Physiological Impact of N95 Masks on Obese Operating Room Staff: A Randomized Crossover Trial

Physiological Impact of N95 Masks on Obese Operating Room Staff: A Randomized Crossover Trial | 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 Research Article Physiological Impact of N95 Masks on Obese Operating Room Staff: A Randomized Crossover Trial 川宇 犬牙, 燕哲 钡, 袁磊 高, 余 刘, 绍中 杨 This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4006747/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Obesity and mask both may increase the cardiopulmonary burden on medical staff. The physiological impact of surgical masks (SMs) and N95 masks on obese operating room staff remains uncertain. This study aimed to determine whether wearing N95 masks for 4 hours significantly affected physiological indices in obese medical staff compared to surgical masks (SMs). Methods In this randomized controlled two-phase crossover trial, the physiological impacts of wearing SMs and N95 masks for 4 hours was analysed among 20 obese operating room staff. The primary outcome was the change in venous carbon dioxide partial pressure (PvCO 2 ) levels at 4-hour intervention. Secondary outcomes included venous oxygen pressure (PvO 2 ), bicarbonate (HCO 3 − ) and pH levels at 4-hour intervention, end-tidal carbon dioxide partial pressure (PetCO 2 ), peripheral oxygen saturation (SpO 2 ), respiratory rate (RR), pulse rate (PR) and blood pressure (BP) at immediately, 1 h, 2 h, 3 h, and 4 h after mask wear. Dyspnoea, palpitations, headache were assessed with the visual analogue scale (VAS) score. Linear mixed models were used for comparative analysis. Results Twenty participants (age 32.2 [6.0] years; BMI 32.8 [2.1] kg/m 2 ; 45% female) completed the study. Compared with the no-mask condition, both SM and N95 masks wearing for 4 hours caused PvCO 2 , HCO 3 − , PetCO 2 , and RR levels increased slightly in obese operating room staff. N95 masks had a statistically significant rather than clinically significant impact on PvCO 2 (mean [95% CI], 1.4 [0.8, 1.9], P < 0.001) and RR (0.6 [0.1, 1.1)], P = 0.023) compared with SM. There was no significant difference between the two types of masks in terms of PvO 2 , pH, SpO 2 , PR, and BP. The three subjective VAS scores gradually increased over wear time. After more than 2 hours, the N95 group showed significantly increased than SM group. Conclusion Obese operating room staff continuously wearing SM or N95 masks 4 hours showed almost no difference in physiological impacts. It is recommended to wear N95 masks under high-risk conditions for better protection. Clinical trial registration : NCT05950256. obesity surgical mask N95 mask venous carbon dioxide partial pressure end-tidal carbon dioxide partial pressure physiological impacts Figures Figure 1 Figure 2 Figure 3 Introduction Obesity was identified as body mass index (BMI) of 30 kg/m 2 or higher according to the World Health Organization criteria [ 1 ]. In recent years, obesity has become a serious public health threat because of its rising prevalence [ 1 , 2 ]. Due to the accumulation of adipose tissue in the abdomen and chest, obesity can cause expiratory flow limited, atelectasis, and possibly hypoxemia and hypercapnia.[ 3 ] Medical staff are more prone to obesity due to factors such as long working hours, shift schedules, changes in body regulation, metabolism, and stress [ 4 , 5 ]. To prevent surgical site infections in patients and protect medical staff from contaminated blood, body fluids, and most surgical smoke [ 6 , 7 ], operating room staff are required to wear masks according to established guidelines and it is recommended to replace masks every 4 hours [ 8 ]. However, it is not clear if wear masks affect respiratory function and comfort experience in obese medical staff. Wearing masks by medical staff has been proven to be associated with various symptoms, including hypoxemia, physiological changes, as well as subjective discomfort such as breathing difficulties and headaches [ 9 , 10 ]. Early studies had found that surgical mask (SM) can reduce postoperative peripheral oxygen saturation (SpO 2 ) and increase pulse rate (PR) for surgeons compared to preoperative conditions [ 11 ]. Our previous research revealed a significantly reduced SpO 2 and increased respiratory rate (RR) in anaesthesiologists wearing SMs for more than 2 hours [ 12 ]. N95 masks exhibited better protective properties and particularly suitable for high-risk environments compared with SMs [ 13 , 14 ]. Notably, researches showed that N95 masks significantly increased end-tidal carbon dioxide pressure (PetCO 2 ) of intensive care unit (ICU) nurses after wearing for 12 hours [ 15 ]. In addition, medical staff within emergency departments wearing N95 masks for 4 hours caused changes in gas exchange, including plasma pH, venous oxygen pressure (PvO 2 ) decreased and PetCO 2 increased [ 16 ]. Both obesity and masks may contribute to increase the cardiopulmonary burden, but there is no evidence to show whether these two types of masks have a negative effect on the respiratory function of obese medical staff. Therefore, this study aims to compare the effects of wearing SM or N95 masks for 4 hours on physiological indices among obese operating room medical staff. This can help medical staff to formulate strategies on optimizing medical protection. Methods Ethics approval This single-centre, prospective, randomized crossover trial was conducted in the operating room of Qilu Hospital, Shandong University, China, from July 2023 to October 2023. The study was approved by the Qilu Hospital of Shandong University Medical Ethics Committee (No. KYLL-202306-032) and registered before patient enrollment at ClinicalTrials.gov (NCT05950256, principal investigator: Shaozhong Yang, date of registration: July 10, 2023). Written informed consent was obtained from all participants. Study followed the Consolidated Standards of Reporting Trials (CONSORT) guideline (Fig. 1 ). Participants We recruited 20 obese participants aged 20–60 years, nonsmoking, with a body mass index (BMI) ≥ 30kg/m 2 , and without chronic diseases from anaesthesiologists and nurses in the operating room. Regardless of sex, they voluntarily participated in this study. The exclusion criteria were recent acute or chronic respiratory disease; recent history of headache or dizziness; pregnancy or lactation; rhinitis; nasal polyps; respiratory distress; facial skin inflammation; or skin laxity. Each participant provided written informed consent before participating in this study. Randomization An allocation and randomization list was generated by a computer program. Participants were randomly assigned to either SM-first group or N95 mask-first group in a 1:1 ratio, and completed data observation during the continuous wearing of SMs or N95 masks for 4 hours. Trial outcomes adjudicators and statisticians were blinded to group allocation (study flowchart, Fig. 1 ). After a 24-hour washout period, the protocol was repeated. Intervention and Protocol To avoid using daily personal protective equipment familiar to participants, N95 masks and SMs were purchased from third-party suppliers outside Qilu Hospital of Shandong University and did not undergo compatibility testing. During the study period, each participant was required to correctly wear a disposable lace-up SM (Dongbei Medical Strap Style, China) or a disposable N95 mask (Dongbei Medical NST-9502, China). Participants were required to avoid using masks for at least 10 minutes before the test started and to stay away from the clinical area to ensure that baseline measurements were obtained under normal breathing conditions. The subjects were seated and connected to a nasal sampling tube using a Micro Sideflow End expiratory Carbon Dioxide Monitor (Capnosteam20p, Medtronic, Boulder, Co.). The right index finger was connected to a pulse oximetry probe, while an electronic sphygmomanometer (Omron U724J, China, Omron Co., Ltd.) was used to measure blood pressure (BP). Baseline data (T0) were collected without the participant wearing a mask, and the participants were blinded to the monitoring and BP readings. Then, the participants were asked to use a nasal sampling tube and wear an SM or N95 mask continuously for 4 hours during medical work. To ensure the airtightness of the mask, a sterile wound dressing was used to fix the sampling tube between the mask and skin, and the patient underwent a mask facial leakage test (eFigure 1). After the first stage and a 24-hour washout period, the second stage began. If participants were unable to persist, they can immediately remove the mask and abandon the test. Researchers monitored these subjects until symptoms improved. Data collection The baseline data included SpO 2 , the RR, the pulse rate (PR), PetCO 2 , BP, and subjective sensation scores for dyspnoea, palpitation and headache. Venous blood (1 ml) was collected from the participants, and baseline values for the no-mask condition were measured using a blood gas analyser (Cobas b 123, Roche Diagnostics). The pH, PvO 2 , venous carbon dioxide partial pressure (PvCO 2 ), and bicarbonate (HCO 3 − ) levels were recorded. To reduce harm to the subjects, baseline venous blood gas analysis was performed only once. Subsequently, the abovementioned data were collected using the same method immediately after mask wearing (T1) (after three regular breaths) and after continuous mask wearing for 1 hour (T2), 2 hours (T3), 3 hours (T4), and 4 hours (T5). To minimize data variability, data were collected twice at each time point, after which the average value was calculated. After continuously wearing an SM or N95 mask for 4 hours, 1 ml of venous blood was extracted for blood gas analysis. All subjective sensations were scored by means of a 10-point visual analogue scale (VAS) from 0 (no discomfort) to 10 (worst discomfort imaginable). Outcomes The primary outcome was the change in PvCO 2 value after continuous SM and N95 mask wearing for 4 hours. The secondary outcomes were PetCO 2 , SpO 2 , the PR, the RR, BP, and the VAS subjective sensation scores at 5 time points (T1, T2, T3, T4 and T5), as well as the pH, PvO 2 , and HCO 3 − of venous blood gas after 4 hours of mask wear. Sample size calculation The sample size was calculated with Pass 15 (NCSS, LLC, Kaysville, UT, USA). In our preliminary experiment, six obese anaesthesiologists working in the operating room were included; after 4 hours of the intervention, the difference in the PvCO 2 between the SM and N95 mask groups was 1.5 (1.3) mmHg. With a two-sided test, an α of 5%, and a power of 90%, 18 participants were needed. Assuming a 10% dropout rate, we included a total of 20 participants. Statistical analysis Statistical analysis was performed using R software (version 4.3.1). Categorical data are represented as numbers or percentages. Continuous data were tested for normality using the Shapiro-Wilk test and are expressed as the mean (standard deviation) or median (interquartile range [IQR]). A linear mixed model (eSupplementary 1) was established the differences in physiological changes caused by N95 masks and SMs, as well as the differences in physiological changes caused by different intervention measures within subjects over time, while considering the internal correlations among subjects caused by cross design and repeated measurements. We modeled the cyclical and carryover effects, and used the FDR method for correction after multiple comparisons. A P value of < 0.05 was considered to indicate statistical significance. Results Between July 2023 and October 2023, among 199 operating room medical staff, 33 obese medical staff were assessed for eligibility. As described in the flowchart (Fig. 1 ), 13 participants were excluded, and ultimately 20 obese participants were randomized. Basic characteristics Twenty obese participants in the operating room (mean [SD] age, 32.2 [6.0] years; 9 women [45%]) completed this study, with an average BMI of 32.8 (SD, 2.1) kg/m 2 . There were no significant differences in baseline values for age, height, weight, BMI, venous blood gas or physiological indicators between the SM-first group and the N95 mask-first group (Table 1 ). Table 1 Baseline characteristics of the participants. Characteristics Total participants SM-first group N95 mask-first group P value No. (%) of participants (n = 20) 20 (100) 10 (50) 10 (50) Sex Female (%) 9 (45) 4 (40) 5 (50) Male (%) 11 (55) 6 (60) 5 (50) Age, years 32.2 (6.0) 31.2 (4.6) 33.2 (7.2) 0.467 Height, cm 168.6 (6.1) 169.9 (7.1) 167.4 (5.1) 0.377 Weight, kg 93.8 (11.7) 95.9 (13.6) 91.6 (9.6) 0.425 BMI, kg/m 2 32.8 (2.1) 33.0 (2.4) 32.6 (1.8) 0.701 PvCO 2 (mmHg) 47.1 (4.1) 46.9 (5.3) 47.3 (2.8) 0.811 pH 7.353 (0.037) 7.356 (0.046) 7.350 (0.026) 0.752 PvO 2 (mmHg) 39.0 (3.9) 38.8 (4.3) 39.1 (3.6) 0.863 HCO 3 − (mmol/L) 25.2 (1.0) 25.2 (1.1) 25.2 (0.8) 0.928 PetCO 2 (mmHg) 37.4 (2.7) 37.4 (3.2) 37.5 (2.1) 0.904 SpO 2 (%) 97.1 (1.0) 97.0 (0.7) 97.2 (1.2) 0.575 RR (breaths/min) 17.1 (2.7) 16.4 (2.8) 17.9 (2.4) 0.220 PR (beats/min) 83.4 (12.7) 81.8 (9.4) 85. 0 (15.6) 0.582 SBP (mmHg) 119.3 (10.2) 121.8 (10.8) 116. 8 (9.4) 0.283 DBP (mmHg) 76.7 (7.4) 77.9 (8.4) 75.5 (6.4) 0.483 Values are presented as the mean (SD) and number of patients (%). Abbreviations: BMI, body mass index; SM, surgical mask; PvCO 2 , venous carbon dioxide partial pressure (PvCO 2 ); HCO 3 − , bicarbonate; PvO 2 , venous oxygen pressure; PetCO 2 , partial pressure of end-tidal carbon dioxide; SpO 2 , peripheral blood oxygen saturation; RR, respiratory rate; PR, pulse rate; SBP, systolic blood pressure; DBP, diastolic blood pressure. Differences between the SM-first group and the N95 mask-first group were tested by independent-sample t test. Primary Outcome Measure Estimates of mean changes between baseline and 4 hours of mask intervention obtained from the repeated measures analysis are reported in Table 2 . There was a significant difference in the primary outcome measure ( P < 0.001), changes in average PvCO 2 , between N95 masks (3.3 [2.2, 4.4]) and SM (1.9 ([0.9, 3.00]). Compared to continuously wearing SMs 4 hours, N95 mask wear for 4 hours significantly increased PvCO 2 [49.0 (3.8) vs. 50.4 (4.0), P < 0.001] (Table 2 ). Baseline venous blood gas was only collected once in both groups. As shown in Fig. 2 , the PvCO 2 values of the N95 mask group were significantly higher in both stage 1(Mean [95% CI], 1.6 [0.9, 2.3], P < 0.001) and stage 2 (Mean [95% CI], 1.1 [0.0, 2.2], P = 0.044 ), indicating that the N95 mask had a more significant treatment effect (eTable 2). Table 2 Estimated mean changes of all outcome measures between baseline and 4 hours. Outcome Estimated change between baseline and 4 h, mean (95% CI) SM group N95 mask group SM vs N95 group P value PvCO 2 (mmHg) 1.9 (0.9, 3.0) 3.3 (2.2, 4.4) 1.4 (0.8, 1.9) < 0.001 pH -0.008 (-0.023, 0.008) -0.016 (-0.031, 0) -0.008 (-0.016, 0.001) 0.078 PvO 2 (mmHg) -1.3 (-2.3, -0.2) -1.3 (-2.4, -0.3) -0.1 (-0.5, 0.4) 0.822 HCO 3 − (mmol/L) 0.6 (0, 1.1) 0.8 (0.3, 1.4) 0.2 (-0.1, 0.6) 0.229 PetCO 2 (mmHg) 3.2 (2.3, 4.1) 3.3 (2.4, 4.1) 0 (-0.3, 0.4) 0.886 SpO 2 (%) -0.3 (-0.7, 0.1) 0 (-0.4, 0.4) 0.3 (-0.1, 0.7) 0.180 RR (breaths/min) 1.2 (0.6, 1.8) 1.8 (1.2, 2.4) 0.6 (0.1, 1.1) 0.023 PR (beats/min) -1.9 (-4.8, 1.1) -1.6 (-4.6, 1.3) 0.3 (-2.2, 2.7) 0.840 SBP (mmHg) -1.1 (-4.4, 2.3) -0.2 (-3.5, 3.1) 0.9 (-3.1, 4.8) 0.676 DBP (mmHg) -1.3 (-5.2, 2.6) 0.7 (-3.2, 4.5) 2 (-2.6, 6.5) 0.400 VAS of Dyspnea 1.8 (1.4, 2.1) 2.9 (2.5, 3.2) 1.1 (0.8, 1.4) < 0.001 VAS of Headache 1.9 (1.6, 2.2) 2.9 (2.6, 3.2) 1.0 (0.7, 1.3) < 0.001 VAS of Palpitation 1.4 (1.1, 1.6) 2.4 (2.1, 2.6) 1.0 (0.7, 1.3) < 0.001 The primary outcome was PvCO 2 . All other variables were secondary outcomes. Estimates were obtained using a repeated-measures modeling framework. Abbreviations: SM, surgical mask; CI, confidence interval; PvCO 2 , venous carbon dioxide partial pressure; HCO 3 − , bicarbonate; PvO 2 , venous oxygen pressure; PetCO 2 , partial pressure of end-tidal carbon dioxide; SpO 2 , peripheral blood oxygen saturation; RR, respiratory rate; PR, pulse rate; SBP, systolic blood pressure; DBP, diastolic blood pressure; VAS, visual analogue scale. Secondary Outcome Measures The treatment effect, period effect, and carryover effect of secondary outcome measures in crossover study were validated (eTable 2). Estimates of mean changes between baseline and 4 hours for secondary outcome measures are presented in Table 2 . After continuous masks wearing for 4 hours, there was no significant difference in the changes in venous blood gas pH, PvO 2 , HCO 3 − , and physiological indices such as PetCO 2 , RR, PR, SpO 2 , and BP between the two groups. The pH, PvO 2 , HCO 3 − changes between the two groups in stage 1 and stage 2 were also not significant (Fig. 2 ). As shown in Fig. 3 and eTable 3, at each time point, intergroup comparisons were made between SM and N95 mask interventions, and the results showed that there were no significant differences in PetCO 2 , RR, SpO 2 , SBP, and DBP. Both groups showed a significant increase in PetCO 2 ( P < 0.001) immediately after donning an SM or N95 mask (T1). After continuous wearing of masks for 4 hours (T5), the estimated mean change in PR between baseline and N95 mask group was significantly increased than that of the SM group (Mean [95% CI], 0.6 [0.1, 1.1], P = 0.023). At each time point, the mean estimated changes in VAS scores for dyspnoea, headache and palpitations were compared between the N95 mask and SM groups at baseline and that time point (Fig. 4). With prolonged SM and N95 mask wear, the VAS scores of the obese operating room staff for dyspnoea, palpitations and headache gradually increased. Intergroup comparisons revealed significant differences ( P < 0.001) in the VAS scores for the three subjective sensations between the two mask interventions at 2, 3, and 4 hours (Table 2 and Fig. 4). With increasing mask use duration, the subjective VAS scores of participants in the N95 mask group increased more significantly than did those of participants in the SM group, but the scores remained tolerable (mean VAS score, < 3). Discussion Obesity and mask use may both increase the cardiopulmonary burden [ 3 , 12 – 14 ]. This study investigated the physiological effects of SM and N95 mask wearing on obese operating room staff through self-comparison. This crossover trial showed that continuous SM or N95 masks wearing for 4 hours significantly increased PvCO2, PetCO 2 , and RR in obese operating room staff. Compared with SM, N95 masks wearing had a more significant effect on PvCO 2 , but there was no significant difference in other venous blood gas and physiological indices between the two types of masks. Combined with the venous blood indices, these changes are unlikely to have clinical significance. We also observed a significant increase in the PetCO 2 immediately after SM and N95 mask wearing compared to no mask wearing. This change may be related to psychological factors, and the increase in the RR may be a compensatory mechanism for the increase in PetCO 2 [ 17 ]. After continuous mask wearing for 2 hour, the subjective VAS scores of obese participants in the N95 mask group were significantly greater than those in the SM group; however, all of these scores were within a tolerable range. Indicating that the subjective discomfort of the two types of masks will not seriously affect obese medical staff in the operating room. The impact of SMs or N95 masks on healthy nonobese healthcare workers has been extensively confirmed [ 12 , 15 , 16 ]. A study of ICU medical staff confirmed that wearing N95 masks for prolonged work did not result in a significant decrease in SpO 2 or a significant increase in heart rate [ 18 ]. These research results are basically consistent with our research data, indicating that it is safe for obese health care workers without a history of cardiopulmonary disease to use masks for extended periods during daily medical activities. However, studies on the impact of masks on obese people are rare. A study showed that obese children were more likely to experience respiratory distress while wearing masks. After walking tests, overweight or obese children showed a significant increase in PetCO 2 and in the PR and RR, but no significant changes in SpO 2 were observed [ 19 ]. Consistent with our research findings, they also observed a significant increase in PetCO 2 when obese children used masks immediately. In healthy individuals, N95 masks cause minimal changes in blood gas and other physiological parameters during physical activity, even during very intense exercise[ 20 ]. A recent study of healthy volunteers suggested that even with mild exercise, prolonged wear of N95 masks can increase respiratory resistance, leading to a decrease in RR and SpO 2 within 1 hour and an increase in heart rate after 2 hours until the mask is removed [ 21 ]. Consistent with our research findings, this study also did not find any changes in BP, as healthy individuals can compensate for this cardiovascular overload. Although our data support that SMs and N95 masks have a smaller impact on physiological indices, N95 masks have higher subjective sensation scores, which are related to tighter facial seals. After wearing N95 masks for 4 hours, the inhalation and exhalation resistance increased by 0.43 and 0.23 mmH 2 O, respectively. The average moisture retention in the mask is 0.26 ml [ 22 ]. Compared to no mask, N95 masks increase the temperature of inhaled air by 1.13 times during eight breaths and increase the CO 2 concentration by 7.3 times [ 23 ]. An increase in heat and humidity inside N95 masks directly leads to an increase in respiratory resistance, repeated CO 2 breathing, and an increase in subjective sensations such as dyspnoea. Based on the findings of our study, we believe that headaches are unlikely to be caused by physiological changes in the balance of O 2 and CO 2 and may be due to facial pain behind the ears or other contact points caused by mask straps.[ 9 ] Indirect factors, such as insufficient hydration and an irregular diet, may also lead to headaches when individuals wear masks for a long time [ 24 ]. Recent research data suggest that prolonged use of masks in medical environments has limited effects on the PR and HR of healthcare workers. Although the subjective perception score for palpitations significantly increases, more consideration should be given to psychological factors [ 9 , 25 ]. Masks are usually used to prevent respiratory virus infections, but their effectiveness may vary depending on the type of mask used. There is currently insufficient evidence supporting the use of medical masks or SMs to combat influenza or coronavirus infections, with N95 masks being the most effective [ 26 ]. Our research suggested that there was almost no difference in the impact of SMs or N95 masks on the physiological indicators of obese healthcare workers. These findings may help to persuade obese healthcare workers to wear N95 masks for better protection. Our research advantage lies in the monitoring of obese medical staff during daily medical work in the operating room rather than during intense exercise or running, which has more practical significance for clinical guidance. This study has several limitations. First, venous blood was used for blood gas analysis to increase the comfort of the study participants. We were only observing the differences in several blood gas indicators in the mask group, not for therapeutic purposes. Second, due to the small sample size, sex and age subgroup analysis was not conducted. Third, we only observed participants for 4 hours and did not collect data on the safety of using masks for longer periods, as masks are disposable, and their protective effects weaken over time; it is generally recommended that masks be replaced every 4 hours [ 8 , 27 ]. Finally, to minimize interference with surgery, obese surgeons were not included in this study, which affected the generalizability of the results. Conclusions Obese operating room staff who participate in routine medical work can wear SMs or N95 masks for 4 hours without significantly increasing the risk of physiological burden. It is recommended that N95 masks be worn under high-risk conditions for better protection and replaced every 4 hours according to established guidelines. Future research should focus on the effects of masks on sex and age differences. Declarations Ethics approval and consent to participate The protocol was approved by the Qilu Hospital of Shandong University Medical Ethics Committee (No. KYLL-202306-032), and each participant provided written informed consent. All studies were carried out in accordance with the Declaration of Helsinki (2013 Edition). Consent for publication Not applicable. Availability of data and materials The datasets used in the present study are available from the corresponding author upon reasonable request. Declarations of interest The authors declare that they have no conflicts of interest. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Author contributions Data collection: CYF and YL Statistical analysis: YLG and YZB Writing of the manuscript: SZY and YL Inception of the study idea: SZY and CYF Study design: SZY and CYF Revision of the manuscript: SZY and YL All the authors approved the final manuscript. 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Phys Fluids (1994). 2021;33(8):081913. Ong JJY, Bharatendu C, Goh Y, Tang JZY, Sooi KWX, Tan YL, Tan BYQ, Teoh HL, Ong ST, Allen DM, et al. Headaches Associated With Personal Protective Equipment - A Cross-Sectional Study Among Frontline Healthcare Workers During COVID-19. Headache. 2020;60(5):864–77. Sheng Chew NW, Chiew Wong RC, Djohan AH, Ngiam JN, Chai P, Yeo TC, Tan HC, Sia CH. Association of face mask use with self-reported cardiovascular symptoms during the COVID-19 pandemic. Singap Med J. 2023;64(10):609–15. Kim MS, Seong D, Li H, Chung SK, Park Y, Lee M, Lee SW, Yon DK, Kim JH, Lee KH, et al. Comparative effectiveness of N95, surgical or medical, and non-medical facemasks in protection against respiratory virus infection: A systematic review and network meta-analysis. Rev Med Virol. 2022;32(5):e2336. Loveday HP, Wilson JA, Pratt RJ, Golsorkhi M, Tingle A, Bak A, Browne J, Prieto J, Wilcox M. Health UKDo: epic3: national evidence-based guidelines for preventing healthcare-associated infections in NHS hospitals in England. J Hosp Infect. 2014;86(Suppl 1):1–70. Additional Declarations No competing interests reported. Supplementary Files SupplementaryOnlineContent.docx Cite Share Download PDF Status: Posted Version 1 posted 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-4006747","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":276187949,"identity":"197d911a-3c3c-4eda-8ae1-735c107bca75","order_by":0,"name":"川宇 犬牙","email":"","orcid":"","institution":"Qilu Hospital of Shandong University","correspondingAuthor":false,"prefix":"","firstName":"川宇","middleName":"","lastName":"犬牙","suffix":""},{"id":276187955,"identity":"56ece7f8-8036-42c3-a689-a27c5d2d640b","order_by":1,"name":"燕哲 钡","email":"","orcid":"","institution":"Qilu Hospital of Shandong University","correspondingAuthor":false,"prefix":"","firstName":"燕哲","middleName":"","lastName":"钡","suffix":""},{"id":276187957,"identity":"216b551d-3942-402e-90dc-ce3d7bde9ba6","order_by":2,"name":"袁磊 高","email":"","orcid":"","institution":"Qilu Hospital of Shandong University","correspondingAuthor":false,"prefix":"","firstName":"袁磊","middleName":"","lastName":"高","suffix":""},{"id":276187959,"identity":"18621acf-c252-4bc8-9d91-b7bca877772e","order_by":3,"name":"余 刘","email":"","orcid":"","institution":"Qilu Hospital of Shandong University","correspondingAuthor":false,"prefix":"","firstName":"余","middleName":"","lastName":"刘","suffix":""},{"id":276187961,"identity":"1a86a441-9ff2-4772-a323-53229e1c9f5f","order_by":4,"name":"绍中 杨","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvUlEQVRIiWNgGAWjYBADOTb29gOkaTHm4zmTQJqWxHkSDgbEKTU4f/yZxM8dteltEgwJDD8qthGh5UZCmmTvmeO5bdKNBxh7ztwmRgvDMQnetmO5bTIHEpgZ24jRcv5gm+TftmPpbBIJBkRqOZDMJs3bVpNAvBbJG2nM1rJtBwzbgIF8kCi/8J0//vDm27Y6efn29oMPflQQoUXhAAOLBAPDYTDnAGH1QCDfwMD8gYGhjijFo2AUjIJRMEIBAIhkP1aPnpnMAAAAAElFTkSuQmCC","orcid":"","institution":"Qilu Hospital of Shandong University","correspondingAuthor":true,"prefix":"","firstName":"绍中","middleName":"","lastName":"杨","suffix":""}],"badges":[],"createdAt":"2024-03-02 15:05:02","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4006747/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4006747/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":52104422,"identity":"8359ca5a-7187-4b50-96e9-866ada30af26","added_by":"auto","created_at":"2024-03-06 19:25:05","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":213952,"visible":true,"origin":"","legend":"\u003cp\u003eStudy flowchart\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4006747/v1/07aeaf6a1e8e9a84c69432dc.jpg"},{"id":52104424,"identity":"a46f9697-9c56-4061-a8d0-03caf501ab7b","added_by":"auto","created_at":"2024-03-06 19:25:05","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":298164,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of reported PvCO\u003csub\u003e2\u003c/sub\u003e, PvO\u003csub\u003e2\u003c/sub\u003e, pH and HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e- \u003c/sup\u003eamong the two-stage SM and N95 mask wearing conditions.\u003c/p\u003e\n\u003cp\u003eAbbreviations: PvCO\u003csub\u003e2\u003c/sub\u003e, venous carbon dioxide partial pressure (PvCO\u003csub\u003e2\u003c/sub\u003e); HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e, bicarbonate; PvO\u003csub\u003e2\u003c/sub\u003e, venous oxygen pressure; IQR, interquartile range.\u003c/p\u003e\n\u003cp\u003eThe horizontal line in the middle of each box indicates the median, the top and bottom borders of the box mark the 75th and 25th percentiles, the whiskers above and bolow the box indicate the 75th percentile +1.5 IQR and 25th percentile -1.5 IQR, and the points beyond the whiskers are outliers.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4006747/v1/d4d101a284038157ffa3c24d.jpg"},{"id":52104423,"identity":"46faf90c-a35f-43b7-bb04-399e221fc8a0","added_by":"auto","created_at":"2024-03-06 19:25:05","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":388906,"visible":true,"origin":"","legend":"\u003cp\u003eEstimated mean changes in physiological indices and VAS scores for Subjective sensations during 4-hour intervention with SMs and N95 masks.\u003c/p\u003e\n\u003cp\u003eAbbreviations: SM, surgical mask; PetCO\u003csub\u003e2\u003c/sub\u003e, partial pressure of end-tidal carbon dioxide; SpO\u003csub\u003e2\u003c/sub\u003e, peripheral blood oxygen saturation; RR, respiratory rate; PR, pulse rate; SBP, systolic blood pressure; DBP, diastolic blood pressure; VAS, visual analogue scale.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e values (lower left corner of the column) indicate the group × time interaction effect.\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4006747/v1/6ab54127586ae79f3d53a510.jpg"},{"id":52173835,"identity":"6a2d24a3-86d2-4d23-8750-dd119990c49f","added_by":"auto","created_at":"2024-03-07 16:34:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":610088,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4006747/v1/513ba770-0201-45d6-bf41-1107c9204d73.pdf"},{"id":52105867,"identity":"c7b41454-c964-4cc2-8d79-d1afd50ab81b","added_by":"auto","created_at":"2024-03-06 19:33:05","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":506089,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryOnlineContent.docx","url":"https://assets-eu.researchsquare.com/files/rs-4006747/v1/cab3958aba5c0aeaad7ab16e.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Physiological Impact of N95 Masks on Obese Operating Room Staff: A Randomized Crossover Trial","fulltext":[{"header":"Introduction","content":"\u003cp\u003eObesity was identified as body mass index (BMI) of 30 kg/m\u003csup\u003e2\u003c/sup\u003e or higher according to the World Health Organization criteria [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In recent years, obesity has become a serious public health threat because of its rising prevalence [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Due to the accumulation of adipose tissue in the abdomen and chest, obesity can cause expiratory flow limited, atelectasis, and possibly hypoxemia and hypercapnia.[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] Medical staff are more prone to obesity due to factors such as long working hours, shift schedules, changes in body regulation, metabolism, and stress [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. To prevent surgical site infections in patients and protect medical staff from contaminated blood, body fluids, and most surgical smoke [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], operating room staff are required to wear masks according to established guidelines and it is recommended to replace masks every 4 hours [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, it is not clear if wear masks affect respiratory function and comfort experience in obese medical staff.\u003c/p\u003e \u003cp\u003eWearing masks by medical staff has been proven to be associated with various symptoms, including hypoxemia, physiological changes, as well as subjective discomfort such as breathing difficulties and headaches [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Early studies had found that surgical mask (SM) can reduce postoperative peripheral oxygen saturation (SpO\u003csub\u003e2\u003c/sub\u003e) and increase pulse rate (PR) for surgeons compared to preoperative conditions [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Our previous research revealed a significantly reduced SpO\u003csub\u003e2\u003c/sub\u003e and increased respiratory rate (RR) in anaesthesiologists wearing SMs for more than 2 hours [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eN95 masks exhibited better protective properties and particularly suitable for high-risk environments compared with SMs [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Notably, researches showed that N95 masks significantly increased end-tidal carbon dioxide pressure (PetCO\u003csub\u003e2\u003c/sub\u003e) of intensive care unit (ICU) nurses after wearing for 12 hours [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In addition, medical staff within emergency departments wearing N95 masks for 4 hours caused changes in gas exchange, including plasma pH, venous oxygen pressure (PvO\u003csub\u003e2\u003c/sub\u003e) decreased and PetCO\u003csub\u003e2\u003c/sub\u003e increased [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBoth obesity and masks may contribute to increase the cardiopulmonary burden, but there is no evidence to show whether these two types of masks have a negative effect on the respiratory function of obese medical staff. Therefore, this study aims to compare the effects of wearing SM or N95 masks for 4 hours on physiological indices among obese operating room medical staff. This can help medical staff to formulate strategies on optimizing medical protection.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e \u003cstrong\u003eEthics approval\u003c/strong\u003e \u003cp\u003eThis single-centre, prospective, randomized crossover trial was conducted in the operating room of Qilu Hospital, Shandong University, China, from July 2023 to October 2023. The study was approved by the Qilu Hospital of Shandong University Medical Ethics Committee (No. KYLL-202306-032) and registered before patient enrollment at ClinicalTrials.gov (NCT05950256, principal investigator: Shaozhong Yang, date of registration: July 10, 2023). Written informed consent was obtained from all participants. Study followed the Consolidated Standards of Reporting Trials (CONSORT) guideline (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003c/p\u003e\n\u003ch3\u003eParticipants\u003c/h3\u003e\n\u003cp\u003eWe recruited 20 obese participants aged 20\u0026ndash;60 years, nonsmoking, with a body mass index (BMI)\u0026thinsp;\u0026ge;\u0026thinsp;30kg/m\u003csup\u003e2\u003c/sup\u003e, and without chronic diseases from anaesthesiologists and nurses in the operating room. Regardless of sex, they voluntarily participated in this study. The exclusion criteria were recent acute or chronic respiratory disease; recent history of headache or dizziness; pregnancy or lactation; rhinitis; nasal polyps; respiratory distress; facial skin inflammation; or skin laxity. Each participant provided written informed consent before participating in this study.\u003c/p\u003e\n\u003ch3\u003eRandomization\u003c/h3\u003e\n\u003cp\u003eAn allocation and randomization list was generated by a computer program. Participants were randomly assigned to either SM-first group or N95 mask-first group in a 1:1 ratio, and completed data observation during the continuous wearing of SMs or N95 masks for 4 hours. Trial outcomes adjudicators and statisticians were blinded to group allocation (study flowchart, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). After a 24-hour washout period, the protocol was repeated.\u003c/p\u003e\n\u003ch3\u003eIntervention and Protocol\u003c/h3\u003e\n\u003cp\u003eTo avoid using daily personal protective equipment familiar to participants, N95 masks and SMs were purchased from third-party suppliers outside Qilu Hospital of Shandong University and did not undergo compatibility testing. During the study period, each participant was required to correctly wear a disposable lace-up SM (Dongbei Medical Strap Style, China) or a disposable N95 mask (Dongbei Medical NST-9502, China).\u003c/p\u003e \u003cp\u003eParticipants were required to avoid using masks for at least 10 minutes before the test started and to stay away from the clinical area to ensure that baseline measurements were obtained under normal breathing conditions. The subjects were seated and connected to a nasal sampling tube using a Micro Sideflow End expiratory Carbon Dioxide Monitor (Capnosteam20p, Medtronic, Boulder, Co.). The right index finger was connected to a pulse oximetry probe, while an electronic sphygmomanometer (Omron U724J, China, Omron Co., Ltd.) was used to measure blood pressure (BP). Baseline data (T0) were collected without the participant wearing a mask, and the participants were blinded to the monitoring and BP readings. Then, the participants were asked to use a nasal sampling tube and wear an SM or N95 mask continuously for 4 hours during medical work. To ensure the airtightness of the mask, a sterile wound dressing was used to fix the sampling tube between the mask and skin, and the patient underwent a mask facial leakage test (eFigure 1). After the first stage and a 24-hour washout period, the second stage began. If participants were unable to persist, they can immediately remove the mask and abandon the test. Researchers monitored these subjects until symptoms improved.\u003c/p\u003e\n\u003ch3\u003eData collection\u003c/h3\u003e\n\u003cp\u003eThe baseline data included SpO\u003csub\u003e2\u003c/sub\u003e, the RR, the pulse rate (PR), PetCO\u003csub\u003e2\u003c/sub\u003e, BP, and subjective sensation scores for dyspnoea, palpitation and headache. Venous blood (1 ml) was collected from the participants, and baseline values for the no-mask condition were measured using a blood gas analyser (Cobas b 123, Roche Diagnostics). The pH, PvO\u003csub\u003e2\u003c/sub\u003e, venous carbon dioxide partial pressure (PvCO\u003csub\u003e2\u003c/sub\u003e), and bicarbonate (HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) levels were recorded. To reduce harm to the subjects, baseline venous blood gas analysis was performed only once. Subsequently, the abovementioned data were collected using the same method immediately after mask wearing (T1) (after three regular breaths) and after continuous mask wearing for 1 hour (T2), 2 hours (T3), 3 hours (T4), and 4 hours (T5). To minimize data variability, data were collected twice at each time point, after which the average value was calculated. After continuously wearing an SM or N95 mask for 4 hours, 1 ml of venous blood was extracted for blood gas analysis. All subjective sensations were scored by means of a 10-point visual analogue scale (VAS) from 0 (no discomfort) to 10 (worst discomfort imaginable).\u003c/p\u003e\n\u003ch3\u003eOutcomes\u003c/h3\u003e\n\u003cp\u003eThe primary outcome was the change in PvCO\u003csub\u003e2\u003c/sub\u003e value after continuous SM and N95 mask wearing for 4 hours. The secondary outcomes were PetCO\u003csub\u003e2\u003c/sub\u003e, SpO\u003csub\u003e2\u003c/sub\u003e, the PR, the RR, BP, and the VAS subjective sensation scores at 5 time points (T1, T2, T3, T4 and T5), as well as the pH, PvO\u003csub\u003e2\u003c/sub\u003e, and HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e of venous blood gas after 4 hours of mask wear.\u003c/p\u003e\n\u003ch3\u003eSample size calculation\u003c/h3\u003e\n\u003cp\u003eThe sample size was calculated with Pass 15 (NCSS, LLC, Kaysville, UT, USA). In our preliminary experiment, six obese anaesthesiologists working in the operating room were included; after 4 hours of the intervention, the difference in the PvCO\u003csub\u003e2\u003c/sub\u003e between the SM and N95 mask groups was 1.5 (1.3) mmHg. With a two-sided test, an α of 5%, and a power of 90%, 18 participants were needed. Assuming a 10% dropout rate, we included a total of 20 participants.\u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed using R software (version 4.3.1). Categorical data are represented as numbers or percentages. Continuous data were tested for normality using the Shapiro-Wilk test and are expressed as the mean (standard deviation) or median (interquartile range [IQR]). A linear mixed model (eSupplementary 1) was established the differences in physiological changes caused by N95 masks and SMs, as well as the differences in physiological changes caused by different intervention measures within subjects over time, while considering the internal correlations among subjects caused by cross design and repeated measurements. We modeled the cyclical and carryover effects, and used the FDR method for correction after multiple comparisons. A \u003cem\u003eP\u003c/em\u003e value of \u0026lt;\u0026thinsp;0.05 was considered to indicate statistical significance.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eBetween July 2023 and October 2023, among 199 operating room medical staff, 33 obese medical staff were assessed for eligibility. As described in the flowchart (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), 13 participants were excluded, and ultimately 20 obese participants were randomized.\u003c/p\u003e\n\u003ch3\u003eBasic characteristics\u003c/h3\u003e\n\u003cp\u003eTwenty obese participants in the operating room (mean [SD] age, 32.2 [6.0] years; 9 women [45%]) completed this study, with an average BMI of 32.8 (SD, 2.1) kg/m\u003csup\u003e2\u003c/sup\u003e. There were no significant differences in baseline values for age, height, weight, BMI, venous blood gas or physiological indicators between the SM-first group and the N95 mask-first group (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\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\u003eBaseline characteristics of the participants.\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=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCharacteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal participants\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSM-first group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN95 mask-first group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo. (%) of participants (n\u0026thinsp;=\u0026thinsp;20)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20 (100)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10 (50)\u003c/p\u003e \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\u003eSex\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\u003eFemale (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9 (45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 (40)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5 (50)\u003c/p\u003e \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\u003eMale (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (55)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 (60)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5 (50)\u003c/p\u003e \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\u003eAge, years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.2 (6.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.2 (4.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e33.2 (7.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.467\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeight, cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e168.6 (6.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e169.9 (7.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e167.4 (5.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.377\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeight, kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e93.8 (11.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e95.9 (13.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e91.6 (9.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.425\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI, kg/m\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.8 (2.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.0 (2.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32.6 (1.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.701\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePvCO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e47.1 (4.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e46.9 (5.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e47.3 (2.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.811\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.353 (0.037)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.356 (0.046)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.350 (0.026)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.752\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePvO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e39.0 (3.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.8 (4.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e39.1 (3.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.863\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (mmol/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.2 (1.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25.2 (1.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e25.2 (0.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.928\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePetCO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37.4 (2.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e37.4 (3.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37.5 (2.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.904\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpO\u003csub\u003e2\u003c/sub\u003e (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e97.1 (1.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e97.0 (0.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e97.2 (1.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.575\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRR (breaths/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17.1 (2.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16.4 (2.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17.9 (2.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.220\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePR (beats/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e83.4 (12.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e81.8 (9.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e85. 0 (15.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.582\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSBP (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e119.3 (10.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e121.8 (10.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e116. 8 (9.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.283\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDBP (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e76.7 (7.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e77.9 (8.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e75.5 (6.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.483\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eValues are presented as the mean (SD) and number of patients (%).\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eAbbreviations: BMI, body mass index; SM, surgical mask; PvCO\u003csub\u003e2\u003c/sub\u003e, venous carbon dioxide partial pressure (PvCO\u003csub\u003e2\u003c/sub\u003e); HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, bicarbonate; PvO\u003csub\u003e2\u003c/sub\u003e, venous oxygen pressure; PetCO\u003csub\u003e2\u003c/sub\u003e, partial pressure of end-tidal carbon dioxide; SpO\u003csub\u003e2\u003c/sub\u003e, peripheral blood oxygen saturation; RR, respiratory rate; PR, pulse rate; SBP, systolic blood pressure; DBP, diastolic blood pressure.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eDifferences between the SM-first group and the N95 mask-first group were tested by independent-sample t test.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003ePrimary Outcome Measure\u003c/h3\u003e\n\u003cp\u003eEstimates of mean changes between baseline and 4 hours of mask intervention obtained from the repeated measures analysis are reported in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. There was a significant difference in the primary outcome measure (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), changes in average PvCO\u003csub\u003e2\u003c/sub\u003e, between N95 masks (3.3 [2.2, 4.4]) and SM (1.9 ([0.9, 3.00]). Compared to continuously wearing SMs 4 hours, N95 mask wear for 4 hours significantly increased PvCO\u003csub\u003e2\u003c/sub\u003e [49.0 (3.8) vs. 50.4 (4.0), \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001] (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Baseline venous blood gas was only collected once in both groups. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the PvCO\u003csub\u003e2\u003c/sub\u003e values of the N95 mask group were significantly higher in both stage 1(Mean [95% CI], 1.6 [0.9, 2.3], \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and stage 2 (Mean [95% CI], 1.1 [0.0, 2.2], \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.044 ), indicating that the N95 mask had a more significant treatment effect (eTable 2).\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\u003eEstimated mean changes of all outcome measures between baseline and 4 hours.\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eOutcome\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003eEstimated change between baseline and 4 h, mean (95% CI)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSM group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN95 mask group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSM vs N95 group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePvCO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.9 (0.9, 3.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.3 (2.2, 4.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.4 (0.8, 1.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.008 (-0.023, 0.008)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-0.016 (-0.031, 0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.008 (-0.016, 0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.078\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePvO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-1.3 (-2.3, -0.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-1.3 (-2.4, -0.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.1 (-0.5, 0.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.822\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (mmol/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.6 (0, 1.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.8 (0.3, 1.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.2 (-0.1, 0.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.229\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePetCO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.2 (2.3, 4.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.3 (2.4, 4.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0 (-0.3, 0.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.886\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpO\u003csub\u003e2\u003c/sub\u003e (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.3 (-0.7, 0.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0 (-0.4, 0.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.3 (-0.1, 0.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.180\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRR (breaths/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.2 (0.6, 1.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.8 (1.2, 2.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.6 (0.1, 1.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.023\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePR (beats/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-1.9 (-4.8, 1.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-1.6 (-4.6, 1.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.3 (-2.2, 2.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.840\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSBP (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-1.1 (-4.4, 2.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-0.2 (-3.5, 3.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9 (-3.1, 4.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.676\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDBP (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-1.3 (-5.2, 2.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.7 (-3.2, 4.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2 (-2.6, 6.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.400\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVAS of Dyspnea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.8 (1.4, 2.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.9 (2.5, 3.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.1 (0.8, 1.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVAS of Headache\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.9 (1.6, 2.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.9 (2.6, 3.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.0 (0.7, 1.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVAS of Palpitation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.4 (1.1, 1.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.4 (2.1, 2.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.0 (0.7, 1.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eThe primary outcome was PvCO\u003csub\u003e2\u003c/sub\u003e. All other variables were secondary outcomes.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eEstimates were obtained using a repeated-measures modeling framework.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eAbbreviations: SM, surgical mask; CI, confidence interval; PvCO\u003csub\u003e2\u003c/sub\u003e, venous carbon dioxide partial pressure; HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, bicarbonate; PvO\u003csub\u003e2\u003c/sub\u003e, venous oxygen pressure; PetCO\u003csub\u003e2\u003c/sub\u003e, partial pressure of end-tidal carbon dioxide; SpO\u003csub\u003e2\u003c/sub\u003e, peripheral blood oxygen saturation; RR, respiratory rate; PR, pulse rate; SBP, systolic blood pressure; DBP, diastolic blood pressure; VAS, visual analogue scale.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eSecondary Outcome Measures\u003c/h3\u003e\n\u003cp\u003eThe treatment effect, period effect, and carryover effect of secondary outcome measures in crossover study were validated (eTable 2). Estimates of mean changes between baseline and 4 hours for secondary outcome measures are presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. After continuous masks wearing for 4 hours, there was no significant difference in the changes in venous blood gas pH, PvO\u003csub\u003e2\u003c/sub\u003e, HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, and physiological indices such as PetCO\u003csub\u003e2\u003c/sub\u003e, RR, PR, SpO\u003csub\u003e2\u003c/sub\u003e, and BP between the two groups. The pH, PvO\u003csub\u003e2\u003c/sub\u003e, HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e changes between the two groups in stage 1 and stage 2 were also not significant (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and eTable 3, at each time point, intergroup comparisons were made between SM and N95 mask interventions, and the results showed that there were no significant differences in PetCO\u003csub\u003e2\u003c/sub\u003e, RR, SpO\u003csub\u003e2\u003c/sub\u003e, SBP, and DBP. Both groups showed a significant increase in PetCO\u003csub\u003e2\u003c/sub\u003e (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) immediately after donning an SM or N95 mask (T1). After continuous wearing of masks for 4 hours (T5), the estimated mean change in PR between baseline and N95 mask group was significantly increased than that of the SM group (Mean [95% CI], 0.6 [0.1, 1.1], \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.023).\u003c/p\u003e\u003cp\u003eAt each time point, the mean estimated changes in VAS scores for dyspnoea, headache and palpitations were compared between the N95 mask and SM groups at baseline and that time point (Fig.\u0026nbsp;4). With prolonged SM and N95 mask wear, the VAS scores of the obese operating room staff for dyspnoea, palpitations and headache gradually increased. Intergroup comparisons revealed significant differences (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) in the VAS scores for the three subjective sensations between the two mask interventions at 2, 3, and 4 hours (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;4). With increasing mask use duration, the subjective VAS scores of participants in the N95 mask group increased more significantly than did those of participants in the SM group, but the scores remained tolerable (mean VAS score, \u0026lt; 3).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eObesity and mask use may both increase the cardiopulmonary burden [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. This study investigated the physiological effects of SM and N95 mask wearing on obese operating room staff through self-comparison.\u003c/p\u003e \u003cp\u003eThis crossover trial showed that continuous SM or N95 masks wearing for 4 hours significantly increased PvCO2, PetCO\u003csub\u003e2\u003c/sub\u003e, and RR in obese operating room staff. Compared with SM, N95 masks wearing had a more significant effect on PvCO\u003csub\u003e2\u003c/sub\u003e, but there was no significant difference in other venous blood gas and physiological indices between the two types of masks. Combined with the venous blood indices, these changes are unlikely to have clinical significance. We also observed a significant increase in the PetCO\u003csub\u003e2\u003c/sub\u003e immediately after SM and N95 mask wearing compared to no mask wearing. This change may be related to psychological factors, and the increase in the RR may be a compensatory mechanism for the increase in PetCO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAfter continuous mask wearing for 2 hour, the subjective VAS scores of obese participants in the N95 mask group were significantly greater than those in the SM group; however, all of these scores were within a tolerable range. Indicating that the subjective discomfort of the two types of masks will not seriously affect obese medical staff in the operating room.\u003c/p\u003e \u003cp\u003eThe impact of SMs or N95 masks on healthy nonobese healthcare workers has been extensively confirmed [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. A study of ICU medical staff confirmed that wearing N95 masks for prolonged work did not result in a significant decrease in SpO\u003csub\u003e2\u003c/sub\u003e or a significant increase in heart rate [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. These research results are basically consistent with our research data, indicating that it is safe for obese health care workers without a history of cardiopulmonary disease to use masks for extended periods during daily medical activities.\u003c/p\u003e \u003cp\u003eHowever, studies on the impact of masks on obese people are rare. A study showed that obese children were more likely to experience respiratory distress while wearing masks. After walking tests, overweight or obese children showed a significant increase in PetCO\u003csub\u003e2\u003c/sub\u003e and in the PR and RR, but no significant changes in SpO\u003csub\u003e2\u003c/sub\u003e were observed [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Consistent with our research findings, they also observed a significant increase in PetCO\u003csub\u003e2\u003c/sub\u003e when obese children used masks immediately.\u003c/p\u003e \u003cp\u003eIn healthy individuals, N95 masks cause minimal changes in blood gas and other physiological parameters during physical activity, even during very intense exercise[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. A recent study of healthy volunteers suggested that even with mild exercise, prolonged wear of N95 masks can increase respiratory resistance, leading to a decrease in RR and SpO\u003csub\u003e2\u003c/sub\u003e within 1 hour and an increase in heart rate after 2 hours until the mask is removed [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Consistent with our research findings, this study also did not find any changes in BP, as healthy individuals can compensate for this cardiovascular overload.\u003c/p\u003e \u003cp\u003eAlthough our data support that SMs and N95 masks have a smaller impact on physiological indices, N95 masks have higher subjective sensation scores, which are related to tighter facial seals. After wearing N95 masks for 4 hours, the inhalation and exhalation resistance increased by 0.43 and 0.23 mmH\u003csub\u003e2\u003c/sub\u003eO, respectively. The average moisture retention in the mask is 0.26 ml [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Compared to no mask, N95 masks increase the temperature of inhaled air by 1.13 times during eight breaths and increase the CO\u003csub\u003e2\u003c/sub\u003e concentration by 7.3 times [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. An increase in heat and humidity inside N95 masks directly leads to an increase in respiratory resistance, repeated CO\u003csub\u003e2\u003c/sub\u003e breathing, and an increase in subjective sensations such as dyspnoea.\u003c/p\u003e \u003cp\u003eBased on the findings of our study, we believe that headaches are unlikely to be caused by physiological changes in the balance of O\u003csub\u003e2\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e and may be due to facial pain behind the ears or other contact points caused by mask straps.[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] Indirect factors, such as insufficient hydration and an irregular diet, may also lead to headaches when individuals wear masks for a long time [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Recent research data suggest that prolonged use of masks in medical environments has limited effects on the PR and HR of healthcare workers. Although the subjective perception score for palpitations significantly increases, more consideration should be given to psychological factors [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMasks are usually used to prevent respiratory virus infections, but their effectiveness may vary depending on the type of mask used. There is currently insufficient evidence supporting the use of medical masks or SMs to combat influenza or coronavirus infections, with N95 masks being the most effective [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Our research suggested that there was almost no difference in the impact of SMs or N95 masks on the physiological indicators of obese healthcare workers. These findings may help to persuade obese healthcare workers to wear N95 masks for better protection.\u003c/p\u003e \u003cp\u003eOur research advantage lies in the monitoring of obese medical staff during daily medical work in the operating room rather than during intense exercise or running, which has more practical significance for clinical guidance. This study has several limitations. First, venous blood was used for blood gas analysis to increase the comfort of the study participants. We were only observing the differences in several blood gas indicators in the mask group, not for therapeutic purposes. Second, due to the small sample size, sex and age subgroup analysis was not conducted. Third, we only observed participants for 4 hours and did not collect data on the safety of using masks for longer periods, as masks are disposable, and their protective effects weaken over time; it is generally recommended that masks be replaced every 4 hours [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Finally, to minimize interference with surgery, obese surgeons were not included in this study, which affected the generalizability of the results.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eObese operating room staff who participate in routine medical work can wear SMs or N95 masks for 4 hours without significantly increasing the risk of physiological burden. It is recommended that N95 masks be worn under high-risk conditions for better protection and replaced every 4 hours according to established guidelines. Future research should focus on the effects of masks on sex and age differences.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe protocol was approved by the Qilu Hospital of Shandong University Medical Ethics Committee (No. KYLL-202306-032), and each participant provided written informed consent. All studies were carried out in accordance with the Declaration of Helsinki (2013 Edition).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used in the present study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclarations of interest\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003cp\u003e\u0026nbsp;This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003cp\u003e\u0026nbsp;Data collection: CYF and YL\u003c/p\u003e\n\u003cp\u003eStatistical analysis: YLG and YZB\u003c/p\u003e\n\u003cp\u003eWriting of the manuscript: SZY and YL\u003c/p\u003e\n\u003cp\u003eInception of the study idea: SZY and CYF\u003c/p\u003e\n\u003cp\u003eStudy design: SZY and CYF\u003c/p\u003e\n\u003cp\u003eRevision of the manuscript: SZY and YL\u003c/p\u003e\n\u003cp\u003eAll the authors approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003eThe authors thank all the involved obese operating room staff for their contributions to this trial.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePan X-F, Wang L, Pan A. Epidemiology and determinants of obesity in China. Lancet Diabetes Endocrinol. 2021;9(6):373\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJaacks LM, Vandevijvere S, Pan A, McGowan CJ, Wallace C, Imamura F, Mozaffarian D, Swinburn B, Ezzati M. The obesity transition: stages of the global epidemic. Lancet Diabetes Endocrinol. 2019;7(3):231\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnderson MR, Shashaty MGS. Impact of Obesity in Critical Illness. Chest. 2021;160(6):2135\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKunyahamu MS, Daud A, Jusoh N. Obesity among Health-Care Workers: Which Occupations Are at Higher Risk of Being Obese? Int J Environ Res Public Health 2021, 18(8).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSharma SV, Upadhyaya M, Karhade M, Baun WB, Perkison WB, Pompeii LA, Brown HS, Hoelscher DM. Are Hospital Workers Healthy? A Study of Cardiometabolic, Behavioral, and Psychosocial Factors Associated With Obesity Among Hospital Workers. J Occup Environ Med. 2016;58(12):1231\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSteege AL, Boiano JM, Sweeney MH. Secondhand smoke in the operating room? Precautionary practices lacking for surgical smoke. Am J Ind Med. 2016;59(11):1020\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLeung NHL, Chu DKW, Shiu EYC, Chan KH, McDevitt JJ, Hau BJP, Yen HL, Li Y, Ip DKM, Peiris JSM, et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med. 2020;26(5):676\u0026ndash;80.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoszkowicz D, Hobeika C, Collard M, Bruzzi M, Beghdadi N, Catry J, Duchalais E, Manceau G, Voron T, Lakkis Z, et al. Operating room hygiene: Clinical practice recommendations. J Visc Surg. 2019;156(5):413\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eScheid JL, Lupien SP, Ford GS, West SL. Commentary: Physiological and Psychological Impact of Face Mask Usage during the COVID-19 Pandemic. Int J Environ Res Public Health 2020, 17(18).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKisielinski K, Giboni P, Prescher A, Klosterhalfen B, Graessel D, Funken S, Kempski O, Hirsch O. Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards? Int J Environ Res Public Health 2021, 18(8).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBeder A, B\u0026uuml;y\u0026uuml;kko\u0026ccedil;ak U, Sabuncuoğlu H, Keskil ZA, Keskil S. Preliminary report on surgical mask induced deoxygenation during major surgery. Neurocirugia (Astur). 2008;19(2):121\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang S, Fang C, Liu X, Liu Y, Huang S, Wang R, Qi F. Surgical Masks Affect the Peripheral Oxygen Saturation and Respiratory Rate of Anesthesiologists. Front Med (Lausanne). 2022;9:844710.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlkhalaf A, Aljaroudi E, Al-Hulami M, Gaffar B, Almas K. Efficacy of Surgical Masks Versus N95 Respirators for the Prevention of COVID-19 in Dental Settings: A Systematic Review. Cureus. 2023;15(4):e37631.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGriswold DP, Gempeler A, Kolias A, Hutchinson PJ, Rubiano AM. Personal protective equipment for reducing the risk of COVID-19 infection among health care workers involved in emergency trauma surgery during the pandemic: An umbrella review. J Trauma Acute Care Surg. 2021;90(4):e72\u0026ndash;e80.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRebmann T, Carrico R, Wang J. Physiologic and other effects and compliance with long-term respirator use among medical intensive care unit nurses. Am J Infect Control. 2013;41(12):1218\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShechtman L, Ben-Haim G, Ben-Zvi I, Steel L, Ironi A, Huszti E, Chatterji S, Levy L. Physiological Effects of Wearing N95 Respirator on Medical Staff During Prolong Work Hours in Covid-19 Departments. J Occup Environ Med. 2022;64(6):e378\u0026ndash;80.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSu CY, Peng CY, Liu HL, Yeh IJ, Lee CW. Comparison of Effects of N95 Respirators and Surgical Masks to Physiological and Psychological Health among Healthcare Workers: A Randomized Controlled Trial. \u003cem\u003eInt J Environ Res Public Health\u003c/em\u003e 2021, 18(24).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSingla M, Soni RK, Chhina RS, Chhabra ST, Wander GS. Impact of long duration wearing of N95 masks on cardiorespiratory system and subjective sensations of health-care workers during COVID-19 era. J Anaesthesiol Clin Pharmacol. 2022;38(4):599\u0026ndash;604.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLubrano R, Bloise S, Marcellino A, Ciolli CP, Testa A, De Luca E, Dilillo A, Mallardo S, Isoldi S, Martucci V, et al. Effects of N95 Mask Use on Pulmonary Function in Children. J Pediatr. 2021;237:143\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHopkins SR, Dominelli PB, Davis CK, Guenette JA, Luks AM, Molgat-Seon Y, S\u0026aacute; RC, Sheel AW, Swenson ER, Stickland MK. Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease. Ann Am Thorac Soc. 2021;18(3):399\u0026ndash;407.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBao R, Ning G, Sun Y, Pan S, Wang W. Evaluation of Mask-Induced Cardiopulmonary Stress: A Randomized Crossover Trial. JAMA Netw Open. 2023;6(6):e2317023.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRoberge RJ, Bayer E, Powell JB, Coca A, Roberge MR, Benson SM. Effect of exhaled moisture on breathing resistance of N95 filtering facepiece respirators. Ann Occup Hyg. 2010;54(6):671\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSalati H, Khamooshi M, Vahaji S, Christo FC, Fletcher DF, Inthavong K. N95 respirator mask breathing leads to excessive carbon dioxide inhalation and reduced heat transfer in a human nasal cavity. Phys Fluids (1994). 2021;33(8):081913.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOng JJY, Bharatendu C, Goh Y, Tang JZY, Sooi KWX, Tan YL, Tan BYQ, Teoh HL, Ong ST, Allen DM, et al. Headaches Associated With Personal Protective Equipment - A Cross-Sectional Study Among Frontline Healthcare Workers During COVID-19. Headache. 2020;60(5):864\u0026ndash;77.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSheng Chew NW, Chiew Wong RC, Djohan AH, Ngiam JN, Chai P, Yeo TC, Tan HC, Sia CH. Association of face mask use with self-reported cardiovascular symptoms during the COVID-19 pandemic. Singap Med J. 2023;64(10):609\u0026ndash;15.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim MS, Seong D, Li H, Chung SK, Park Y, Lee M, Lee SW, Yon DK, Kim JH, Lee KH, et al. Comparative effectiveness of N95, surgical or medical, and non-medical facemasks in protection against respiratory virus infection: A systematic review and network meta-analysis. Rev Med Virol. 2022;32(5):e2336.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLoveday HP, Wilson JA, Pratt RJ, Golsorkhi M, Tingle A, Bak A, Browne J, Prieto J, Wilcox M. Health UKDo: epic3: national evidence-based guidelines for preventing healthcare-associated infections in NHS hospitals in England. J Hosp Infect. 2014;86(Suppl 1):1\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"obesity, surgical mask, N95 mask, venous carbon dioxide partial pressure, end-tidal carbon dioxide partial pressure, physiological impacts","lastPublishedDoi":"10.21203/rs.3.rs-4006747/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4006747/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eObesity and mask both may increase the cardiopulmonary burden on medical staff. The physiological impact of surgical masks (SMs) and N95 masks on obese operating room staff remains uncertain. This study aimed to determine whether wearing N95 masks for 4 hours significantly affected physiological indices in obese medical staff compared to surgical masks (SMs).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this randomized controlled two-phase crossover trial, the physiological impacts of wearing SMs and N95 masks for 4 hours was analysed among 20 obese operating room staff. The primary outcome was the change in venous carbon dioxide partial pressure (PvCO\u003csub\u003e2\u003c/sub\u003e) levels at 4-hour intervention. Secondary outcomes included venous oxygen pressure (PvO\u003csub\u003e2\u003c/sub\u003e), bicarbonate (HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e−\u003c/sup\u003e) and pH levels at 4-hour intervention, end-tidal carbon dioxide partial pressure (PetCO\u003csub\u003e2\u003c/sub\u003e), peripheral oxygen saturation (SpO\u003csub\u003e2\u003c/sub\u003e), respiratory rate (RR), pulse rate (PR) and blood pressure (BP) at immediately, 1 h, 2 h, 3 h, and 4 h after mask wear. Dyspnoea, palpitations, headache were assessed with the visual analogue scale (VAS) score. Linear mixed models were used for comparative analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTwenty participants (age 32.2 [6.0] years; BMI 32.8 [2.1] kg/m\u003csup\u003e2\u003c/sup\u003e; 45% female) completed the study. Compared with the no-mask condition, both SM and N95 masks wearing for 4 hours caused PvCO\u003csub\u003e2\u003c/sub\u003e, HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e−\u003c/sup\u003e, PetCO\u003csub\u003e2\u003c/sub\u003e, and RR levels increased slightly in obese operating room staff. N95 masks had a statistically significant rather than clinically significant impact on PvCO\u003csub\u003e2\u003c/sub\u003e (mean [95% CI], 1.4 [0.8, 1.9], \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.001) and RR (0.6 [0.1, 1.1)], \u003cem\u003eP\u003c/em\u003e = 0.023) compared with SM. There was no significant difference between the two types of masks in terms of PvO\u003csub\u003e2\u003c/sub\u003e, pH, SpO\u003csub\u003e2\u003c/sub\u003e, PR, and BP. The three subjective VAS scores gradually increased over wear time. After more than 2 hours, the N95 group showed significantly increased than SM group.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eObese operating room staff continuously wearing SM or N95 masks 4 hours showed almost no difference in physiological impacts. It is recommended to wear N95 masks under high-risk conditions for better protection.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial registration\u003c/strong\u003e: NCT05950256.\u003c/p\u003e","manuscriptTitle":"Physiological Impact of N95 Masks on Obese Operating Room Staff: A Randomized Crossover Trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-06 19:25:00","doi":"10.21203/rs.3.rs-4006747/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a66bbea5-15c6-4872-a4d3-3a10070938f3","owner":[],"postedDate":"March 6th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-03-07T16:34:16+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-06 19:25:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4006747","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4006747","identity":"rs-4006747","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}