Evaluation of the usefulness and safety of percutaneous CO2 monitoring during bronchoscopic intervention

Evaluation of the usefulness and safety of percutaneous CO2 monitoring during bronchoscopic intervention | 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 Evaluation of the usefulness and safety of percutaneous CO 2 monitoring during bronchoscopic intervention Yu Numata, Hajime Tsuruoka, Hiroshi Handa, Kazuhiro Nishiyama, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6547703/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Background End-tidal carbon dioxide (ETCO₂) monitoring is limited during rigid bronchoscopic procedures due to open airway conditions. This study aimed to evaluate the utility and safety of transcutaneous carbon dioxide (TcCO₂) monitoring as a surrogate for arterial CO₂ (PaCO₂) during therapeutic bronchoscopy. Methods In this prospective observational study, adult patients undergoing rigid bronchoscopy between June 2024 and January 2025 were enrolled. TcCO₂ was continuously monitored using the Sentec Digital Monitoring System. Arterial blood gas samples were collected at 7.5, 15, and 35 minutes after intervention initiation. Spearman’s rank correlation and Bland-Altman analyses were used to assess agreement between TcCO₂ and PaCO₂, and between SpO₂ and SaO₂. Results Thirty patients were analysed. Mean PaCO₂ increased over time, while TcCO₂ peaked at 15 minutes. Strong correlations were observed between PaCO₂ and TcCO₂ (ρ = 0.86–0.89, p < 0.001) and between SaO₂ and SpO₂ (ρ = 0.81–0.84, p < 0.001). Bland-Altman analysis confirmed good agreement at all time points for both gas exchange pairs. Conclusion TcCO₂ monitoring is a reliable, non-invasive alternative to PaCO₂ measurement during rigid bronchoscopy. It provides real-time ventilation assessment in settings where ETCO₂ monitoring is not feasible, supporting its clinical integration. Health sciences/Medical research Health sciences/Medical research/Study design Arterial carbon dioxide (PaCO₂) rigid bronchoscopy SpO₂ transcutaneous carbon dioxide (TcCO₂) ventilation monitoring Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction End-tidal carbon dioxide (ETCO₂) is commonly monitored during general anaesthesia as an indicator of carbon dioxide (CO₂) accumulation and ventilation adequacy 1 . In general, therapeutic bronchoscopy procedures, including laser therapy, argon plasma coagulation (APC), balloon dilation, and airway stenting, are performed under general anaesthesia using a rigid bronchoscope 2 . Okamoto et al. reported that oxygenation tends to be maintained when spontaneous breathing is halted through muscle relaxants; however, the risk of laryngospasm during extubating remains a concern 3 . At our institution, therapeutic bronchoscopy procedures are performed while preserving spontaneous breathing, as maintaining oxygenation may be challenging in apnoeic conditions. This approach requires highly skilled anesthetic management to appropriately balance anesthetic depth and spontaneous respiration. During rigid bronchoscopy, the airway remains open, complicating the measurement of ETCO₂. Consequently, pulse oxygenation (SpO₂) often serves as the only available parameter to evaluate ventilation. We previously reported on the feasibility and safety of transcutaneous CO₂ (TcCO 2 ) monitoring during bronchoscopic interventions 4 . In the current study, we hypothesized that TcCO₂ monitoring could provide a reliable method for assessing ventilation status during therapeutic bronchoscopic procedures. Therefore, the aim of this study was to evaluate the utility and safety of TcCO₂ measurements as a surrogate for partial pressure CO 2 (PaCO₂) and as an assessment tool for ventilation dynamics during therapeutic bronchoscopic interventions. Results Patient Characteristics and Interventions Initially, 42 patients were recruited for this study; however, 12 patients were subsequently excluded, leaving 30 patients enrolled in the final analysis. Exclusion reasons included TcCO₂ measurement failure (n = 8), loss of spontaneous breathing due to muscle relaxant administration (n = 2), and initiation of the intervention before the start of TcCO₂ monitoring (n = 2). Among measurement failures, three were caused by difficulty attaching the sensor due to auricular dryness, while five resulted from calibration issues ( Fig. 1 ). Patient demographics and clinical characteristics, including sex, age, height, weight, BMI, underlying conditions, and procedures performed, are detailed in Table 1 . The median age was 71 years (range: 33–86 years), and 46.7% (n = 14) were male. The mean BMI was 19.4 ± 3.8 kg/m². Lung cancer was the most common underlying condition (n = 16), followed by esophageal cancer (n = 5), chronic obstructive pulmonary disease (COPD; n = 5), and endobronchial tuberculosis (n = 5). Other diagnoses included tracheoesophageal fistula (n = 2), iatrogenic subglottic stenosis (n = 2), tracheal polyp (n = 1), and malignant mediastinal tumour (n = 1). Several patients presented with multiple overlapping diagnoses. Table 1 Patient demographics, underlying diseases, and procedures performed Patient Characteristics Age (years), Median (range) 71 (33–86) Sex, n (%), Male / Female 14 (46.7) / 16 (53.3) BMI (kg/m²), Mean ± SD 19.4 ± 3.8 Underlying Diseases, n Lung cancer 16 Esophageal cancer 5 Tracheoesophageal fistula 2 Endobronchial tuberculosis 5 Iatrogenic subglottic stenosis 2 COPD 5 Tracheal polyp 1 Malignant mediastinal tumor 1 Procedures Performed, n Airway stent placement 16 Argon plasma coagulation 7 Balloon dilation 5 Stent removal 6 Tumor resection 4 Abbreviations: BMI, body mass index; COPD, chronic obstructive pulmonary disease; SD, standard deviation. The most frequently performed procedure was airway stent placement (n = 16), followed by APC (n = 7), stent removal (n = 6), balloon dilation (n = 5), and tumour resection (n = 4). Some patients underwent multiple procedures. Supplementary Table S1 provides detailed individual patient data. Changes in PaCO₂ and TcCO₂ during Intervention The trends and statistical results of PaCO₂ and TcCO₂ are summarized in Table 2 . Mean PaCO₂ values were 54.30 ± 12.50 Torr at 7.5 minutes, 56.70 ± 15.10 Torr at 15 minutes, and 63.20 ± 21.10 Torr at 35 minutes after initiation of the intervention, showing a gradual increase over time. In contrast, mean TcCO₂ values were 53.92 ± 13.19 Torr at 7.5 minutes, peaked at 60.13 ± 14.93 Torr at 15 minutes, and then slightly decreased to 57.97 ± 18.88 Torr at 35 minutes ( Fig. 2 ). Overall, both PaCO₂ and TcCO₂ remained elevated throughout the procedure. Table 2 Temporal changes and descriptive statistics of PaCO₂ and TcCO₂ measurements. Time 7.5–35 min 7.5 min 15 min 35 min PaCO₂, Torr Mean ± SD 57.21 ± 16.29 54.30 ± 12.50 56.70 ± 15.10 63.20 ± 21.10 Median 55.1 54.2 56.1 59.65 Max 118.4 90.6 100.3 118.4 Min 30.1 30.1 32.1 42 Range 88.3 60.5 68.2 76.4 TcCO₂, Torr Mean ± SD 57.57 ± 15.42 53.92 ± 13.19 60.13 ± 14.93 57.97 ± 18.88 Median 53.75 54 59.85 53 Max 118.4 80.7 87.6 118.4 Min 27.8 27.8 28.6 30.6 Range 90.6 52.9 59 87.8 Abbreviations: Min, minutes; PaCO₂, partial pressure of carbon dioxide; SD, standard deviation; TcCO₂, transcutaneous carbon dioxide. Correlation Analysis of Gas Monitoring Parameters Strong correlations were observed between PaCO₂ and TcCO₂, as well as between SaO₂ and SpO₂ at each measured time point and throughout the overall monitoring period. Spearman's rank correlation coefficients (ρ) between PaCO₂ and TcCO 2 were 0.87 at 7.5 minutes, 0.89 at 15 minutes, 0.86 at 35 minutes, and 0.88 overall (7.5–35 minutes) ( Fig. 3 ) . Similarly, correlation coefficients between SaO₂ and SpO 2 were 0.82 at 7.5 minutes, 0.84 at 15 minutes, 0.81 at 35 minutes, and 0.83 overall (7.5–35 minutes) ( Fig. 4 ). All correlations were statistically significant (p < 0.001). Agreement Analysis of Monitoring Parameters Bland-Altman analysis demonstrated good agreement between both PaCO₂ and TcCO₂, as well as SaO₂ and SpO₂ across all measured time points. For PaCO₂ and TcCO₂, the mean differences were -0.95 mmHg at 7.5 minutes (limits of agreement: -21.76 to 19.86 mmHg), -1.22 mmHg at 15 minutes (-21.81 to 19.37 mmHg), and 5.24 mmHg at 35 minutes (-30.38 to 40.86 mmHg). When combining all time points (7.5–35 minutes), the mean difference was 0.05 mmHg (-29.96 to 30.06 mmHg), indicating consistent agreement across the dataset ( Fig. 5 ) . For SaO₂ and SpO₂, the mean differences were − 0.45% at 7.5 minutes (-7.99 to 7.10%), 0.17% at 15 minutes (-5.65 to 5.99%), and 0.11% at 35 minutes (-4.20 to 4.42%). The overall mean difference for all time points was − 0.09% (-6.76 to 6.58%), confirming high concordance throughout the procedure ( Fig. 6 ) . Discussion This study demonstrated that TcCO₂ is an effective surrogate for PaCO₂ monitoring during rigid bronchoscopic interventions. While previous publications have been limited to case reports 5 , this study contributes prospective evidence supporting the utility of TcCO₂. Strong correlations were observed between PaCO₂ and TcCO₂ at all measured time points, and SpO₂ also showed high concordance with SaO₂. These findings suggest that TcCO₂ might be a reliable alternative for ventilation monitoring in clinical situations where ETCO₂ measurement is impractical. In prior studies of rigid bronchoscopy in paediatric populations, PaCO₂ levels were frequently elevated, with higher intraprocedural CO 2 levels associated with delayed ICU discharge 6 . In our study, similarly high PaCO 2 and TcCO 2 values were observed (maximum: 118.4 Torr for both). Despite these elevations, all patients were successfully weaned from the ICU on the following day. Although the sample size was limited and no complications were observed, these findings suggest that continuous TcCO₂ monitoring may support early identification and prevention of CO 2 -related complications. Previous reports have evaluated ETCO 2 monitoring during adult rigid bronchoscopy under high-frequency jet ventilation (HFJV) 7 – 9 . However, ETCO 2 measurement under HFJV often requires brief pauses or reduced respiratory rates, leading to transient hypoventilation. Our findings suggest that for procedures performed with preserved spontaneous respiration, TcCO₂ provides valuable real-time information on ventilatory status and may enhance procedural safety. Although ETCO₂ and PaCO₂ have been shown to correlate in patients with COPD, ETCO₂ generally underestimates PaCO₂, often resulting in clinically relevant discrepancies 10 . In this study, five of 30 patients had COPD, but no discrepancies were observed between TcCO 2 and PaCO 2 . These findings indicate that TcCO 2 is a useful tool for CO 2 monitoring not only in rigid bronchoscopy but potentially in other procedures involving COPD patients. The Sentec Digital Monitoring System, used in this study has shown strong agreement with PaCO₂ in prior research 11 – 13 . Its stable sensor attachment and rapid response characteristics make it particularly suited for intraoperative use 14 . Although rare issues with calibration and auricular attachment occurred, the sensor was generally well-tolerated. Limitations This study has several limitations. The sample size was relatively small, which may limit the generalizability of the findings. Second, the duration of most procedures was short, reducing the ability to assess TcCO₂ performance during prolonged interventions. Third, while TcCO₂ and PaCO₂ showed strong agreement, the potential influence of peripheral perfusion and sensor placement variability was not fully explored. Future studies should evaluate TcCO₂ monitoring in longer procedures, in patients with unstable circulatory status, and in critically ill populations. Additional research is also needed to assess its impact on clinical outcomes and decision-making. Conclusion TcCO₂ monitoring showed good agreement with PaCO₂ and may offer a practical, non-invasive method for assessing ventilation status during rigid bronchoscopy. These findings suggest that TcCO₂ could be a useful alternative in situations where ETCO₂ monitoring is not feasible. Methods Study Design This prospective observational study was conducted between June 2024 and January 2025 at St. Marianna University. Patients underwent therapeutic bronchoscopy procedures including airway stent placement, APC, balloon dilation, stent removal, and tumour resection. This study is in accordance with the ethical principles outlined of the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of St. Marianna University School of Medicine (HREC No. 6482). All participants provided informed written consent, including consent for publication, regarding all interventions. Monitoring and Procedure s The Sentec Digital Monitoring System (TOKIBO Co., Ltd., Tokyo, Japan) was employed for TcCO₂ monitoring. Patients were positioned in the supine position, and a sensor was attached to the auricle to begin recording. An anaesthesiologist placed a radial arterial line (A-line) for continuous blood pressure monitoring and arterial blood gas sampling. Arterial blood samples were collected at 7.5, 15 and 35 minutes after initiation of the intervention. A rigid bronchoscope (EFRE-Dumon, EFER Medical, La Ciotat, France) was intubated in cases of central airway obstruction. All patients received intravenous anaesthesia with propofol and remifentanil. Baseline Monitoring and Data Collection The time of rigid bronchoscope insertion past the vocal cords was defined as the starting point for physiological monitoring, and monitoring continued until the procedure concluded. Recorded parameters included TcCO₂, PaCO₂, SpO₂, PaO₂ and SaO₂. Statistical Analysis Descriptive statistics, including mean and standard deviation (SD) were calculated for each parameter. Correlation coefficients between TcCO₂ and PaCO₂, and between SaO₂ and SpO₂ at each time point, were assessed using Spearman’s rank correlation. Agreement between TcCO₂ and PaCO₂, as well as between SaO₂ and SpO₂, was evaluated using Bland-Altman analysis. All statistical analyses were performed using JMP software version 17 (SAS Institution, Cary, NC, USA). Declarations Acknowledgements The authors would like to thank Jason Tonge for the English language review of this manuscript. Author contributions Y. N. had full access to data presented and takes responsibility for the integrity and accuracy of data analysis. H. T., H. H., K. N., and Y. S. contributed to bronchoscopic examinations and interpretation of findings. Y. N., H. H., K. M., and M. M. contributed to scientific review and approved the final manuscript. All authors read and approved the final manuscript. Data availability The datasets generated and analysed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare no competing interests. References Bhavani-Shankar, K., Moseley, H., Kumar, A. Y. & Delph, Y. Capnometry and anaesthesia. Can. J. Anaesth. 39 , 617–632 (1992). Dutau, H., Vandemoortele, T. & Breen, D. P. Rigid bronchoscopy. Clin. Chest Med. 34 , 427–435 (2013). Okamoto, S. et al. Anesthesia for rigid bronchoscopy: The impact of muscle relaxants. Anesth. Analg . 131 , 893–900 (2020). Shinozaki, Y. et al. A prospective observation study of the dynamic monitoring of transcutaneous arterial blood oxygen saturation and carbon dioxide during bronchoscopy. Respir Res. 25 , 74 (2024). Gaunt, A., Jaggar, S. I. & Morgan, C. End-tidal capnography in rigid bronchoscopy. Anaesthesia 57 , 1039–1040 (2002). Bordini, M. et al. Transcutaneous carbon dioxide monitoring in children undergoing rigid bronchoscopy: a prospective blinded observational study. Can. J. Anaesth. 72 , 273–284 (2025). Frietsch, T., Krafft, P., Becker, H. D., Buelzebruck, H. & Wiedemann, K. Intermittent capnography during high-frequency jet ventilation for prolonged rigid bronchoscopy. Acta Anaesthesiol. Scand. 44 , 391–397 (2000). Chhajed, P. N. et al. Measurement of combined oximetry and cutaneous capnography during flexible bronchoscopy. Eur. Respir J. 28 , 386–390 (2006). Simon, M. et al. Comparison of transcutaneous and end-tidal CO₂-monitoring for rigid bronchoscopy during high-frequency jet ventilation. Acta Anaesthesiol. Scand. 47 , 861–867 (2003). Tyagi, D., Govindagoudar, M. B., Jakka, S., Chandra, S. & Chaudhry, D. Correlation of PaCO₂ and ETCO₂ in COPD patients with exacerbation on mechanical ventilation. Indian J. Crit. Care Med. 25 , 305–309 (2021). Lermuzeaux, M. et al. Superiority of transcutaneous CO₂ over end-tidal CO₂ measurement for monitoring respiratory failure in nonintubated patients: A pilot study. J. Crit. Care . 31 , 150–156 (2016). van Wijk, J. J., van Weteringen, W., Hoeks, S. E. & Staals, L. M. Validation of a new combined transcutaneous tcPCO₂ and tcPO₂ sensor in children in the operating theater. Paediatr. Anaesth. 32 , 429–435 (2022). Urbano, J. et al. Accuracy of three transcutaneous carbon dioxide monitors in critically ill children. Pediatr. Pulmonol. 45 , 481–486 (2010). Domingo, C. et al. Optimal clinical time for reliable measurement of transcutaneous CO₂ with ear probes: counterbalancing overshoot and the vasodilatation effect. Sens. (Basel) . 10 , 491–500 (2010). Additional Declarations No competing interests reported. Supplementary Files TableS1..docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 19 Feb, 2026 Reviews received at journal 29 Jan, 2026 Reviews received at journal 25 Jan, 2026 Reviewers agreed at journal 12 Jan, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers invited by journal 07 Jan, 2026 Editor assigned by journal 08 Aug, 2025 Editor invited by journal 14 May, 2025 Submission checks completed at journal 14 May, 2025 First submitted to journal 28 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. 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05:55:31","extension":"png","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":19677,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/37f85b145321ad3ab08aab68.png"},{"id":100008671,"identity":"f0dd28fd-f910-487c-8eca-b9b1cfec89aa","added_by":"auto","created_at":"2026-01-12 05:55:31","extension":"png","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":28873,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/ab0e8085dee92bdcdf389a48.png"},{"id":100008675,"identity":"546bedd9-72fb-4eb8-a0a3-269563f2b49f","added_by":"auto","created_at":"2026-01-12 05:55:31","extension":"png","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":24868,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/e5796ae0c2fe8cec7547b16f.png"},{"id":100361725,"identity":"9f9f9dc5-e0f8-46a0-a1ec-17e540e0d925","added_by":"auto","created_at":"2026-01-16 07:45:36","extension":"xml","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":56754,"visible":true,"origin":"","legend":"","description":"","filename":"2b7cb2b7a5564736bd134f9aa4c10f791structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/06a9d89cd08564ce05ffc043.xml"},{"id":100008666,"identity":"754a0729-572f-471b-8725-2bc54ab674ac","added_by":"auto","created_at":"2026-01-12 05:55:30","extension":"html","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":65563,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/83294750d4002ec3f9911713.html"},{"id":100008653,"identity":"b52f6ff7-135a-422a-b2fc-ea280b8963b6","added_by":"auto","created_at":"2026-01-12 05:55:30","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":152319,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart of patient enrolment, exclusion, and final analysis. A total of 42 patients were initially enrolled. Twelve patients were excluded: two due to loss of spontaneous breathing (muscle relaxant use), two due to intervention initiation before TcCO₂ monitoring, and eight due to TcCO₂ measurement failure (three with auricular dryness, five with calibration failure). Thirty patients were included in the final analysis.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/81e6e3a91fe150fc461effd9.png"},{"id":100008658,"identity":"c3247b0f-e16e-4e5e-9f09-256d24590fcf","added_by":"auto","created_at":"2026-01-12 05:55:30","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":150339,"visible":true,"origin":"","legend":"\u003cp\u003eChanges in PaCO₂ and TcCO₂ over time during rigid bronchoscopic procedures. Line graph shows mean ± standard deviation (SD) of PaCO₂ and TcCO₂ values at 7.5, 15, and 35 minutes after intervention initiation. PaCO₂ values gradually increased, while TcCO₂ peaked at 15 minutes and slightly declined thereafter.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/c9dedfd83f6bdeae47d5779f.png"},{"id":100361761,"identity":"1df4bf88-d0db-4b59-bdde-4bd12aa84cce","added_by":"auto","created_at":"2026-01-16 07:45:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":199375,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between PaCO₂ and TcCO₂ at individual time points. Scatter plots with linear regression lines show significant correlations between PaCO₂ and TcCO₂ at 7.5 minutes (A), 15 minutes (B), 35 minutes (C), and across the overall 7.5-35-minute period (D). Spearman’s ρ ranged from 0.86 to 0.89 (p \u0026lt; 0.001 for all).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/735b562e0d6bbf63d86c3565.png"},{"id":100008656,"identity":"d6fb93c6-4b6f-4e43-86ba-46b0da689319","added_by":"auto","created_at":"2026-01-12 05:55:30","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":197029,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between SaO₂ and SpO₂ at individual time points. Scatter plots with regression lines display significant correlations at 7.5 minutes (A), 15 minutes (B), 35 minutes (C), and overall (D). Spearman’s ρ ranged from 0.81 to 0.84 (p \u0026lt; 0.001 for all).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/80036d597a4a0208349af60b.png"},{"id":100008668,"identity":"51c4eb19-75de-49da-832d-9767e8b4398d","added_by":"auto","created_at":"2026-01-12 05:55:31","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":240574,"visible":true,"origin":"","legend":"\u003cp\u003eBland-Altman plots comparing PaCO₂ and TcCO₂. Each panel shows the difference between PaCO₂ and TcCO₂ plotted against their mean at 7.5 minutes (A), 15 minutes (B), 35 minutes (C), and across all time points (D). The solid line indicates the mean difference; dashed lines indicate the limits of agreement (±1.96 SD).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/4dfd62847e2b1daf217b7dc2.png"},{"id":100008664,"identity":"fed45471-94a6-4635-88ff-7900d5020c3f","added_by":"auto","created_at":"2026-01-12 05:55:30","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":244018,"visible":true,"origin":"","legend":"\u003cp\u003eBland-Altman plots comparing SaO₂ and SpO₂. Differences are plotted against the mean of paired values at 7.5 minutes (A), 15 minutes (B), 35 minutes (C), and all time points combined (D). The solid line represents the mean difference, and dashed lines indicate the limits of agreement (±1.96 SD).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/00c6dc84636877fc96a81f8f.png"},{"id":100381303,"identity":"620c74db-7e79-4f8c-82ff-03c575458478","added_by":"auto","created_at":"2026-01-16 10:38:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1830433,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/0865ace4-f1d0-4c14-befe-47a8a8a03175.pdf"},{"id":100360487,"identity":"37a34b4f-a3cf-421b-9739-a1e12b27fffd","added_by":"auto","created_at":"2026-01-16 07:38:54","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":21663,"visible":true,"origin":"","legend":"","description":"","filename":"TableS1..docx","url":"https://assets-eu.researchsquare.com/files/rs-6547703/v1/d42fa90238c5adccc983f1d8.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eEvaluation of the usefulness and safety of percutaneous CO\u003csub\u003e2\u003c/sub\u003e monitoring during bronchoscopic intervention\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eEnd-tidal carbon dioxide (ETCO₂) is commonly monitored during general anaesthesia as an indicator of carbon dioxide (CO₂) accumulation and ventilation adequacy\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. In general, therapeutic bronchoscopy procedures, including laser therapy, argon plasma coagulation (APC), balloon dilation, and airway stenting, are performed under general anaesthesia using a rigid bronchoscope\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOkamoto et al. reported that oxygenation tends to be maintained when spontaneous breathing is halted through muscle relaxants; however, the risk of laryngospasm during extubating remains a concern\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. At our institution, therapeutic bronchoscopy procedures are performed while preserving spontaneous breathing, as maintaining oxygenation may be challenging in apnoeic conditions. This approach requires highly skilled anesthetic management to appropriately balance anesthetic depth and spontaneous respiration.\u003c/p\u003e \u003cp\u003eDuring rigid bronchoscopy, the airway remains open, complicating the measurement of ETCO₂. Consequently, pulse oxygenation (SpO₂) often serves as the only available parameter to evaluate ventilation. We previously reported on the feasibility and safety of transcutaneous CO₂ (TcCO\u003csub\u003e2\u003c/sub\u003e) monitoring during bronchoscopic interventions\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. In the current study, we hypothesized that TcCO₂ monitoring could provide a reliable method for assessing ventilation status during therapeutic bronchoscopic procedures. Therefore, the aim of this study was to evaluate the utility and safety of TcCO₂ measurements as a surrogate for partial pressure CO\u003csub\u003e2\u003c/sub\u003e (PaCO₂) and as an assessment tool for ventilation dynamics during therapeutic bronchoscopic interventions.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatient Characteristics and Interventions\u003c/h2\u003e \u003cp\u003eInitially, 42 patients were recruited for this study; however, 12 patients were subsequently excluded, leaving 30 patients enrolled in the final analysis. Exclusion reasons included TcCO₂ measurement failure (n\u0026thinsp;=\u0026thinsp;8), loss of spontaneous breathing due to muscle relaxant administration (n\u0026thinsp;=\u0026thinsp;2), and initiation of the intervention before the start of TcCO₂ monitoring (n\u0026thinsp;=\u0026thinsp;2). Among measurement failures, three were caused by difficulty attaching the sensor due to auricular dryness, while five resulted from calibration issues \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePatient demographics and clinical characteristics, including sex, age, height, weight, BMI, underlying conditions, and procedures performed, are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The median age was 71 years (range: 33\u0026ndash;86 years), and 46.7% (n\u0026thinsp;=\u0026thinsp;14) were male. The mean BMI was 19.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 kg/m\u0026sup2;. Lung cancer was the most common underlying condition (n\u0026thinsp;=\u0026thinsp;16), followed by esophageal cancer (n\u0026thinsp;=\u0026thinsp;5), chronic obstructive pulmonary disease (COPD; n\u0026thinsp;=\u0026thinsp;5), and endobronchial tuberculosis (n\u0026thinsp;=\u0026thinsp;5). Other diagnoses included tracheoesophageal fistula (n\u0026thinsp;=\u0026thinsp;2), iatrogenic subglottic stenosis (n\u0026thinsp;=\u0026thinsp;2), tracheal polyp (n\u0026thinsp;=\u0026thinsp;1), and malignant mediastinal tumour (n\u0026thinsp;=\u0026thinsp;1). Several patients presented with multiple overlapping diagnoses.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePatient demographics, underlying diseases, and procedures performed\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePatient Characteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years), Median (range)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e71 (33\u0026ndash;86)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex, n (%), Male / Female\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14 (46.7) / 16 (53.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI (kg/m\u0026sup2;), Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eUnderlying Diseases, n\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLung cancer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEsophageal cancer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTracheoesophageal fistula\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEndobronchial tuberculosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIatrogenic subglottic stenosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOPD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTracheal polyp\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMalignant mediastinal tumor\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eProcedures Performed, n\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAirway stent placement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eArgon plasma coagulation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBalloon dilation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStent removal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTumor resection\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eAbbreviations: BMI, body mass index; COPD, chronic obstructive pulmonary disease;\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eSD, standard deviation.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe most frequently performed procedure was airway stent placement (n\u0026thinsp;=\u0026thinsp;16), followed by APC (n\u0026thinsp;=\u0026thinsp;7), stent removal (n\u0026thinsp;=\u0026thinsp;6), balloon dilation (n\u0026thinsp;=\u0026thinsp;5), and tumour resection (n\u0026thinsp;=\u0026thinsp;4). Some patients underwent multiple procedures. Supplementary Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e provides detailed individual patient data.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eChanges in PaCO₂ and TcCO₂ during Intervention\u003c/h3\u003e\n\u003cp\u003eThe trends and statistical results of PaCO₂ and TcCO₂ are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Mean PaCO₂ values were 54.30\u0026thinsp;\u0026plusmn;\u0026thinsp;12.50 Torr at 7.5 minutes, 56.70\u0026thinsp;\u0026plusmn;\u0026thinsp;15.10 Torr at 15 minutes, and 63.20\u0026thinsp;\u0026plusmn;\u0026thinsp;21.10 Torr at 35 minutes after initiation of the intervention, showing a gradual increase over time. In contrast, mean TcCO₂ values were 53.92\u0026thinsp;\u0026plusmn;\u0026thinsp;13.19 Torr at 7.5 minutes, peaked at 60.13\u0026thinsp;\u0026plusmn;\u0026thinsp;14.93 Torr at 15 minutes, and then slightly decreased to 57.97\u0026thinsp;\u0026plusmn;\u0026thinsp;18.88 Torr at 35 minutes \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e Overall, both PaCO₂ and TcCO₂ remained elevated throughout the procedure.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTemporal changes and descriptive statistics of PaCO₂ and TcCO₂ measurements.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTime\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.5\u0026ndash;35 min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.5 min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15 min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e35 min\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePaCO₂, Torr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e57.21\u0026thinsp;\u0026plusmn;\u0026thinsp;16.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e54.30\u0026thinsp;\u0026plusmn;\u0026thinsp;12.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e56.70\u0026thinsp;\u0026plusmn;\u0026thinsp;15.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e63.20\u0026thinsp;\u0026plusmn;\u0026thinsp;21.10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e55.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e54.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e56.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e59.65\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMax\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e118.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e90.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e118.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRange\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e88.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e68.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e76.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTcCO₂, Torr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e57.57\u0026thinsp;\u0026plusmn;\u0026thinsp;15.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e53.92\u0026thinsp;\u0026plusmn;\u0026thinsp;13.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e60.13\u0026thinsp;\u0026plusmn;\u0026thinsp;14.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e57.97\u0026thinsp;\u0026plusmn;\u0026thinsp;18.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e53.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e59.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMax\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e118.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e80.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e87.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e118.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e28.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRange\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e90.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e52.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e87.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eAbbreviations: Min, minutes; PaCO₂, partial pressure of carbon dioxide; SD, standard deviation; TcCO₂, transcutaneous carbon dioxide.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eCorrelation Analysis of Gas Monitoring Parameters\u003c/h3\u003e\n\u003cp\u003eStrong correlations were observed between PaCO₂ and TcCO₂, as well as between SaO₂ and SpO₂ at each measured time point and throughout the overall monitoring period. Spearman's rank correlation coefficients (ρ) between PaCO₂ and TcCO\u003csub\u003e2\u003c/sub\u003e were 0.87 at 7.5 minutes, 0.89 at 15 minutes, 0.86 at 35 minutes, and 0.88 overall (7.5\u0026ndash;35 minutes) \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Similarly, correlation coefficients between SaO₂ and SpO\u003csub\u003e2\u003c/sub\u003e were 0.82 at 7.5 minutes, 0.84 at 15 minutes, 0.81 at 35 minutes, and 0.83 overall (7.5\u0026ndash;35 minutes) \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e All correlations were statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eAgreement Analysis of Monitoring Parameters\u003c/h3\u003e\n\u003cp\u003eBland-Altman analysis demonstrated good agreement between both PaCO₂ and TcCO₂, as well as SaO₂ and SpO₂ across all measured time points. For PaCO₂ and TcCO₂, the mean differences were\u003c/p\u003e \u003cp\u003e-0.95 mmHg at 7.5 minutes (limits of agreement: -21.76 to 19.86 mmHg), -1.22 mmHg at 15 minutes (-21.81 to 19.37 mmHg), and 5.24 mmHg at 35 minutes (-30.38 to 40.86 mmHg). When combining all time points (7.5\u0026ndash;35 minutes), the mean difference was 0.05 mmHg (-29.96 to 30.06 mmHg), indicating consistent agreement across the dataset \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFor SaO₂ and SpO₂, the mean differences were \u0026minus;\u0026thinsp;0.45% at 7.5 minutes (-7.99 to 7.10%), 0.17% at 15 minutes (-5.65 to 5.99%), and 0.11% at 35 minutes (-4.20 to 4.42%). The overall mean difference for all time points was \u0026minus;\u0026thinsp;0.09% (-6.76 to 6.58%), confirming high concordance throughout the procedure \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study demonstrated that TcCO₂ is an effective surrogate for PaCO₂ monitoring during rigid bronchoscopic interventions. While previous publications have been limited to case reports\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e, this study contributes prospective evidence supporting the utility of TcCO₂. Strong correlations were observed between PaCO₂ and TcCO₂ at all measured time points, and SpO₂ also showed high concordance with SaO₂. These findings suggest that TcCO₂ might be a reliable alternative for ventilation monitoring in clinical situations where ETCO₂ measurement is impractical.\u003c/p\u003e \u003cp\u003eIn prior studies of rigid bronchoscopy in paediatric populations, PaCO₂ levels were frequently elevated, with higher intraprocedural CO\u003csub\u003e2\u003c/sub\u003e levels associated with delayed ICU discharge\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. In our study, similarly high PaCO\u003csub\u003e2\u003c/sub\u003e and TcCO\u003csub\u003e2\u003c/sub\u003e values were observed (maximum: 118.4 Torr for both). Despite these elevations, all patients were successfully weaned from the ICU on the following day. Although the sample size was limited and no complications were observed, these findings suggest that continuous TcCO₂ monitoring may support early identification and prevention of CO\u003csub\u003e2\u003c/sub\u003e-related complications.\u003c/p\u003e \u003cp\u003ePrevious reports have evaluated ETCO\u003csub\u003e2\u003c/sub\u003e monitoring during adult rigid bronchoscopy under high-frequency jet ventilation (HFJV) \u003csup\u003e\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. However, ETCO\u003csub\u003e2\u003c/sub\u003e measurement under HFJV often requires brief pauses or reduced respiratory rates, leading to transient hypoventilation. Our findings suggest that for procedures performed with preserved spontaneous respiration, TcCO₂ provides valuable real-time information on ventilatory status and may enhance procedural safety.\u003c/p\u003e \u003cp\u003eAlthough ETCO₂ and PaCO₂ have been shown to correlate in patients with COPD, ETCO₂ generally underestimates PaCO₂, often resulting in clinically relevant discrepancies\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. In this study, five of 30 patients had COPD, but no discrepancies were observed between TcCO\u003csub\u003e2\u003c/sub\u003e and PaCO\u003csub\u003e2\u003c/sub\u003e. These findings indicate that TcCO\u003csub\u003e2\u003c/sub\u003e is a useful tool for CO\u003csub\u003e2\u003c/sub\u003e monitoring not only in rigid bronchoscopy but potentially in other procedures involving COPD patients.\u003c/p\u003e \u003cp\u003eThe Sentec Digital Monitoring System, used in this study has shown strong agreement with PaCO₂ in prior research\u003csup\u003e\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Its stable sensor attachment and rapid response characteristics make it particularly suited for intraoperative use \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Although rare issues with calibration and auricular attachment occurred, the sensor was generally well-tolerated.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eThis study has several limitations. The sample size was relatively small, which may limit the generalizability of the findings. Second, the duration of most procedures was short, reducing the ability to assess TcCO₂ performance during prolonged interventions. Third, while TcCO₂ and PaCO₂ showed strong agreement, the potential influence of peripheral perfusion and sensor placement variability was not fully explored. Future studies should evaluate TcCO₂ monitoring in longer procedures, in patients with unstable circulatory status, and in critically ill populations. Additional research is also needed to assess its impact on clinical outcomes and decision-making.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eTcCO₂ monitoring showed good agreement with PaCO₂ and may offer a practical, non-invasive method for assessing ventilation status during rigid bronchoscopy. These findings suggest that TcCO₂ could be a useful alternative in situations where ETCO₂ monitoring is not feasible.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design\u003c/h2\u003e \u003cp\u003eThis prospective observational study was conducted between June 2024 and January 2025 at St. Marianna University. Patients underwent therapeutic bronchoscopy procedures including airway stent placement, APC, balloon dilation, stent removal, and tumour resection. This study is in accordance with the ethical principles outlined of the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of St. Marianna University School of Medicine (HREC No. 6482). All participants provided informed written consent, including consent for publication, regarding all interventions.\u003c/p\u003e \u003cp\u003e \u003cem\u003eMonitoring and Procedure\u003c/em\u003es\u003c/p\u003e \u003cp\u003eThe Sentec Digital Monitoring System (TOKIBO Co., Ltd., Tokyo, Japan) was employed for TcCO₂ monitoring. Patients were positioned in the supine position, and a sensor was attached to the auricle to begin recording. An anaesthesiologist placed a radial arterial line (A-line) for continuous blood pressure monitoring and arterial blood gas sampling.\u003c/p\u003e \u003cp\u003eArterial blood samples were collected at 7.5, 15 and 35 minutes after initiation of the intervention. A rigid bronchoscope (EFRE-Dumon, EFER Medical, La Ciotat, France) was intubated in cases of central airway obstruction. All patients received intravenous anaesthesia with propofol and remifentanil.\u003c/p\u003e \u003cp\u003eBaseline Monitoring and Data Collection\u003c/p\u003e \u003cp\u003eThe time of rigid bronchoscope insertion past the vocal cords was defined as the starting point for physiological monitoring, and monitoring continued until the procedure concluded. Recorded parameters included TcCO₂, PaCO₂, SpO₂, PaO₂ and SaO₂.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eDescriptive statistics, including mean and standard deviation (SD) were calculated for each parameter. Correlation coefficients between TcCO₂ and PaCO₂, and between SaO₂ and SpO₂ at each time point, were assessed using Spearman\u0026rsquo;s rank correlation. Agreement between TcCO₂ and PaCO₂, as well as between SaO₂ and SpO₂, was evaluated using Bland-Altman analysis. All\u003c/p\u003e \u003cp\u003estatistical analyses were performed using JMP software version 17 (SAS Institution, Cary, NC,\u003c/p\u003e \u003cp\u003eUSA).\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank Jason Tonge for the English language review of this manuscript.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eY. N. had full access to data presented and takes responsibility for the integrity and accuracy of data analysis. H. T., H. H., K. N., and Y. S. contributed to bronchoscopic examinations and interpretation of findings. Y. N., H. H., K. M., and M. M. contributed to scientific review and approved the final manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The datasets generated and analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003cstrong\u003e\u003cbr\u003e\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBhavani-Shankar, K., Moseley, H., Kumar, A. Y. \u0026amp; Delph, Y. Capnometry and anaesthesia. \u003cem\u003eCan. J. Anaesth.\u003c/em\u003e \u003cb\u003e39\u003c/b\u003e, 617\u0026ndash;632 (1992).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDutau, H., Vandemoortele, T. \u0026amp; Breen, D. P. Rigid bronchoscopy. \u003cem\u003eClin. Chest Med.\u003c/em\u003e \u003cb\u003e34\u003c/b\u003e, 427\u0026ndash;435 (2013).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkamoto, S. et al. Anesthesia for rigid bronchoscopy: The impact of muscle relaxants. \u003cem\u003eAnesth. Analg\u003c/em\u003e. \u003cb\u003e131\u003c/b\u003e, 893\u0026ndash;900 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShinozaki, Y. et al. A prospective observation study of the dynamic monitoring of transcutaneous arterial blood oxygen saturation and carbon dioxide during bronchoscopy. \u003cem\u003eRespir Res.\u003c/em\u003e \u003cb\u003e25\u003c/b\u003e, 74 (2024).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGaunt, A., Jaggar, S. I. \u0026amp; Morgan, C. End-tidal capnography in rigid bronchoscopy. \u003cem\u003eAnaesthesia\u003c/em\u003e \u003cb\u003e57\u003c/b\u003e, 1039\u0026ndash;1040 (2002).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBordini, M. et al. Transcutaneous carbon dioxide monitoring in children undergoing rigid bronchoscopy: a prospective blinded observational study. \u003cem\u003eCan. J. Anaesth.\u003c/em\u003e \u003cb\u003e72\u003c/b\u003e, 273\u0026ndash;284 (2025).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFrietsch, T., Krafft, P., Becker, H. D., Buelzebruck, H. \u0026amp; Wiedemann, K. Intermittent capnography during high-frequency jet ventilation for prolonged rigid bronchoscopy. \u003cem\u003eActa Anaesthesiol. Scand.\u003c/em\u003e \u003cb\u003e44\u003c/b\u003e, 391\u0026ndash;397 (2000).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChhajed, P. N. et al. Measurement of combined oximetry and cutaneous capnography during flexible bronchoscopy. \u003cem\u003eEur. Respir J.\u003c/em\u003e \u003cb\u003e28\u003c/b\u003e, 386\u0026ndash;390 (2006).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSimon, M. et al. Comparison of transcutaneous and end-tidal CO₂-monitoring for rigid bronchoscopy during high-frequency jet ventilation. \u003cem\u003eActa Anaesthesiol. Scand.\u003c/em\u003e \u003cb\u003e47\u003c/b\u003e, 861\u0026ndash;867 (2003).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTyagi, D., Govindagoudar, M. B., Jakka, S., Chandra, S. \u0026amp; Chaudhry, D. Correlation of PaCO₂ and ETCO₂ in COPD patients with exacerbation on mechanical ventilation. \u003cem\u003eIndian J. Crit. Care Med.\u003c/em\u003e \u003cb\u003e25\u003c/b\u003e, 305\u0026ndash;309 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLermuzeaux, M. et al. Superiority of transcutaneous CO₂ over end-tidal CO₂ measurement for monitoring respiratory failure in nonintubated patients: A pilot study. \u003cem\u003eJ. Crit. Care\u003c/em\u003e. \u003cb\u003e31\u003c/b\u003e, 150\u0026ndash;156 (2016).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003evan Wijk, J. J., van Weteringen, W., Hoeks, S. E. \u0026amp; Staals, L. M. Validation of a new combined transcutaneous tcPCO₂ and tcPO₂ sensor in children in the operating theater. \u003cem\u003ePaediatr. Anaesth.\u003c/em\u003e \u003cb\u003e32\u003c/b\u003e, 429\u0026ndash;435 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUrbano, J. et al. Accuracy of three transcutaneous carbon dioxide monitors in critically ill children. \u003cem\u003ePediatr. Pulmonol.\u003c/em\u003e \u003cb\u003e45\u003c/b\u003e, 481\u0026ndash;486 (2010).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDomingo, C. et al. Optimal clinical time for reliable measurement of transcutaneous CO₂ with ear probes: counterbalancing overshoot and the vasodilatation effect. \u003cem\u003eSens. (Basel)\u003c/em\u003e. \u003cb\u003e10\u003c/b\u003e, 491\u0026ndash;500 (2010).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"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":"Arterial carbon dioxide (PaCO₂), rigid bronchoscopy, SpO₂, transcutaneous carbon dioxide (TcCO₂), ventilation monitoring","lastPublishedDoi":"10.21203/rs.3.rs-6547703/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6547703/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eEnd-tidal carbon dioxide (ETCO₂) monitoring is limited during rigid bronchoscopic procedures due to open airway conditions. This study aimed to evaluate the utility and safety of transcutaneous carbon dioxide (TcCO₂) monitoring as a surrogate for arterial CO₂ (PaCO₂) during therapeutic bronchoscopy.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eIn this prospective observational study, adult patients undergoing rigid bronchoscopy between June 2024 and January 2025 were enrolled. TcCO₂ was continuously monitored using the Sentec Digital Monitoring System. Arterial blood gas samples were collected at 7.5, 15, and 35 minutes after intervention initiation. Spearman\u0026rsquo;s rank correlation and Bland-Altman analyses were used to assess agreement between TcCO₂ and PaCO₂, and between SpO₂ and SaO₂.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThirty patients were analysed. Mean PaCO₂ increased over time, while TcCO₂ peaked at 15 minutes. Strong correlations were observed between PaCO₂ and TcCO₂ (ρ\u0026thinsp;=\u0026thinsp;0.86\u0026ndash;0.89, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and between SaO₂ and SpO₂ (ρ\u0026thinsp;=\u0026thinsp;0.81\u0026ndash;0.84, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Bland-Altman analysis confirmed good agreement at all time points for both gas exchange pairs.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eTcCO₂ monitoring is a reliable, non-invasive alternative to PaCO₂ measurement during rigid bronchoscopy. It provides real-time ventilation assessment in settings where ETCO₂ monitoring is not feasible, supporting its clinical integration.\u003c/p\u003e","manuscriptTitle":"Evaluation of the usefulness and safety of percutaneous CO2 monitoring during bronchoscopic intervention","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 05:55:25","doi":"10.21203/rs.3.rs-6547703/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-02-19T14:22:53+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-29T17:10:10+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-26T04:57:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"271782142187003866232321984824872219761","date":"2026-01-12T05:38:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"190491917525659156903006620500861132423","date":"2026-01-08T22:53:16+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-07T05:30:54+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-08T11:44:59+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-05-14T09:55:19+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-14T08:50:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-04-28T12:01:51+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":"9f16acfc-7580-42b1-acc2-79fdb5b57633","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":60811617,"name":"Health sciences/Medical research"},{"id":60811618,"name":"Health sciences/Medical research/Study design"}],"tags":[],"updatedAt":"2026-04-28T11:53:05+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-12 05:55:25","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6547703","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6547703","identity":"rs-6547703","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}