured using the FFF 3D printing technique with PolyFlex TPU-95, a highly flexible material. This material selection enables effective integration of the fabricated fittings with the transparent helmet shell through vibration welding. Figure 15 illustrates an overview of Prusa Slicer software, which was used to generate the G-code program for Prusa i3 MK3S+ 3D printers. Furthermore, Table 2 presents the applied 3D printing parameters used to fabricate the T 22F socket, Table 3 contains information regarding the mechanical and physical properties of the TPU-95 PolyFlex filament.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2.\u003c/strong\u003e 3D printing parameters used for TPU-95 filaments\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"529\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMinimal value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMaximum value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eIdentified value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eLayer thickness [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eExtrusion width [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eNozzle temperature [\u0026deg;C]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e210\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e230\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e210\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eBed temperature [\u0026deg;C]\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eCooling option [%]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003e3D printing speed [mm/s]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eRetraction length [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eRetraction speed [mm/s]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3.\u0026nbsp;\u003c/strong\u003e Mechanical Properties of TPU 95 Polyflex filament used in the FFF 3D Printing Technique\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"363\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eParameter\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eValue\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eYoung\u0026rsquo;s Modulus [MPa]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e9.4 \u0026plusmn; 0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eTensile Strength [MPa]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e29.0 \u0026plusmn; 2.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eElongation at break [%]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e330.1 \u0026plusmn; 14.9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eShore hardness\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e95 A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eMelting Temperature [\u0026deg;C]\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e210\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eDensity [kg/m\u0026sup3;]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e1200\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eIn a single manufacturing cycle, four connector sockets were produced simultaneously. To achieve the target batch size, six identical 3D printers with the same configuration were used. This setup allowed the production of 24 sockets in a four-hour period. Following fabrication, each connector underwent a thorough surface quality inspection. If defects were detected, such as hairline structures, the affected sockets were subjected to additional mechanical post-processing to eliminate these imperfections. Figure 16 provides an overview of the 360 manufactured sockets, which allowed the production of 150 helmets and facilitated additional technological assessments. These additional tests were conducted to optimise the parameters for joining the components using vibration welding, ensuring effective integration with the helmet material.\u003c/p\u003e\n\u003cp\u003eAnother component proposed for fabrication using the FFF 3D printing technique was the inlet connector, designed in a variant featuring an additional port to accommodate the connection of an oxygen supply drain (a flexible polyurethane tube with a small cross section). A general view of the characterised connector is presented in the drawings as well as in Fig. 9b. This component was manufactured using ABS Medical material. The choice of material was justified by the results of studies that evaluated the risk of material particle detachment from the inner walls of the components. Fig. 17 illustrates a screenshot of the Prusa Slicer software window with four connectors placed on the build platform. Furthermore, Table 4 presents the 3D printing parameters adopted during the manufacturing process, which were determined based on previous technological tests. Table 5 presents the mechanical properties of the ABS Medical filament.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4.\u003c/strong\u003e 3D printing parameters used in the case of ABS Medical filaments\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"529\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMinimal value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMaximum value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eIdentified value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eLayer thickness [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eExtrusion width [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eNozzle temperature [\u0026deg;C]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e235\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e255\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e240\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eBed temperature [\u0026deg;C]\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eCooling option [%]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003e3D printing speed [mm/s]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eRetraction length [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eRetraction speed [mm/s]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5.\u0026nbsp;\u003c/strong\u003e Mechanical Properties of ABS Medical filament used in FFF 3D Printing Technique\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"363\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eValue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eYoung\u0026rsquo;s Modulus [MPa]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e2450\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eYield stress [MPa]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eElongation at break [%]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eBall indentation hardness [N/mm\u003csup\u003e2\u003c/sup\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eVicat softening temperature [\u0026deg;C]\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e97\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eDensity [kg/m\u0026sup3;]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e1060\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe proposed geometry of the inlet connector was designed to allow its production using the 3D printing technique without the need for additional support structures. This optimisation helped to reduce the manufacturing time. During a single technological process, four components were produced simultaneously. As in the previous case, six Prusa i3 MK3S+ 3D printers were used simultaneously for production. The approximate duration of the manufacturing process was 4 hours. Figure 18 presents a general view of the manufactured inlet connectors along with additional sealing plugs designed to fit the oxygen supply drain. The plugs were made of TPU-95 material to ensure the required level of sealing. A total of 150 connectors were produced.\u003c/p\u003e\n\u003cp\u003eThe next stage of the production process involved manufacturing diffuser components, which were installed inside the helmet using a press-fit connection. As the diffuser is a critical component of the inlet system, it was decided to fabricate it using FFF 3D printing technology, using ABS Medical filament as the material. A general view of the individual components of the diffuser is presented in Figure 19. The diffuser consists of a main body, an additional ring, and a cover. The proposed geometry and its division into three separate parts significantly optimised the manufacturing process. This modular design enabled the production of each component without the need for additional support structures, enhancing manufacturing efficiency and material use.\u003c/p\u003e\n\u003cp\u003eFigure 20. presents a main view of the manufactured components. To enhance functionality by integrating a directional valve mechanism, a parasol valve can be installed within the diffuser body. This addition prevents the reverse flow of air from the helmet to the power supply unit, ensuring proper airflow control. The production time for a single diffuser was approximately one hour. Each manufacturing cycle produced three diffuser components simultaneously. Since six 3D printers were operated in parallel, a total of 18 diffusers could be fabricated in three hours, significantly improving production efficiency. After the surface quality of the manufactured components was verified, the diffusers were assembled in their final configuration.\u003c/p\u003e\n\u003cp\u003eThe next stage in the production of a prototype batch of CPAP helmet components involved the manufacturing of PEEP valves. These valves were fabricated using SLS with polyamide powder PA 2200. Since the PEEP valves are located at the end of the air exhaust system, there is no risk of unmolten powder particles entering the helmet interior. Consequently, the use of SLS as a 3D printing technique is feasible for this application. The manufacturing process was carried out using the 3D printing process parameters listed in Table 6. They were determined based on the results of previously performed additional technological tests to achieve minimal external surface roughness, high geometric quality and high mechanical strength. Furthermore, Table 7 presents the mechanical properties of the polyamide PA 2200 powder.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 6.\u003c/strong\u003e 3D printing parameters used in the SLS technique and PA 2200 powder\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"363\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eIdentified value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eLayer thickness [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eContour speed [mm/s]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e3000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eContour Power [W]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e13.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eContour beam offset [mm]\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eHatching distance [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eHatching speed [mm/s]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e3200\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eHatching Power [W]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eHatching beam offset [mm/s]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 7.\u003c/strong\u003e Mechanical Properties of Polyamide PA 2200 powder used in the SLS 3D Printing Technique\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"363\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eValue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eYoung\u0026rsquo;s Modulus [MPa]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e1650\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eTensile Strength [MPa]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e48\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eElongation [%]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eMelting Temperature [\u0026deg;C]\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e176\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eSoftening Temperature (1.80 MPa) [\u0026deg;C]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eSoftening Temperature (0.65 MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e154\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 231px;\"\u003e\n \u003cp\u003eDensity [kg/m\u0026sup3;]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e930\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe PEEP valve manufacturing process was based on the model depicted in Figure 11. Figures 21 provide an overview of the components of the PEEP valve produced via the SLS technique.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe proposed modification of the geometric design of the connecting fittings between the CPAP helmet and the ventilator has significantly optimised their construction in terms of overall dimensions, weight, connection method and manufacturing technology. Removal of the Boston sockets, as shown in Figure 1, and their replacement with dedicated T 22F sockets - designed and dimensioned according to the EN ISO 5356-1:2015 standard - have greatly simplified the original design.\u003c/p\u003e\n\u003cp\u003eThe new socket variant, manufactured using FFF 3D printing technology with flexible Polyurethane TPU 95, replaces the threaded connection with a press-fit mechanism. This change has led to a reduction in the overall size of the air-oxygen mixture supply and the exhaust components connected to the helmet. Furthermore, eliminating the threaded connection has reduced the number of parts and removed the need for additional seals, which were previously required to minimise the risk of air leakage from the helmet.\u003c/p\u003e\n\u003cp\u003eFigures 22 and 23 present a comparison of the 3D CAD models, highlighting the overall dimensions of the components before and after modification. An additional advantage of the modified geometry of both connector variants was the reduction in their mass. In the case of the inlet connector, the mass was reduced from 85 g to 35.5 g. For the outlet connector, the mass was decreased from 120 g to 34 g.\u003c/p\u003e\n\u003cp\u003eAn additional factor contributing to the reduction in the dimensions and mass of the inlet subassembly was the implementation of a redesigned diffuser. Figure 24 presents a comparison of the 3D CAD models of both diffuser variants, along with the corresponding values of their key overall dimensions.\u003c/p\u003e\n\u003cp\u003eThis new design features significantly smaller overall dimensions, while also demonstrating enhanced operational efficiency, as validated through computational fluid dynamics (CFD) analysis. Furthermore, the integration of an umbrella valve serves as a critical improvement, enabling one-way flow control. This prevents air from escaping from the helmet into the inlet system and the connected respirator, ensuring optimal performance and safety.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors’ optimisation of helmet fitting geometry aimed to support additive manufacturing (AM), enabling rapid, tool-free production of fixture sets required for clinical trials. Small-batch fabrication allowed continuous design improvements based on experimental feedback, eliminating early-stage flaws. Iterative adjustments ensured a secure fit between fittings, the helmet, and oxygen therapy devices.\u003c/p\u003e\n\u003cp\u003eGeometric refinement of adjustable components, such as the PEEP valve regulator cap, enabled precise fitting and consistent pressure regulation. Initial production of inlet and outlet connectors used PET-G and ABS Medical with FFF 3D printing. To assess particle detachment risk under high airflow, tests were conducted, confirming that ABS Medical showed superior resistance to material erosion. Due to ABS’s sensitivity to thermal shrinkage, shielding was applied during printing to reduce air circulation and distortion.\u003c/p\u003e\n\u003cp\u003eThe redesigned diffuser significantly improved patient comfort. CFD-guided modifications to the housing geometry optimized the internal ring shape, redirecting airflow laterally for better distribution. Symmetrical positioning of ports and mounting sockets in the helmet’s lower section enhanced comfort during prolonged therapy. A one-way medical-grade silicone umbrella valve was integrated into the diffuser, preventing backflow of exhaled air into medical devices, thus increasing system safety and efficiency.\u003c/p\u003e\n\u003cp\u003eAs with other fittings, the diffuser was designed within FFF constraints. Components were optimized to eliminate the need for support structures, reducing print time, material waste, and enhancing production efficiency. SLS 3D printing is viable for external PEEP valve parts, where airflow exposure is not a concern. Additional design modifications further streamlined production by enabling direct printing with minimal post-processing.\u003c/p\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eThe presented case study on optimising the geometry of the inlet and outlet fitting elements of the CPAP helmet exemplifies a structured approach applicable to the design of novel medical equipment. The process was characterised by the integration of advanced computational design tools and state-of-the-art manufacturing techniques, particularly 3D printing. Furthermore, the methodology outlined in this study reflects the iterative nature of contemporary product development, emphasising continuous improvement through successive design refinements.\u003c/p\u003e\n\u003cp\u003eThe initial design concept, described in the study introduction, was performed based on an extensive review of the literature, patent analysis, and evaluation of existing market solutions. Taking advantage of this foundational knowledge, the first concept design of the CPAP helmet was developed as a rapid response to the urgent need for respiratory support equipment during the early stages of the COVID-19 pandemic in 2019. Given the shortage of medical devices to treat acute respiratory failure, the proposed solution played a crucial role in addressing this pressing health challenge.\u003c/p\u003e\n\u003cp\u003eSubsequent clinical trials, initially involving volunteers and later expanding to patient participants, provided critical information on the strengths and limitations of the preliminary design. The findings of these trials were fundamental in the next phase of development, which focused on addressing identified shortcomings, optimising the dimensions and weight, and simplifying the manufacturing process to improve overall efficiency and scalability. To summarise, the key modifications implemented by the authors to enhance patient comfort include:\u003c/p\u003e\n\u003cp\u003e1.\u0026nbsp; \u0026nbsp;The elimination of the proposed Boston connector significantly reduced the size of both the inlet and outlet fittings. Moreover, it considerably simplified the process of attaching the connectors to the helmet.\u003c/p\u003e\n\u003cp\u003e2.\u0026nbsp; Integration of F-22 sockets, manufactured using advanced 3D printing techniques, designed in compliance with the relevant EN ISO 5356-1:2015 standard, and subsequently bonded to CPAP helmets via vibration welding. This approach ensured a robust and reliable connection while leveraging the benefits of additive manufacturing.\u003c/p\u003e\n\u003cp\u003e3. Significant reduction in overall dimensions and weight of both inner and outer connectors by replacing the conventional threaded joint with a press-fit connection. This change contributed to improved portability and user comfort while maintaining structural integrity.\u003c/p\u003e\n\u003cp\u003e4. Optimisation of connector geometry through CAD-based modifications, carefully considering the constraints and capabilities of widely available 3D printing technologies, specifically Fused Filament Fabrication (FFF) and Selective Laser Sintering (SLS). This refinement enhanced manufacturability, ensuring precision and consistency in component production.\u003c/p\u003e\n\u003cp\u003e5.\u0026nbsp; Additional tests have demonstrated that PET-G, despite its high technological adaptability and suitability for manufacturing components intended for food contact or skin exposure, is not suitable for the production of components used in oxygen therapy. This limitation arises due to the formation of fine, hair-like structures during the 3D printing process, which are challenging to eliminate.\u003c/p\u003e\n\u003cp\u003e6.\u0026nbsp; \u0026nbsp;In contrast, ABS Medical, although susceptible to thermal shrinkage, exhibits a lower tendency to develop such technological defects. Therefore, the authors recommend its use in the manufacture of medical device components, particularly connectors used in oxygen therapy, such as the CPAP helmet connectors characterised in this study.\u003c/p\u003e\n\u003cp\u003eThe design and manufacturing approach presented in this study exemplifies an effective response to crisis scenarios, including pandemics, armed conflicts that lead to supply chain disruptions, and restricted access to essential medical treatments.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWroblewski Lukasz reports financial support was provided by Polish Ministry of Science and Higher Education, Centre for Research and Development. The grant NCBR 52/2020.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eNgo, T. D., Kashani, A., Imbalzano, G., Nguyen, K. T. Q. \u0026amp; Hui, D. Additive manufacturing (3D printing): A review of materials, methods, applications and challenges. \u003cem\u003eCompos B Eng\u003c/em\u003e \u003cstrong\u003e143\u003c/strong\u003e, 172\u0026ndash;196 (2018).\u003c/li\u003e\n\u003cli\u003eSingh, S., Singh, G., Prakash, C. \u0026amp; Ramakrishna, S. Current status and future directions of fused filament fabrication. \u003cem\u003eJ Manuf Process\u003c/em\u003e \u003cstrong\u003e55\u003c/strong\u003e, 288\u0026ndash;306 (2020).\u003c/li\u003e\n\u003cli\u003eWu, W. \u003cem\u003eet al.\u003c/em\u003e Deformation mechanism of innovative 3D chiral metamaterials. \u003cem\u003eSci Rep\u003c/em\u003e \u003cstrong\u003e8\u003c/strong\u003e, (2018).\u003c/li\u003e\n\u003cli\u003eBai, W. \u003cem\u003eet al.\u003c/em\u003e Academic insights and perspectives in 3d printing: A bibliometric review. \u003cem\u003eApplied Sciences (Switzerland)\u003c/em\u003e vol. 11 Preprint at https://doi.org/10.3390/app11188298 (2021).\u003c/li\u003e\n\u003cli\u003ePalmara, G., Frascella, F., Roppolo, I., Chiappone, A. \u0026amp; Chiad\u0026ograve;, A. Functional 3D printing: Approaches and bioapplications. \u003cem\u003eBiosens Bioelectron\u003c/em\u003e \u003cstrong\u003e175\u003c/strong\u003e, (2021).\u003c/li\u003e\n\u003cli\u003eMayo, W. \u003cem\u003eet al.\u003c/em\u003e Facial defects reconstruction by titanium mesh bending using 3D printing technology: A report of two cases. \u003cem\u003eAnnals of Medicine and Surgery\u003c/em\u003e \u003cstrong\u003e78\u003c/strong\u003e, (2022).\u003c/li\u003e\n\u003cli\u003eGuoqing, Z. \u003cem\u003eet al.\u003c/em\u003e Design Optimization and Manufacturing of Bio-fixed tibial implants using 3D printing technology. \u003cem\u003eJ Mech Behav Biomed Mater\u003c/em\u003e \u003cstrong\u003e117\u003c/strong\u003e, 104415 (2021).\u003c/li\u003e\n\u003cli\u003eRamlee, M. H. \u003cem\u003eet al.\u003c/em\u003e Investigation on three-dimensional printed prosthetics leg sockets coated with different reinforcement materials: analysis on mechanical strength and microstructural. \u003cem\u003eSci Rep\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, (2024).\u003c/li\u003e\n\u003cli\u003eHaryńska, A. \u003cem\u003eet al.\u003c/em\u003e A comprehensive evaluation of flexible FDM/FFF 3D printing filament as a potential material in medical application. \u003cem\u003eEur Polym J\u003c/em\u003e \u003cstrong\u003e138\u003c/strong\u003e, 109958 (2020).\u003c/li\u003e\n\u003cli\u003ePalmara, G., Frascella, F., Roppolo, I., Chiappone, A. \u0026amp; Chiad\u0026ograve;, A. Functional 3D printing: Approaches and bioapplications. \u003cem\u003eBiosens Bioelectron\u003c/em\u003e \u003cstrong\u003e175\u003c/strong\u003e, (2021).\u003c/li\u003e\n\u003cli\u003eKabra, A., Mehta, N. \u0026amp; Garg, B. 3D printing in spine care: A review of current applications. \u003cem\u003eJ Clin Orthop Trauma\u003c/em\u003e \u003cstrong\u003e35\u003c/strong\u003e, (2022).\u003c/li\u003e\n\u003cli\u003eHe, Y., Xue, G. H. \u0026amp; Fu, J. Z. Fabrication of low cost soft tissue prostheses with the desktop 3D printer. \u003cem\u003eSci Rep\u003c/em\u003e \u003cstrong\u003e4\u003c/strong\u003e, (2014).\u003c/li\u003e\n\u003cli\u003eZhou, L. \u003cem\u003eet al.\u003c/em\u003e Additive Manufacturing: A Comprehensive Review. \u003cem\u003eSensors\u003c/em\u003e vol. 24 Preprint at https://doi.org/10.3390/s24092668 (2024).\u003c/li\u003e\n\u003cli\u003eVakharia, V. N. \u003cem\u003eet al.\u003c/em\u003e Printing in a Pandemic: 3D printing solutions for healthcare during COVID-19. A Protocol for a PRISMA systematic review. \u003cem\u003eAnnals of 3D Printed Medicine\u003c/em\u003e vol. 2 Preprint at https://doi.org/10.1016/j.stlm.2021.100015 (2021).\u003c/li\u003e\n\u003cli\u003eManoj, A., Bhuyan, M., Raj Banik, S. \u0026amp; Ravi Sankar, M. 3D printing of nasopharyngeal swabs for COVID-19 diagnose: Past and current trends. in \u003cem\u003eMaterials Today: Proceedings\u003c/em\u003e vol. 44 1361\u0026ndash;1368 (Elsevier Ltd, 2021).\u003c/li\u003e\n\u003cli\u003eArjunan, A., Zahid, S., Baroutaji, A. \u0026amp; Robinson, J. 3D printed auxetic nasopharyngeal swabs for COVID-19 sample collection. \u003cem\u003eJ Mech Behav Biomed Mater\u003c/em\u003e \u003cstrong\u003e114\u003c/strong\u003e, 104175 (2021).\u003c/li\u003e\n\u003cli\u003ePłatek, P. \u003cem\u003eet al.\u003c/em\u003e 3D Printing in the Fight Against Covid-19. \u003cem\u003eMedical Devices: Evidence and Research\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 167\u0026ndash;182 (2023).\u003c/li\u003e\n\u003cli\u003eWooldridge, A. R., Carman, E. M. \u0026amp; Xie, A. Human Factors and Ergonomics (HFE) applications in responses to the COVID-19 pandemic: Lessons learned and considerations for methods. \u003cem\u003eAppl Ergon\u003c/em\u003e \u003cstrong\u003e102\u003c/strong\u003e, (2022).\u003c/li\u003e\n\u003cli\u003eNold, J. \u003cem\u003eet al.\u003c/em\u003e Air seal performance of personalized and statistically shaped 3D-printed face masks compared with market-available surgical and FFP2 masks. \u003cem\u003eSci Rep\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, (2021).\u003c/li\u003e\n\u003cli\u003eChoong, Y. Y. C. \u003cem\u003eet al.\u003c/em\u003e The global rise of 3D printing during the COVID-19 pandemic. \u003cem\u003eNature Reviews Materials\u003c/em\u003e vol. 5 637\u0026ndash;639 Preprint at https://doi.org/10.1038/s41578-020-00234-3 (2020).\u003c/li\u003e\n\u003cli\u003eManero, A. \u003cem\u003eet al.\u003c/em\u003e Leveraging 3D printing capacity in times of crisis: Recommendations for COVID-19 distributed manufacturing for medical equipment rapid response. \u003cem\u003eInt J Environ Res Public Health\u003c/em\u003e \u003cstrong\u003e17\u003c/strong\u003e, 1\u0026ndash;17 (2020).\u003c/li\u003e\n\u003cli\u003eVordos, N. \u003cem\u003eet al.\u003c/em\u003e How 3D printing and social media tackles the PPE shortage during Covid \u0026ndash; 19 pandemic. \u003cem\u003eSaf Sci\u003c/em\u003e \u003cstrong\u003e130\u003c/strong\u003e, 104870 (2020).\u003c/li\u003e\n\u003cli\u003eOladapo, B. I., Ismail, S. O., Afolalu, T. D., Olawade, D. B. \u0026amp; Zahedi, M. Review on 3D printing: Fight against COVID-19. \u003cem\u003eMater Chem Phys\u003c/em\u003e \u003cstrong\u003e258\u003c/strong\u003e, 123943 (2021).\u003c/li\u003e\n\u003cli\u003eArmani, A. M., Hurt, D. E., Hwang, D., McCarthy, M. C. \u0026amp; Scholtz, A. Low-tech solutions for the COVID-19 supply chain crisis. \u003cem\u003eNature Reviews Materials\u003c/em\u003e vol. 5 403\u0026ndash;406 Preprint at https://doi.org/10.1038/s41578-020-0205-1 (2020).\u003c/li\u003e\n\u003cli\u003eSalmi, M. \u003cem\u003eet al.\u003c/em\u003e 3D printing in COVID-19: Productivity estimation of the most promising open source solutions in emergency situations. \u003cem\u003eApplied Sciences (Switzerland)\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 1\u0026ndash;15 (2020).\u003c/li\u003e\n\u003cli\u003eJafferson, JM. \u0026amp; Pattanashetti, S. Use of 3D printing in production of personal protective equipment (PPE) - a review. \u003cem\u003eMater Today Proc\u003c/em\u003e (2021) doi:10.1016/j.matpr.2021.02.072.\u003c/li\u003e\n\u003cli\u003eManoj, A., Bhuyan, M., Raj Banik, S. \u0026amp; Ravi Sankar, M. 3D printing of nasopharyngeal swabs for COVID-19 diagnose: Past and current trends. \u003cem\u003eMater Today Proc\u003c/em\u003e (2020) doi:10.1016/j.matpr.2020.11.505.\u003c/li\u003e\n\u003cli\u003ePedraja, J. \u003cem\u003eet al.\u003c/em\u003e Role of 3D printing in the protection of surgical and critical care professionals in the COVID-19 pandemic. \u003cem\u003eRevista Espa\u0026ntilde;ola de Anestesiolog\u0026iacute;a y Reanimaci\u0026oacute;n (English Edition)\u003c/em\u003e \u003cstrong\u003e67\u003c/strong\u003e, 417\u0026ndash;424 (2020).\u003c/li\u003e\n\u003cli\u003eJafferson, JM. \u0026amp; Pattanashetti, S. Use of 3D printing in production of personal protective equipment (PPE) - a review. \u003cem\u003eMater Today Proc\u003c/em\u003e (2021) doi:10.1016/j.matpr.2021.02.072.\u003c/li\u003e\n\u003cli\u003eJanson, D. J., Clift, B. C. \u0026amp; Dhokia, V. PPE fit of healthcare workers during the COVID-19 pandemic. \u003cem\u003eAppl Ergon\u003c/em\u003e \u003cstrong\u003e99\u003c/strong\u003e, (2022).\u003c/li\u003e\n\u003cli\u003eKalyniuk, N. M., Franchuk, V. V., Selskyy, P. R., Humenna, N. V. \u0026amp; Hladii, O. I. Blended form of education as an innovative approach in the training of medical students: The experience of Ukraine. \u003cem\u003eEducacion Medica\u003c/em\u003e \u003cstrong\u003e25\u003c/strong\u003e, (2024).\u003c/li\u003e\n\u003cli\u003eAlzhrani, R. F., Alyahya, M. Y., Algahtani, M. S., Fitaihi, R. A. \u0026amp; Tawfik, E. A. Trend of pharmaceuticals 3D printing in the Middle East and North Africa (MENA) region: An overview, regulatory perspective and future outlook. \u003cem\u003eSaudi Pharmaceutical Journal\u003c/em\u003e \u003cstrong\u003e32\u003c/strong\u003e, (2024).\u003c/li\u003e\n\u003cli\u003ePedraja, J. \u003cem\u003eet al.\u003c/em\u003e Role of 3D printing in the protection of surgical and critical care professionals in the COVID-19 pandemic. \u003cem\u003eRevista Espa\u0026ntilde;ola de Anestesiolog\u0026iacute;a y Reanimaci\u0026oacute;n (English Edition)\u003c/em\u003e \u003cstrong\u003e67\u003c/strong\u003e, 417\u0026ndash;424 (2020).\u003c/li\u003e\n\u003cli\u003eSalmi, M. \u003cem\u003eet al.\u003c/em\u003e 3D printing in COVID-19: Productivity estimation of the most promising open source solutions in emergency situations. \u003cem\u003eApplied Sciences (Switzerland)\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 1\u0026ndash;15 (2020).\u003c/li\u003e\n\u003cli\u003eTareq, M. S., Rahman, T., Hossain, M. \u0026amp; Dorrington, P. Additive manufacturing and the COVID-19 challenges: An in-depth study. \u003cem\u003eJ Manuf Syst\u003c/em\u003e (2021) doi:10.1016/j.jmsy.2020.12.021.\u003c/li\u003e\n\u003cli\u003eBibiano-Guillen, C. \u003cem\u003eet al.\u003c/em\u003e Adapted Diving Mask (ADM) device as respiratory support with oxygen output during COVID-19 pandemic. \u003cem\u003eAmerican Journal of Emergency Medicine\u003c/em\u003e \u003cstrong\u003e39\u003c/strong\u003e, 42\u0026ndash;47 (2021).\u003c/li\u003e\n\u003cli\u003eVordos, N. \u003cem\u003eet al.\u003c/em\u003e How 3D printing and social media tackles the PPE shortage during Covid \u0026ndash; 19 pandemic. \u003cem\u003eSaf Sci\u003c/em\u003e \u003cstrong\u003e130\u003c/strong\u003e, 104870 (2020).\u003c/li\u003e\n\u003cli\u003eMaracaja, L., Blitz, D., Maracaja, D. L. V. \u0026amp; Walker, C. A. How 3D Printing Can Prevent Spread of COVID-19 Among Healthcare Professionals During Times of Critical Shortage of Protective Personal Equipment. \u003cem\u003eJ Cardiothorac Vasc Anesth\u003c/em\u003e \u003cstrong\u003e34\u003c/strong\u003e, 2847\u0026ndash;2849 (2020).\u003c/li\u003e\n\u003cli\u003eBallard, D. H. \u003cem\u003eet al.\u003c/em\u003e Quantitative Fit Tested N95 Respirator-Alternatives Generated With CT Imaging and 3D Printing: A Response to Potential Shortages During the COVID-19 Pandemic. \u003cem\u003eAcad Radiol\u003c/em\u003e \u003cstrong\u003e28\u003c/strong\u003e, 158\u0026ndash;165 (2021).\u003c/li\u003e\n\u003cli\u003eSingh, S., Prakash, C. \u0026amp; Ramakrishna, S. Three-dimensional printing in the fight against novel virus COVID-19: Technology helping society during an infectious disease pandemic. \u003cem\u003eTechnol Soc\u003c/em\u003e \u003cstrong\u003e62\u003c/strong\u003e, 101305 (2020).\u003c/li\u003e\n\u003cli\u003eAmirfarzan, H. \u003cem\u003eet al.\u003c/em\u003e Use of Helmet CPAP in COVID-19 \u0026ndash; A practical review. \u003cem\u003ePulmonology\u003c/em\u003e (2021) doi:10.1016/j.pulmoe.2021.01.008.\u003c/li\u003e\n\u003cli\u003eAliberti, S. \u003cem\u003eet al.\u003c/em\u003e Helmet CPAP treatment in patients with COVID-19 pneumonia: a multicentre cohort study. \u003cem\u003eEur Respir J\u003c/em\u003e \u003cstrong\u003e56\u003c/strong\u003e, (2020).\u003c/li\u003e\n\u003cli\u003eAnaesthetic and respiratory equipment \u0026mdash; Conical connectors \u0026mdash; Part 1: Cones and sockets. \u003cem\u003eISO 5356-1:2015(E)\u003c/em\u003e \u003cstrong\u003e2015\u003c/strong\u003e, (2015).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Footnotes","content":"\u003cp\u003e\u003csup\u003e[1]\u003c/sup\u003e https://sklep.spectrumfilaments.com/product-pol-1257-Filament-Spectrum-ABS-Medical-1-75mm-1kg.html\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e[2]\u003c/sup\u003e https://sklep.spectrumfilaments.com/product-pol-1259-Filament-Spectrum-PET-G-FX120-1-75mm-NATURAL-1kg.html\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"additive manufacturing, 3D printing, hCPAP, ergonomic studies, COVID-19","lastPublishedDoi":"10.21203/rs.3.rs-6388720/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6388720/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"This study presents the geometrical optimisation of fitting connectors to a Continuous Positive Airway Pressure (CPAP) helmet for use with a ventilator in the treatment of acute respiratory failure. The initial design, developed in 2019 during the COVID-19 pandemic, underwent several optimisation stages. The goal was to reduce the size and weight of air supply and exhaust fittings while improving manufacturability via 3D printing. Two additive manufacturing (AM) techniques were evaluated: Fused Filament Fabrication (FFF) and Laser Powder Bed Fusion of polymers (PBF-LB/P). Experimental tests assessed the risk of microplastic particle detachment from components printed with medically approved PET-G and ABS-Medical filaments. ABS-Medical proved the most suitable, demonstrating reduced susceptibility to hairline structure formation during printing. The final optimised geometry, significantly smaller and lighter, was adapted to the selected AM processes. As a result, approximately 150 CPAP helmet fittings were produced and tested in clinical trials.","manuscriptTitle":"Design, Manufacturing, and Testing of 3D-Printed Fittings for Helmet Continuous Positive Airway Pressure Medical Device: A Case Study in Ergonomic Optimisation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-14 11:30:36","doi":"10.21203/rs.3.rs-6388720/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-06-03T07:38:13+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-30T19:16:01+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-21T16:57:05+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-09T12:08:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-09T08:41:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"75722458274170361276354614263573457379","date":"2025-05-06T11:57:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"10905960102502296563640773336828760819","date":"2025-05-06T10:33:32+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"24833346225658330411192626876834547903","date":"2025-05-04T17:00:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"266478384431211306223865009419063353884","date":"2025-05-03T18:49:46+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"265298261439021289362524068114841521422","date":"2025-05-02T08:13:39+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-01T12:45:54+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-23T10:36:54+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-18T20:20:48+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-04-18T20:19:40+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"50905417-388b-4e7f-ae40-fa9ec561c0fa","owner":[],"postedDate":"May 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":48045397,"name":"Health sciences/Medical research"},{"id":48045398,"name":"Physical sciences/Materials science/Biomaterials"},{"id":48045399,"name":"Physical sciences/Materials science/Materials for devices"},{"id":48045400,"name":"Health sciences/Health care"},{"id":48045401,"name":"Health sciences/Health care/Disease prevention"},{"id":48045402,"name":"Physical sciences/Engineering/Biomedical engineering"},{"id":48045403,"name":"Physical sciences/Engineering/Mechanical engineering"}],"tags":[],"updatedAt":"2025-12-01T16:09:38+00:00","versionOfRecord":{"articleIdentity":"rs-6388720","link":"https://doi.org/10.1038/s41598-025-25851-2","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-11-25 15:57:50","publishedOnDateReadable":"November 25th, 2025"},"versionCreatedAt":"2025-05-14 11:30:36","video":"","vorDoi":"10.1038/s41598-025-25851-2","vorDoiUrl":"https://doi.org/10.1038/s41598-025-25851-2","workflowStages":[]},"version":"v1","identity":"rs-6388720","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6388720","identity":"rs-6388720","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}