The Impact of Semi-upright Position on Severity of Sleep Disordered Breathing in Patients with Obstructive Sleep Apnea: A two-arm, prospective, randomized controlled trial

The Impact of Semi-upright Position on Severity of Sleep Disordered Breathing in Patients with Obstructive Sleep Apnea: A two-arm, prospective, randomized controlled 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 The Impact of Semi-upright Position on Severity of Sleep Disordered Breathing in Patients with Obstructive Sleep Apnea: A two-arm, prospective, randomized controlled trial Gincy Ann Lukachan, Azadeh Yadollahi, Dennis Auckley, Bojan Gavrilovic, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2278755/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Jul, 2023 Read the published version in BMC Anesthesiology → Version 1 posted 10 You are reading this latest preprint version Abstract Background The severity of sleep-disordered breathing is known to worsen postoperatively and is associated with increased cardio-pulmonary complications and increased resource implications. In the general population, the semi-upright position has been used in the management of OSA. We hypothesized that the use of a semi-upright position versus a non-elevated position will reduce postoperative worsening of OSA in patients undergoing non-cardiac surgeries Methods This study was conducted as a prospective randomized controlled trial of perioperative patients, undergoing elective non-cardiac inpatient surgeries. Patients underwent a preoperative sleep study using a portable polysomnography device. Patients with OSA (apnea hypopnea index (AHI) >5 events/hr), underwent a sleep study on postoperative night 2 (N2) after being randomized into an intervention group (Group I): semi-upright position (30 to 45 degrees incline), or a control group (Group C) (zero degrees from horizontal). The primary outcome was postoperative AHI on N2. The secondary outcomes were obstructive apnea index (OAI), central apnea index (CAI), hypopnea index (HI), obstructive apnea hypopnea index (OAHI) and oxygenation parameters. Results: Thirty-five patients were included. Twenty - one patients were assigned to the Group 1 (females-14 (67%); mean age 65±12) while there were fourteen patients in the Group C (females-5 (36%); mean age 63±10). The semi-upright position resulted in a significant reduction in OAI in the intervention arm (Group C vs Group I postop AHI: 16.6 ± 19.0 vs 8.6 ± 11.2 events/hr; overall p = 0.01), but there were no significant differences in the overall AHI or other parameters between the two groups. Subgroup analysis of patients with “supine related OSA” revealed a decreasing trend in postoperative AHI with semi-upright position, but the sample size was too small to evaluate statistical significance. Conclusion: In patients with newly diagnosed OSA, the semi-upright position resulted in improvement in obstructive apneas, but not the overall AHI. Study registration This trial was retrospectively registered in clinicaltrials.gov NCT02152202 on 02/06/2014. Obstructive sleep apnea supine-related OSA surgery elevated position positional therapy Figures Figure 1 Figure 2 Figure 3 Introduction Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder, associated with increased morbidity and mortality in the general and surgical population(1,2) in the perioperative period.(3) It is an independent risk-factor for post-operative cardiac and respiratory complications(4–7) resulting in increased utilization of health care resources.(8) The screening and treatment of OSA is found to be cost effective on the lifetime horizon.(9) According to the current guidelines adult patients at risk of OSA should be screened preoperatively using validated tools such as STOP-Bang, P-SAP, Berlin, and ASA Check List.(10) The American Society of Anesthesiology (ASA) practice guidelines on the perioperative management of OSA advice to consider the initiation of continuous positive airway pressure (CPAP) therapy preoperatively in patients with newly detected severe OSA.(11) , Despite improvement in OSA severity and oxygenation with CPAP, poor patient compliance has been a hurdle to their use in the perioperative period.(12,13) Other alternatives to OSA treatment, such as weight reduction,(14) custom-made orthodontic appliances(15), and surgery (orthodontic surgery,(16) uvulopalatopharyngeoplasty,(17) tonsillectomy,(18) or bariatric surgery(19)) are not feasible in the preoperative period. There is a need for alternative approaches for the management of OSA in surgical patients. Positional therapy could be a useful intervention in surgical patients with OSA in the perioperative period.(20) This option may be more feasible in the postoperative setting as it is cost-effective, easy to administer, and can be adjusted to allow patient comfort. In the general population, sleeping in the non-supine and elevated posture was found to be effective in reducing OSA severity.(21–23) The utility of positional therapy may be greater in patients with supine-related OSA. Supine-related OSA is defined as Apnea-hypopnea index (AHI) > 5 events/hr, and where the supine AHI was more than twice the AHI of the non-supine AHI, and the non-supine AHI was less than 5 events/hr.(24,25) The American Society of Anesthesiology practice guidelines on the perioperative management of OSA recognized that positional therapy may improve the AHI in patients with OSA, but acknowledged that the literature was “insufficient to evaluate the effects of positioning adult OSA patients in the postoperative setting”.(11) We hypothesized that the use of a semi-upright position versus a supine position will prevent postoperative worsening of OSA in patients undergoing non-cardiac surgeries. The objective of the study was to determine whether a semi-upright versus supine position while asleep helps decrease the postoperative worsening of AHI in surgical patients with newly diagnosed OSA. The secondary objective was to study the impact of the semi-upright position in a subgroup of patients with supine-related OSA. Methods Study design This was a two-arm, prospective, randomized controlled, proof of concept trial. The intervention was patient positioning in a semi-upright position (Group I: intervention, head-end elevation 30 to 45 degrees from horizontal), compared to supine position (Group C: control). Study setting This study was conducted at Toronto Western Hospital and Mount Sinai Hospital in Toronto, over a period of seven months. Institutional Review Board approval was obtained from both hospitals prior to start of this study (University Health Network 11-0056AE and Mount Sinai Hospital 11-0021-E). This trial was registered at www.clincialtrials.gov (NCT02152202). The inclusion criteria of patients were adult patients, American Society of Anesthesiologists (ASA) physical status I to IV, undergoing elective inpatient non-cardiac surgery with newly diagnosed OSA. The exclusion criteria were: patients with OSA on treatment (continuous positive airway pressure (CPAP), oral appliance, or previous OSA surgery); known cervical, shoulder, spine abnormalities, and/or chronic pain predisposing to difficulty in maintaining a sitting position and specific types of surgery, such as hip or spine, where a sitting position would be contraindicated postoperatively. Patients were screened by using the STOP-Bang questionnaire.(26) Patients identified as high risk of OSA (STOP-Bang score of three or greater) were consented to undergo a home portable polysomnography (PSG) and OSA status was confirmed by an AHI over 5 events per hour. Patient Recruitment, Intervention and Follow-up Portable PSG was performed using a 10-channel portable PSG device (Embletta X100; Embla, Broomfield, CO). The PSG was obtained preoperatively (preop) at home and on postoperatively (postop) on N 2. (27) The Embletta X100 is a level 2 diagnostic tool for OSA and has been validated against laboratory PSG.(28) The PSG recording montage comprised two electroencephalographic channels (C3 and C4), left or right electro-oculogram, chin muscle electromyogram, nasal cannula (pressure), thoracic and abdominal respiratory effort bands, body-position sensor, and pulse oximetry. At bedtime, the portable PSG device was connected to the patient by a PSG technician at their home. Patients were taught how to disconnect the device, which was picked up by the same sleep technician the following morning. The portable PSG recording was scored by a certified PSG technologist who was supervised by a sleep physician. Apneas were defined as a reduction in airflow from intranasal pressure of at least 90% for 10 seconds or longer, and hypopneas as reduction in flow of at least 30% for 10 seconds or longer, associated with ≥ 4% oxygen desaturation.(29) Apneas and hypopneas were classified as either obstructive (presence of breathing effort) or central (absence of breathing effort) events. Mixed apneas were classified for events that began as central for at least 10 seconds and ended as obstructive, with a minimum of three obstructive efforts. AHI was the average number of apnea and hypopnea episodes per hour of recording. Apnea index was calculated as the average number of apnea episodes per hour. Hypopnea index was the average number of hypopnea episodes per hour. The secondary outcomes were obstructive apnea index (OAI), calculated as the total number of obstructive apneas divided total sleep time (TST); central apnea index (CAI) calculated as the total number of central apneas per hour; obstructive apnea hypopnea index (OAHI), calculated as the total number of obstructive apneas and hypopneas per hour; oxygen desaturation index (ODI), number of events with oxygen desaturation below 4% threshold per hour, and CT90, cumulative percentage of sleep duration with oxygen desaturation less than 90%. Randomization and allocation concealment Patients with OSA (defined as AHI > 5 events/hr), were randomized into two groups: Control or Intervention groups (computer generated blocks of 8) by the research analyst, who was not involved in group allocation or data collection during the study. Group allocation was concealed using sealed, opaque envelops, and patients were assigned to their group following surgery. In the Control group (Group C), there was no bed elevation, and patients were positioned at bedtime with no head elevation or bed angle to zero degrees from the horizontal. In the Intervention group (Group I), patients were positioned at bedtime in a semi-upright position with bed elevated to 30 to 45 degrees from horizontal. The bed angle was measured by a research assistant using an in-built bed angle monitor, or a goniometer, wherever applicable. The bed angle measurements were performed at night and in the morning to monitor compliance with the allocated bed position. Patients had the option to request changing the bed angle to facilitate recovery from surgery in view of pain and discomfort. Perioperative anesthetic care and postoperative pain management A standardized balanced anesthetic technique was used in all patients per routine care. In general anesthesia (GA), patients received an induction dose of propofol, opioid (fentanyl and/or hydromorphone), an inhalational agent (sevoflurane or desflurane), and a muscle relaxant (rocuronium). The muscle relaxant was reversed with neostigmine and atropine. In regional anesthesia (RA), patients received spinal anesthetic and sedation using midazolam, fentanyl and a propofol infusion (20-150 mcg/kg/min). Use of intrathecal opioid (100 mcg preservative free morphine) was at the discretion of the anesthesiologist. Both groups received intravenous or oral narcotics in the postoperative period guided by the Acute Pain Service team, as per our institutional standard of care. Pain was evaluated on a score of 0–10, with 0 as no pain and 10 as the most excruciating pain. Intravenous morphine by patient-controlled analgesia was initiated when the verbal pain score was 4 or higher. The research assistant visited patients daily to assist them with application and removal of the portable PSG, collect data, and document adverse events during the hospital stay. Target sample size The primary outcome of our study was AHI on postop N2. There was no previous research from the perioperative setting evaluating the impact of body positioning. Previous studies in the general population found that the mean change in AHI between the upright position (6 ± 12 events/hr), and no head elevation (29 ± 6 events/hr), respectively.(23,30) The original sample size calculated in the protocol was 28 in each arm calculated after taking a minimal clinically significant difference (MCSD) of an effect size (change in AHI) of at least 10 events per hour from baseline, a power of 0.9 and a standard deviation of 10, after adjusting for an estimated drop-out, and loss of follow up to a total of 20%. However, the study was terminated early due to concerns with funding, and a final sample size of 32 patients was obtained, which had sufficient power of 0.8, with type 1 error of 0.05. It was decided to proceed with analysis of the data by the senior authors. Statistical analysis Analyses were performed using the SAS 9.2 statistical software for Windows (SAS Institute, Cary, NC) or R (version 3.1.1)(31). The analysis was blinded to allocation until the completion of data accrual period. Because of patient preference and deviation from assignment of intervention, a per-protocol analysis was performed for this study, where patients were analyzed based on the bed angle monitor reading noted in the morning following their PSG to show no deviation from protocol. An intention-to-treat analysis was performed as sensitivity analysis, meaning that all participants were analyzed in the group to which they were randomized. Baseline demographic variables are summarized for the entire study population and by treatment group using standard bivariate methods, as implemented in R package tableone(32). For each variable we include a standardized mean difference, along with a p-value against the null hypothesis of equality between groups. Continuous variables were compared using two-tailed, paired t-tests for variables with normally distributed data and Wilcoxon signed rank test for variables with non-normally distributed data. Pre-defined linear regression was performed for the primary and secondary outcomes, with preop AHI and supine-related OSA as covariates. Supine-related OSA was defined as AHI > 5 events/hr, and where the supine AHI was more than twice the AHI of the non-supine AHI, and the non-supine AHI was less than 5 events/hr. (24) A two-sided p value < 0.05 was considered significant and controlled for repeated observations, wherever applicable. Results Study population Patient recruitment and flow is summarized in Figure 1, based on the CONSORT recommendations. A total of 635 patients were screened preoperatively, with 164 patients giving consent, of which 135 patients completed home PSG study. Eighty-three patients with OSA (AHI > 5 events/hr) were randomized, Group C: 41 and Group I: 42. During the study, six patients in Group C requested to change position to semi-upright position and were allocated to Group I. Complete postoperative N2 PSG data were obtained from 15 and 24 patients for Group C and I, respectively. This was partly because of patient refusal to undergo the PSG postoperatively while recovering from surgery, primarily due to postoperative pain and discomfort. Four patients were excluded as they required oxygen supplementation. Per protocol analysis was done for 14 patients in Group C and 21 patients in Group I. The baseline characteristics for PP and ITT analysis are presented in Table 1, and supplementary table 1, respectively. While randomization led to a more balanced distribution of baseline demographic variables, deviation of protocol resulted in disturbances for the PP analysis where control group had higher neck circumference and lower OAI and CT 90 values (SMD>0.8). The preop PSG (Table 1) data showed no difference in AHI, OAHI, HI between Group C and Group I. The baseline OAI was significantly higher (11.7 ± 9.2 vs. 6.0 ± 3.6 events per hour; p=0.01) while CAI was significantly lower (0.7 ± 1.4 vs 3.7 ± 9.5; p=0.04) in Group I than Group C. The CT90 was significantly higher (3.8 (0.4 - 6.1) % vs. 0.7 (0.1 - 1.2) %; p=0.04) and the lowest SaO 2 was significantly lower (79.1 ± 6.1% vs 83.2 ± 5.0 %; p= 0.04) in Group I vs Group C. Primary outcome. Comparing postop N2 vs preop baseline, the AHI increased in Group C while it decreased in Group I (Table 2). The differences were not significant within the groups or between groups. (Group C: postop AHI vs preop AHI: 28.4 ± 28.1 vs 18.1 ± 13.3 events/hr, p=0.33; Group I: postop AHI vs preop AHI: 20.8 ± 23.8 vs 21.4 ± 13.1; p=0.36); overall p = 0.15. (Fig. 2A) Comparing postop N2 vs preop parameters, the changes in OAI within the two groups were not significant but there was an overall significant change between the two groups (Group C vs Group I: postop AHI 16.6 ± 19.0 vs 8.6 ± 11.2 events/hr); (overall p = 0.01) (Fig. 2B). There were no significant differences in CAI, HI, OAHI within the two groups and between groups (Table 2). Among the oxygenation parameters, CT90 (Supplementary fig. 3) significantly increased postoperatively in both groups (Group C: postop CT90 vs preop : 4.4 ± 4.9% vs 1.3 ± 2.0% , p = 0.003; Group I: postop CT90 vs preop : 15.7 ± 19.8% vs 4.4 ± 4.9% ; p = 0.04), and the average SaO 2 were significantly decreased in the postoperative period for both groups (Group C: postop average SaO 2 vs preop : 90.0 ± 3.6% vs 93.4 ± 1.3% , p=0.01; Group I: postop average SaO 2 vs preop : 90.3 ± 3.8% vs 93.1 ± 2.4% , p=0.002). However, between group comparison did not show a significant difference (Table 2). The other parameters were not significantly different from preop to postop and between the two groups (Table 2). Subgroup analysis. The impact of body position was examined in patients classified as “supine-related OSA” (n=8; Group C: 5 patients, and Group I: 3 patients). There was greater reduction in mean AHI in Group I (postop AHI vs preop AHI: 6.0 ± 3.0 vs 24.3 ± 13.9 events/hr) than in Group C (Fig. 3), but the sample size was too small to evaluate statistical significance. Discussion This is a novel study in the perioperative setting to evaluate the efficacy of semi-upright position postoperatively for management of newly diagnosed OSA. We found that it is feasible to institute positional therapy in the form of semi-upright position in the postoperative period for OSA patients. The elevated position resulted in a significant reduction in OAI by eight events per hour, but not the AHI, CAI, HI, and OAHI. The lack of positive results in AHI may be due to patients in the intervention group had significantly worse OAI, lower SaO 2, and higher CT 90 preoperatively. Nevertheless, in the surgical patients with supine-related OSA, we were able to demonstrate the effectiveness of semi-upright position as the mean AHI decreased by 18 events per hour. Although positive airway pressure (PAP) is the mainstay of treatment for moderate to severe OSA, perioperative adherence has been poor as studies have demonstrated only 34% CPAP adherence(13) and 45% auto-titrated CPAP adherence(33) in patients with newly diagnosed OSA treated with PAP therapy before surgery. This suggests a need for alternative therapies for these patients. We found that positional therapy is a feasible alternative treatment option for OSA patients in the perioperative setting especially in those with supine related OSA. These findings could be explained by the close association of upper airway collapsibility with body, head, and neck positioning.(24) Previous work has suggested that the semi-upright position significantly enlarges the upper airway dimensions.(34) , (35) The mean upper airway volume was greater with 44° head elevation compared to supine position.(35) Mild elevations of the head of the bed by 7.5° were associated with reductions in the AHI and improvements in oxygen parameters.(36) In a randomized crossover study of 30 postpartum women with OSA in the post-anesthesia care unit, 45° elevation of the upper body caused a significant reduction in AHI compared to non-elevated position.(37) A recently published randomized crossover trial among perioperative patients with moderate to severe OSA, compared high-flow nasal cannula (20 l/min with 40% oxygen concentration) with or without 30-degree head-of-bed elevation.(38) Patients were assessed with modified apnea hypopnea index, based exclusively on the airflow signal without arterial oxygen saturation criteria. High-flow nasal cannula caused significant improvement in OSA independently, with an additive effect when combined with 30-degree head-of-bed elevation (compared to Control flow-based AHI reduced by 10.9 (95% CI, 1 to 21) events · h–1, P = 0.028; and 23 (95% CI, 13 to 32) events · h–1, P < 0.001 respectively). Body position may affect factors such as upper-airway passive collapsibility, airway dilator muscle activity, loop gain, and arousal threshold in patients with OSA.(39) These factors may play a role in how elevating th upper body can reduce OSA severity. In patients with OSA, pharyngeal critical closing pressure is higher in the supine position than lateral position.(40) which may be related to reduction in functional residual capacity.(41) An increase in the diaphragmatic descent during the respiratory cycle leads to an increase in lung volume and thus an increase in longitudinal traction on the upper airway which increase upper airway caliber during sleep and anesthesia.(42–44) In addition, rostral fluid shift may worsen OSA severity and thus consolidate the effects of gravity on the propensity of OSA as demonstrated in healthy men(45) , (46) and non-obese men.(47) A retrospective study on OSA patients with upper airway surgery found that the prevalence of positional OSA increased from 26 to 54% in those with persistent OSA at six months.(48) Among the non-responders to OSA surgery, almost 70% of patients were position dependent on preoperative PSG with no improvement at six months postoperatively.(49) This highlights the need to explore positional therapy, especially in those with positional OSA. In a systematic review of positional therapy for OSA, CPAP was better than positional therapy to lower the AHI, while positional therapy was better than inactive controls to lower the AHI and improved daytime sleepiness.(50) Long term compliance and treatment benefit from positional therapy needs to be determined by longitudinal studies, and compared to other modalities such as CPAP. In the general population, patients with supine-related OSA may be a suitable phenotype to benefit from positional therapy.(24) Good initial control of the OSA severity has been demonstrated but there is a lack of long-term compliance and outcome data.(24) The supine-related OSA phenotype can be easily identified on the preoperative sleep study. Though our data was limited, we found that patients with supine-related OSA benefit from postoperative semi-upright position with a reduction in AHI. Thus, we recommend the incorporation of semi-upright positioning as a practical adjunct to the perioperative management of OSA patients. It would be useful in those at high risk of OSA, newly diagnosed OSA or CPAP nonadherent patients. Further studies on custom-made pillows (to allow for elevated head position, or lateral position), tennis ball t-shirt,(21) or body position alarm devices (51) need to be done. There are several limitations to our study. First, our study had a small sample size with limited numbers in patients with supine-related OSA. Second, there can be variability in how the body position is reported and scored on the PSG. We used an accelerometer attached to the portable PSG which was placed on the patient′s chest. In-built automatic position sensors define body position as a categorical variable rather than a continuous variable, and may not reflect the physiological impact of various body positions on the collapsibility of the upper airway.(24) Third, head and neck position can independently influence the AHI.(52) Recording trunk position does not account for the effect of head and neck on upper-airway collapsibility and the impact on OSA severity.(53,54) However, we were able to show that the elevated position resulted in a significant reduction in OAI by eight events per hour. In those with supine-related OSA, we found a non-significant decrease in the mean AHI by 18 events per hour. Conclusion We found that the semi-upright position compared to supine position reduced postoperative OAI, indicating reduction in upper airway collapsibility and obstructive apneas. There was a decreasing trend in postoperative AHI in patients with supine-related OSA. Further studies on postoperative positional therapy are needed. Declarations Ethics approval and consent to participate Ethics approval for this study was provided by Research Ethics Board at Toronto Western Hospital (Approval no. 14–8710.0) and Mount Sinai Hospital (Approval no. 11-0021-E) on June 23, 2011 and June 22, 2011 respectively. The study was registered in clinicaltrials.gov NCT02152202 on 02/06/2014. The study was also done as per the declaration of Helsinki. The benefits and purposes of the study were explained to the patients, and each participant provided written, informed consent. Confidentiality was maintained at all levels of the study by avoiding identifiers and using codes to identify patients. Participants’ involvement in the study was voluntary. Participants who did not wish to participate in the study or who wished to withdraw at any time were informed that they could do so without restriction. Consent for publication Not applicable. Availability of data and materials All data and materials in this manuscript are available from the corresponding author on reasonable request. Competing interests Frances Chung holds the ResMed Research Chair of Anesthesia, sleep and perioperative medicine, consultant to Takeda Pharma. STOP-Bang questionnaire proprietary to University Health Network. Mandeep Singh (MS) currently holds the Canadian Anesthesiologists’ Society Career Scientist Grant and a Merit award from the Department of Anesthesiology and Pain Medicine, University of Toronto (Toronto, Canada) to support academic time. MS also serves on the Medical Advisory Board of Hypersomnia Foundation (Atlanta, GA) on a voluntary basis. Gincy A Lukachan, Azadeh Yadollahi, Dennis Auckley, Bojan Gavrilovic, John Matelski: No competing interests Funding This study was supported by Departmental funds. Mandeep Singh is supported by a Canadian Anesthesiologists’ Society Career Scientist Award and by the Merit Awards Program from the Department of Anesthesiology and Pain Medicine at the University of Toronto. Frances Chung reports having received research support from the University Health Network Foundation (Toronto, ON, Canada) and the Ontario Ministry of Health and Long-Term Care, royalties from UpToDate Inc., and consultant fees from the Takeda Pharmaceutical Company Limited. She is a developer of the STOP-Bang questionnaire (proprietary to the University Health Network). Authors' contributions FC and MS conceptualized the study, acquired funding, designed the methodology, supervised and oversaw the trial, assisted with writing the original draft, reviewed and edited the final manuscript. GAL, AY, DA and JM assisted with data analysis, drafting and revising the article. BG assisted with data collection, data analysis, drafting and revising the article. The author(s) read and approved the final manuscript. Frances Chung and Mandeep Singh shared senior authorship for this study. Acknowledgements We acknowledge the help of Islam Sazzadual, MSc, Babak Amirshahi, MD, Hoda Fazel MD and Hisham Elsaid MD for conduct of the study. We thank Pu Liao MD for database management, Yuming Sun, MD for scoring polysomnography. We acknowledge the help of Colin Shapiro MD for the supervision of polysomnography scoring. Authors and Affiliations Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto. 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Change in position dependency in non-responders after multilevel surgery for obstructive sleep apnea: Analysis of polysomnographic parameters. European Archives of Oto-Rhino-Laryngology. 2014;271(5):1081–5. Srijithesh PR, Aghoram R, Goel A, Dhanya J. Positional therapy for obstructive sleep apnoea. Cochrane Database of Systematic Reviews. 2014;(2). Levendowski DJ, Seagraves S, Popovic D, Westbrook PR. Assessment of a neck-based treatment and monitoring device for positional obstructive sleep apnea. Journal of Clinical Sleep Medicine. 2014;10(8):863–71. van Kesteren ER, van Maanen JP, Hilgevoord AAJ, Laman DM, de Vries N. Quantitative Effects of Trunk and Head Position on the Apnea Hypopnea Index in Obstructive Sleep Apnea. Sleep. 2011;34(8):1075–81. Isono S, Tanaka A, Tagaito Y, Ishikawa T, Nishino T. Influences of head positions and bite opening on collapsibility of the passive pharynx. Journal of Applied Physiology. 2004 Jul;97(United States PT-Journal Article LG-English):339–46. Walsh J. H., Maddison K. J., Platt P. R., Hillman D. R., Eastwood P. R. Influence of Head Extension, Flexion, and Rotation on Collapsibility of the Passive Upper Airway. Sleep. 2008;31(10):1440–7. Tables Table 1. Patient demographics across the two groups (Per-protocol). Control (n=14) Intervention (n=21) P value Standardized Mean Difference Age (years) 63±10 65±12 0.60 0.188 BMI (kg/m 2 ) 32.8±4 35.2±7 0.26 0.420 Neck Circumference (cm) 43.3±3 41.0±3 0.04 0.752 Gender F/M 5/9 14/7 0.09 0.651 STOP-Bang score 4.5±1 4.5±1 0.95 0.020 Co-morbidity Hypertension 7 12 0.74 0.144 Gastroesophageal reflux 2 7 0.26 0.459 Diabetes Mellitus 1 6 0.20 0.583 Smoker 2 2 1.00 0.147 Asthma 1 3 0.64 0.232 COPD 1 1 1.00 0.101 CAD 3 0 0.06 0.739 Type of surgery 0.65 0.707 Orthopedic 8 12 General 5 6 Gynecology 0 2 Urology 1 0 Type of Anesthesia 1.00 0.048 General 7 10 Spinal 7 11 ASA Status 0.16 0.589 II 8 7 III 5 14 Total amount of opioids (in mg IV morphine equivalents) 1 st 24 h 10.3 [5.3 - 19.8] 11.0 [5. - 20] 0.84 0.080 1 st 48 h 21.4 [13.3 – 44.4] 33.4 [15.0 - 55.0] 0.45 0.186 1 st 72 h 25.8 [14.2 - 60.50] 41.4 [25.0 - 81.5] 0.29 0.259 Preoperative sleep study data between the two groups AHI 18.1 ± 13.3 21.4 ± 13.1 0.48 0.246 OAI 6.1 ± 3.7 11.7 ± 9.2 0.04 0.807 OAHI 14.6 ± 7.2 20.7 ± 12.6 0.11 0.593 CAI 3.7 ± 9.5 0.7 ± 1.4 0.16 0.444 HI 8.6 ± 5.2 9.0 ± 7.3 0.84 0.071 ODI 15.5 [13.5 - 23.7] 17.9 [12.1 - 39.1] 0.57 0.281 CT90 0.7 [0.1 - 1.2] 3.8 [0.4 – 6.1] 0.04 0.804 Average SaO2 93.4 ± 1.27 93.1 ± 2.4 0.71 0.137 Lowest SaO2 83.2 ± 5.0 79.1 ± 6.1 0.04 0.748 Data are expressed as mean (SD) or median (interquartile range IQR) where appropriate. Standardized Mean Difference was calculated using R package tableone BMI - body mass index; COPD – chronic obstructive pulmonary disease; CAD – coronary artery disease; OR – operating room; h: hours. AHI: Apnea-Hypopnea Index; Apnea index: average number of apnea episodes per hour; Arousal \index: number of arousals × 60 / Total sleep time; CAI: Central Apnea Index: total number of central apneas per hour; CT90: cumulative percentage of Total sleep time with oxygen desaturation below 90%; HI: Hypopnea index, average number of hypopnea episodes per hour; OAHI: Obstructive Apnea Hypopnea Index, total number of obstructive apneas and hypopneas per hour; OAI: Obstructive Apnea Index: total number of obstructive apneas divided by Total sleep time; ODI: Oxygen Desaturation Index, number of events with oxygen desaturation below 4% threshold in one hour; REM%: Time spent in rapid eye movement stage of sleep; SaO 2 : saturation of oxygen in hemoglobin Table 2: Postoperative sleep-related outcomes in both groups Control (n = 14) Intervention (n = 21) Between group comparison (ANCOVA) Variable Pre-op Post-op p-value Pre-op Post-op p-value p-value AHI 18.1 ± 13.3 28.4 ± 28.1 0.33 21.4 ± 13.1 20.8 ± 23.8 0.36 0.15 OAI 6.0 ± 3.6 16.6 ± 19.0 0.09 11.7 ± 9.2 8.6 ± 11.2 0.13 0.01* CAI 3.7 ± 9.5 3.6 ± 4.9 0.35 0.7 ± 1.4 1.3 ± 3.5 0.79 0.11 HI 8.6 ± 5.2 8.6 ± 8.4 0.9 9.0 ± 7.3 11.3 ± 11.4 0.34 0.49 OAHI 14.6 ± 7.2 25.2 ± 24.2 0.14 20.7 ± 12.6 19.8 ± 21.5 0.54 0.09 ODI 19.3 ± 12.5 26.2 ± 24.7 0.39 23.1 ± 14.3 26.1 ± 27.1 0.66 0.55 CT90 1.3 ± 2.0 28.1 ± 35.4 0.003* 4.4 ± 4.9 15.7 ± 19.8 0.04* 0.11 Average SaO2 93.4 ± 1.3 90.0 ± 3.6 0.01* 93.1 ± 2.4 90.3 ± 3.8 0.002* 0.40 Lowest SaO2 83.2 ± 5.0 75.0 ± 21.2 0.26 79.0 ± 6.1 77.8 ± 9.9 0.79 0.91 Supine % 44.5 ± 30.3 86.8 ± 20.4 <0.001 43.0 ± 35.6 66.2 ± 42.4 0.06 0.40 AHI: Apnea-Hypopnea Index; Apnea index: average number of apnea episodes per hour; CAI: Central Apnea Index: total number of central apneas per hour; CT90: cumulative percentage of total sleep time with oxygen desaturation below 90%; HI: Hypopnea index, average number of hypopnea episodes per hour; OAHI: Obstructive Apnea Hypopnea Index, total number of obstructive apneas and hypopneas per hour; OAI: Obstructive Apnea Index: total number of obstructive apneas divided sleep time; ODI: Oxygen Desaturation Index, number of events with oxygen desaturation below 4% threshold in one hour; SaO 2 : saturation of oxygen in hemoglobin. Additional Declarations Competing interest reported. Frances Chung holds the ResMed Research Chair of Anesthesia, sleep and perioperative medicine, consultant to Takeda Pharma. STOP-Bang questionnaire proprietary to University Health Network. Mandeep Singh (MS) currently holds the Canadian Anesthesiologists’ Society Career Scientist Grant and a Merit award from the Department of Anesthesiology and Pain Medicine, University of Toronto (Toronto, Canada) to support academic time. MS also serves on the Medical Advisory Board of Hypersomnia Foundation (Atlanta, GA) on a voluntary basis. Gincy A Lukachan, Azadeh Yadollahi, Dennis Auckley, Bojan Gavrilovic, John Matelski: No competing interests Supplementary Files Supplementarymaterial.docx Cite Share Download PDF Status: Published Journal Publication published 12 Jul, 2023 Read the published version in BMC Anesthesiology → Version 1 posted Editorial decision: Major revision 29 Mar, 2023 Reviews received at journal 27 Mar, 2023 Reviewers agreed at journal 05 Mar, 2023 Reviews received at journal 15 Feb, 2023 Reviewers agreed at journal 12 Feb, 2023 Reviewers invited by journal 26 Dec, 2022 Editor assigned by journal 26 Dec, 2022 Editor invited by journal 10 Dec, 2022 Submission checks completed at journal 10 Dec, 2022 First submitted to journal 16 Nov, 2022 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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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-2278755","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":158965900,"identity":"3400aeee-4e95-43c0-9f8e-9ab007dd7960","order_by":0,"name":"Gincy Ann Lukachan","email":"","orcid":"","institution":"Believers Church Medical College Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Gincy","middleName":"Ann","lastName":"Lukachan","suffix":""},{"id":158965901,"identity":"fb383f7a-4a86-41f1-953a-fd2a1aae860f","order_by":1,"name":"Azadeh Yadollahi","email":"","orcid":"","institution":"KITE - Toronto Rehabilitation Institute, University Health Network, University of Toronto;","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Azadeh","middleName":"","lastName":"Yadollahi","suffix":""},{"id":158965902,"identity":"5df29460-d05f-42e8-bdd9-3e3f1abe30de","order_by":2,"name":"Dennis Auckley","email":"","orcid":"","institution":"MetroHealth Medical Center, Case Western Reserve University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Dennis","middleName":"","lastName":"Auckley","suffix":""},{"id":158965903,"identity":"1dcf364a-16ee-4666-bffb-ebb3e2850533","order_by":3,"name":"Bojan Gavrilovic","email":"","orcid":"","institution":"KITE - Toronto Rehabilitation Institute, University Health Network, University of Toronto;","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Bojan","middleName":"","lastName":"Gavrilovic","suffix":""},{"id":158965904,"identity":"bafe86e7-6e63-47f6-9e76-334b560b1240","order_by":4,"name":"John Matelski","email":"","orcid":"","institution":"Biostatistics Research Unit, University Health Network, Toronto, Ontario, Canada","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"John","middleName":"","lastName":"Matelski","suffix":""},{"id":158965905,"identity":"4746ed6c-c347-4b54-84b5-4a6ff608374d","order_by":5,"name":"Frances Chung","email":"","orcid":"","institution":"Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto.","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Frances","middleName":"","lastName":"Chung","suffix":""},{"id":158965906,"identity":"b5f9bae7-6ef3-45a5-95da-6a8054377bf2","order_by":6,"name":"Mandeep Singh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5ElEQVRIiWNgGAWjYJACCTDJDEIVDAmkajlDkhaQLsY2IrTotp89eONDxR0G+Xbew68L5x3OM2dgfvgBnxazM3nJljPOPGMwOMyXZj1z2+FiywY2Ywm8Wg7kmEnzth1mMGDmMTPm3XY4ccMBHgb8Ws6/MZP+++8wg3wzSMscsBbmH3i13ADawthwmIHhMI/xY94GsBY2/LbceGNs2XPsGY/BYR4zZp5j6YkbDrOZWeB3WI7hjR81d+Tk+88Yf+apsU7ccLz58Q18WqAA6GUGBjZ4nBIDDoDV4o2OUTAKRsEoGLkAAPUFSv7+TGIHAAAAAElFTkSuQmCC","orcid":"","institution":"Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto.","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Mandeep","middleName":"","lastName":"Singh","suffix":""}],"badges":[],"createdAt":"2022-11-16 05:44:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2278755/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2278755/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12871-023-02193-y","type":"published","date":"2023-07-13T01:08:01+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":30270349,"identity":"8311677e-c77b-4aa6-8b67-fe061c550bff","added_by":"auto","created_at":"2022-12-13 16:27:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":27112,"visible":true,"origin":"","legend":"\u003cp\u003eParticipant flow in the study\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-2278755/v1/ccabcae66bf88170bd01a5e1.png"},{"id":30270352,"identity":"388a4d2a-b640-4a5d-9840-1635ff7769e4","added_by":"auto","created_at":"2022-12-13 16:27:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":190964,"visible":true,"origin":"","legend":"\u003cp\u003eA. The effect of semi-upright position on apnea-hypopnea index in the two groups per-protocol analysis.\u003c/p\u003e\n\u003cp\u003eB. The effect of semi-upright position on obstructive index in the two groups per-protocol analysis.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-2278755/v1/42b00c44d49eb7b9e2ee847a.png"},{"id":30270350,"identity":"685523fc-dcad-4567-85a4-0df7919f13ba","added_by":"auto","created_at":"2022-12-13 16:27:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":48079,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of semi-upright body position on the apnea-hypopnea index (AHI) in patients with supine-related OSA (n=10)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-2278755/v1/b0355c2efdd268333908a28d.png"},{"id":41737115,"identity":"0119fb6e-9a00-463d-bfea-51e7bb078eb6","added_by":"auto","created_at":"2023-08-18 04:15:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":793121,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2278755/v1/850ce127-aa00-4af3-9bdb-49caf6872d1e.pdf"},{"id":30271831,"identity":"f927661a-2836-4eb8-8daf-028ff3bac3c3","added_by":"auto","created_at":"2022-12-13 16:35:23","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":824479,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-2278755/v1/992af727d7d376ebfb3c9482.docx"}],"financialInterests":"Competing interest reported. Frances Chung holds the ResMed Research Chair of Anesthesia, sleep and perioperative medicine, consultant to Takeda Pharma. STOP-Bang questionnaire proprietary to University Health Network.\nMandeep Singh (MS) currently holds the Canadian Anesthesiologists’ Society Career Scientist Grant and a Merit award from the Department of Anesthesiology and Pain Medicine, University of Toronto (Toronto, Canada) to support academic time. MS also serves on the Medical Advisory Board of Hypersomnia Foundation (Atlanta, GA) on a voluntary basis. \nGincy A Lukachan, Azadeh Yadollahi, Dennis Auckley, Bojan Gavrilovic, John Matelski: No competing interests","formattedTitle":"The Impact of Semi-upright Position on Severity of Sleep Disordered Breathing in Patients with Obstructive Sleep Apnea: A two-arm, prospective, randomized controlled trial","fulltext":[{"header":"Introduction","content":"\u003cp\u003eObstructive sleep apnea (OSA) is a common sleep-related breathing disorder, associated with increased morbidity and mortality in the general and surgical population(1,2) in the perioperative period.(3) It is an independent risk-factor for post-operative cardiac and respiratory complications(4\u0026ndash;7) resulting in increased utilization of health care resources.(8)\u003c/p\u003e\n\u003cp\u003eThe screening and treatment of OSA is found to be cost effective on the lifetime horizon.(9) According to the current guidelines adult patients at risk of OSA should be screened preoperatively using validated tools such as STOP-Bang, P-SAP, Berlin, and ASA Check List.(10) The American Society of Anesthesiology (ASA) practice guidelines on the perioperative management of OSA advice to consider the initiation of continuous positive airway pressure (CPAP) therapy preoperatively in patients with newly detected severe OSA.(11)\u003csup\u003e,\u003c/sup\u003e Despite improvement in OSA severity and oxygenation with CPAP, poor patient compliance has been a hurdle to their use in the perioperative period.(12,13) Other alternatives to OSA treatment, such as weight reduction,(14) custom-made orthodontic appliances(15), and \u0026nbsp; surgery (orthodontic surgery,(16) uvulopalatopharyngeoplasty,(17) tonsillectomy,(18) or bariatric surgery(19)) are not feasible in the preoperative period. There is a need for alternative approaches for the management of OSA in surgical patients.\u003c/p\u003e\n\u003cp\u003ePositional therapy could be a useful intervention in surgical patients with OSA in the perioperative period.(20) This option may be more feasible in the postoperative setting as it is cost-effective, easy to administer, and can be adjusted to allow patient comfort. In the general population, sleeping in the non-supine and elevated posture was found to be effective in reducing OSA severity.(21\u0026ndash;23) The utility of positional therapy may be greater in patients with supine-related OSA. Supine-related OSA is defined as Apnea-hypopnea index (AHI) \u0026gt; 5 events/hr, and where the supine AHI was more than twice the AHI of the non-supine AHI, and the non-supine AHI was less than 5 events/hr.(24,25) \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe American Society of Anesthesiology practice guidelines on the perioperative management of OSA recognized that positional therapy may improve the AHI in patients with OSA, but acknowledged that the literature was \u0026ldquo;insufficient to evaluate the effects of positioning adult OSA patients in the postoperative setting\u0026rdquo;.(11) \u0026nbsp;We hypothesized that the use of a semi-upright position versus a supine position will prevent postoperative worsening of OSA in patients undergoing non-cardiac surgeries. The objective of the study was to determine whether a semi-upright versus supine position while asleep helps decrease the postoperative worsening of AHI in surgical patients with newly diagnosed OSA. The secondary objective was to study the impact of the semi-upright position in a subgroup of patients with supine-related OSA.\u003c/p\u003e"},{"header":"Methods","content":"\u003ch2\u003eStudy design\u003c/h2\u003e\n\u003cp\u003eThis was a two-arm, prospective, randomized controlled, proof of concept trial. The intervention was patient positioning in a semi-upright position (Group I: intervention, head-end elevation 30 to 45 degrees from horizontal), compared to supine position (Group C: control).\u003c/p\u003e\n\u003ch2\u003eStudy setting\u003c/h2\u003e\n\u003cp\u003eThis study was conducted at Toronto Western Hospital and Mount Sinai Hospital in Toronto, over a period of seven months. Institutional Review Board approval was obtained from both hospitals prior to start of this study (University Health Network 11-0056AE and Mount Sinai Hospital 11-0021-E). This trial was registered at www.clincialtrials.gov (NCT02152202). \u003c/p\u003e\n\u003cp\u003eThe inclusion criteria of patients were adult patients, American Society of Anesthesiologists (ASA) physical status I to IV, undergoing elective inpatient non-cardiac surgery with newly diagnosed OSA. The exclusion criteria were: patients with OSA on treatment (continuous positive airway pressure (CPAP), oral appliance, or previous OSA surgery); known cervical, shoulder, spine abnormalities, and/or chronic pain predisposing to difficulty in maintaining a sitting position and specific types of surgery, such as hip or spine, where a sitting position would be contraindicated postoperatively. Patients were screened by using the STOP-Bang questionnaire.(26) Patients identified as high risk of OSA (STOP-Bang score of three or greater) were consented to undergo a home portable polysomnography (PSG) and OSA status was confirmed by an AHI over 5 events per hour.\u003c/p\u003e\n\u003ch2\u003ePatient Recruitment, Intervention and Follow-up\u003c/h2\u003e\n\u003cp\u003ePortable PSG was performed using a 10-channel portable PSG device (Embletta X100; Embla, Broomfield, CO). The PSG was obtained preoperatively (preop) at home and on postoperatively (postop) on N 2. (27) The Embletta X100 is a level 2 diagnostic tool for OSA and has been validated against laboratory PSG.(28) The PSG recording montage comprised two electroencephalographic channels (C3 and C4), left or right electro-oculogram, chin muscle electromyogram, nasal cannula (pressure), thoracic and abdominal respiratory effort bands, body-position sensor, and pulse oximetry. At bedtime, the portable PSG device was connected to the patient by a PSG technician at their home. Patients were taught how to disconnect the device, which was picked up by the same sleep technician the following morning. The portable PSG recording was scored by a certified PSG technologist who was supervised by a sleep physician.\u003c/p\u003e\n\n\u003cp\u003eApneas were defined as a reduction in airflow from intranasal pressure of at least 90% for 10 seconds or longer, and hypopneas as reduction in flow of at least 30% for 10 seconds or longer, associated with \u0026ge; 4% oxygen desaturation.(29) Apneas and hypopneas were classified as either obstructive (presence of breathing effort) or central (absence of breathing effort) events. Mixed apneas were classified for events that began as central for at least 10 seconds and ended as obstructive, with a minimum of three obstructive efforts. AHI was the average number of apnea and hypopnea episodes per hour of recording. Apnea index was calculated as the average number of apnea episodes per hour. Hypopnea index was the average number of hypopnea episodes per hour. The secondary outcomes were obstructive apnea index (OAI), calculated as the total number of obstructive apneas divided total sleep time (TST); central apnea index (CAI) calculated as the total number of central apneas per hour; obstructive apnea hypopnea index (OAHI), calculated as the total number of obstructive apneas and hypopneas per hour; oxygen desaturation index (ODI), number of events with oxygen desaturation below 4% threshold per hour, and CT90, cumulative percentage of sleep duration with oxygen desaturation less than 90%.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003e Randomization and allocation concealment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePatients with OSA (defined as AHI \u0026gt; 5 events/hr), were randomized into two groups: Control or Intervention groups (computer generated blocks of 8) by the research analyst, who was not involved in group allocation or data collection during the study. Group allocation was concealed using sealed, opaque envelops, and patients were assigned to their group following surgery. In the Control group (Group C), there was no bed elevation, and patients were positioned at bedtime with no head elevation or bed angle to zero degrees from the horizontal. In the Intervention group (Group I), patients were positioned at bedtime in a semi-upright position with bed elevated to 30 to 45 degrees from horizontal. The bed angle was measured by a research assistant using an in-built bed angle monitor, or a goniometer, wherever applicable. The bed angle measurements were performed at night and in the morning to monitor compliance with the allocated bed position. Patients had the option to request changing the bed angle to facilitate recovery from surgery in view of pain and discomfort.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePerioperative anesthetic care and postoperative pain management\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA standardized balanced anesthetic technique was used in all patients per routine care. In general anesthesia (GA), patients received an induction dose of propofol, opioid (fentanyl and/or hydromorphone), an inhalational agent (sevoflurane or desflurane), and a muscle relaxant (rocuronium). The muscle relaxant was reversed with neostigmine and atropine. In regional anesthesia (RA), patients received spinal anesthetic and sedation using midazolam, fentanyl and a propofol infusion (20-150 mcg/kg/min). Use of intrathecal opioid (100 mcg preservative free morphine) was at the discretion of the anesthesiologist. Both groups received intravenous or oral narcotics in the postoperative period guided by the Acute Pain Service team, as per our institutional standard of care. Pain was evaluated on a score of 0\u0026ndash;10, with 0 as no pain and 10 as the most excruciating pain. Intravenous morphine by patient-controlled analgesia was initiated when the verbal pain score was 4 or higher. The research assistant visited patients daily to assist them with application and removal of the portable PSG, collect data, and document adverse events during the hospital stay.\u003c/p\u003e\n\u003ch2\u003eTarget sample size\u003c/h2\u003e\n\u003cp\u003eThe primary outcome of our study was AHI on postop N2. There was no previous research from the perioperative setting evaluating the impact of body positioning. Previous studies in the general population found that the mean change in AHI between the upright position (6 \u0026plusmn; 12 events/hr), and no head elevation (29 \u0026plusmn; 6 events/hr), respectively.(23,30) The original sample size calculated in the protocol was 28 in each arm calculated after taking a minimal clinically significant difference (MCSD) of an effect size (change in AHI) of at least 10 events per hour from baseline, a power of 0.9 and a standard deviation of 10, after adjusting for an estimated drop-out, and loss of follow up to a total of 20%. However, the study was terminated early due to concerns with funding, and a final sample size of 32 patients was obtained, which had sufficient power of 0.8, with type 1 error of 0.05. It was decided to proceed with analysis of the data by the senior authors. \u003c/p\u003e\n\n\u003ch2\u003eStatistical analysis\u003c/h2\u003e\n\u003cp\u003eAnalyses were performed using the SAS 9.2 statistical software for Windows (SAS Institute, Cary, NC) or R (version 3.1.1)(31). The analysis was blinded to allocation until the completion of data accrual period. Because of patient preference and deviation from assignment of intervention, a per-protocol analysis was performed for this study, where patients were analyzed based on the bed angle monitor reading noted in the morning following their PSG to show no deviation from protocol. An intention-to-treat analysis was performed as sensitivity analysis, meaning that all participants were analyzed in the group to which they were randomized.\u003c/p\u003e\n\u003cp\u003eBaseline demographic variables are summarized for the entire study population and by treatment group using standard bivariate methods, as implemented in R package tableone(32). For each variable we include a standardized mean difference, along with a p-value against the null hypothesis of equality between groups.\u003c/p\u003e\n\u003cp\u003eContinuous variables were compared using two-tailed, paired t-tests for variables with normally distributed data and Wilcoxon signed rank test for variables with non-normally distributed data.\u003c/p\u003e\n\n\u003cp\u003ePre-defined linear regression was performed for the primary and secondary outcomes, with preop AHI and supine-related OSA as covariates. Supine-related OSA was defined as AHI \u0026gt; 5 events/hr, and where the supine AHI was more than twice the AHI of the non-supine AHI, and the non-supine AHI was less than 5 events/hr. (24) A two-sided p value \u0026lt; 0.05 was considered significant and controlled for repeated observations, wherever applicable. \u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eStudy population \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePatient recruitment and flow is summarized in Figure 1, based on the CONSORT recommendations. A total of 635 patients were screened preoperatively, with 164 patients giving consent, of which 135 patients completed home PSG study. Eighty-three patients with OSA (AHI \u0026gt; 5 events/hr) were randomized, Group C: 41 and Group I: 42. During the study, six patients in Group C requested to change position to semi-upright position and were allocated to Group I. Complete postoperative N2 PSG data were obtained from 15 and 24 patients for Group C and I, respectively. This was partly because of patient refusal to undergo the PSG postoperatively while recovering from surgery, primarily due to postoperative pain and discomfort. Four patients were excluded as they required oxygen supplementation. Per protocol analysis was done for 14 patients in Group C and 21 patients in Group I. The baseline characteristics for PP and ITT analysis are presented in Table 1, and supplementary table 1, respectively. While randomization led to a more balanced distribution of baseline demographic variables, deviation of protocol resulted in disturbances for the PP analysis where control group had higher neck circumference and lower OAI and CT 90 values (SMD\u0026gt;0.8). The preop PSG (Table 1) data showed no difference in AHI, OAHI, HI between Group C and Group I. The baseline OAI was significantly higher (11.7 \u0026plusmn; 9.2 vs. 6.0 \u0026plusmn; 3.6 events per hour; p=0.01) while CAI was significantly lower (0.7 \u0026plusmn; 1.4 vs 3.7 \u0026plusmn; 9.5; p=0.04) in Group I than Group C. The CT90 was significantly higher (3.8 (0.4 - 6.1) % vs. 0.7 (0.1 - 1.2) %; p=0.04) and the lowest SaO\u003csub\u003e2\u003c/sub\u003e was significantly lower (79.1 \u0026plusmn; 6.1% vs 83.2 \u0026plusmn; 5.0 %; p= 0.04) in Group I vs Group C.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e \u003cem\u003ePrimary outcome.\u003c/em\u003e\u003c/strong\u003e Comparing postop N2 vs preop baseline, the AHI increased in Group C while it decreased in Group I (Table 2). The differences were not significant within the groups or between groups. (Group C: postop AHI vs preop AHI: 28.4 \u0026plusmn; 28.1 vs 18.1 \u0026plusmn; 13.3 events/hr, p=0.33; Group I: postop AHI vs preop AHI: 20.8 \u0026plusmn; 23.8 vs 21.4 \u0026plusmn; 13.1; p=0.36); overall p = 0.15. (Fig. 2A)\u003c/p\u003e\n\u003cp\u003eComparing postop N2 vs preop parameters, the changes in OAI within the two groups were not significant but there was an overall significant change between the two groups (Group C vs Group I: postop AHI 16.6 \u0026plusmn; 19.0 vs 8.6 \u0026plusmn; 11.2 events/hr); (overall p = 0.01) (Fig. 2B). There were no significant differences in CAI, HI, OAHI within the two groups and between groups (Table 2).\u003c/p\u003e\n\u003cp\u003eAmong the oxygenation parameters, CT90 (Supplementary fig. 3) significantly increased postoperatively in both groups (Group C: postop CT90 vs preop : 4.4 \u0026plusmn; 4.9% vs 1.3 \u0026plusmn; 2.0% , p = 0.003; Group I: postop CT90 vs preop : 15.7 \u0026plusmn; 19.8% vs 4.4 \u0026plusmn; 4.9% ; p = 0.04), and the average SaO\u003csub\u003e2\u003c/sub\u003e were significantly decreased in the postoperative period for both groups (Group C: postop average SaO\u003csub\u003e2 \u003c/sub\u003evs preop : 90.0 \u0026plusmn; 3.6% vs 93.4 \u0026plusmn; 1.3% , p=0.01; Group I: postop average SaO\u003csub\u003e2 \u003c/sub\u003evs preop : 90.3 \u0026plusmn; 3.8% vs 93.1 \u0026plusmn; 2.4% , p=0.002). However, between group comparison did not show a significant difference (Table 2). \u003c/p\u003e\n\u003cp\u003eThe other parameters were not significantly different from preop to postop and between the two groups (Table 2). \u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSubgroup analysis. \u003c/em\u003e\u003c/strong\u003eThe impact of body position was examined in patients classified as \u0026ldquo;supine-related OSA\u0026rdquo; (n=8; Group C: 5 patients, and Group I: 3 patients). There was greater reduction in mean AHI in Group I (postop AHI vs preop AHI: 6.0 \u0026plusmn; 3.0 vs 24.3 \u0026plusmn; 13.9 events/hr) than in Group C (Fig. 3), but the sample size was too small to evaluate statistical significance.\u003c/p\u003e\n"},{"header":"Discussion","content":"\u003cp\u003eThis is a novel study in the perioperative setting to evaluate the efficacy of semi-upright position postoperatively for management of newly diagnosed OSA. We found that it is feasible to institute positional therapy in the form of semi-upright position in the postoperative period for OSA patients. The elevated position resulted in a significant reduction in OAI by eight events per hour, but not the AHI, CAI, HI, and OAHI. The lack of positive results in AHI may be due to patients in the intervention group had significantly worse OAI, lower SaO\u003csub\u003e2, \u003c/sub\u003eand higher CT 90 preoperatively. Nevertheless, in the surgical patients with supine-related OSA, we were able to demonstrate the effectiveness of semi-upright position as the mean AHI decreased by 18 events per hour.\u003c/p\u003e\n\u003cp\u003eAlthough positive airway pressure (PAP) is the mainstay of treatment for moderate to severe OSA, perioperative adherence has been poor as studies have demonstrated only 34% CPAP adherence(13) and 45% auto-titrated CPAP adherence(33) in patients with newly diagnosed OSA treated with PAP therapy before surgery. This suggests a need for alternative therapies for these patients. We found that positional therapy is a feasible alternative treatment option for OSA patients in the perioperative setting especially in those with supine related OSA. These findings could be explained by the close association of upper airway collapsibility with body, head, and neck positioning.(24)\u003c/p\u003e\n\n\u003cp\u003ePrevious work has suggested that the semi-upright position significantly enlarges the upper airway dimensions.(34)\u003csup\u003e,\u003c/sup\u003e(35) The mean upper airway volume was greater with 44\u0026deg; head elevation compared to supine position.(35) Mild elevations of the head of the bed by 7.5\u0026deg; were associated with reductions in the AHI and improvements in oxygen parameters.(36) In a randomized crossover study of 30 postpartum women with OSA in the post-anesthesia care unit, 45\u0026deg; elevation of the upper body caused a significant reduction in AHI compared to non-elevated position.(37) A recently published randomized crossover trial among perioperative patients with moderate to severe OSA, compared high-flow nasal cannula (20 l/min with 40% oxygen concentration) with or without 30-degree head-of-bed elevation.(38) Patients were assessed with modified apnea hypopnea index, based exclusively on the airflow signal without arterial oxygen saturation criteria. High-flow nasal cannula caused significant improvement in OSA independently, with an additive effect when combined with 30-degree head-of-bed elevation (compared to Control flow-based AHI reduced by 10.9 (95% CI, 1 to 21) events \u0026middot; h\u0026ndash;1, P = 0.028; and 23 (95% CI, 13 to 32) events \u0026middot; h\u0026ndash;1, P \u0026lt; 0.001 respectively).\u003c/p\u003e\n\u003cp\u003eBody position may affect factors such as upper-airway passive collapsibility, airway dilator muscle activity, loop gain, and arousal threshold in patients with OSA.(39) These factors may play a role in how elevating th upper body can reduce OSA severity. In patients with OSA, pharyngeal critical closing pressure is higher in the supine position than lateral position.(40) which may be related to reduction in functional residual capacity.(41) An increase in the diaphragmatic descent during the respiratory cycle leads to an increase in lung volume and thus an increase in longitudinal traction on the upper airway which increase upper airway caliber during sleep and anesthesia.(42\u0026ndash;44) In addition, rostral fluid shift may worsen OSA severity and thus consolidate the effects of gravity on the propensity of OSA as demonstrated in healthy men(45)\u003csup\u003e,\u003c/sup\u003e(46) and non-obese men.(47) \u003c/p\u003e\n\n\u003cp\u003eA retrospective study on OSA patients with upper airway surgery found that the prevalence of positional OSA increased from 26 to 54% in those with persistent OSA at six months.(48) Among the non-responders to OSA surgery, almost 70% of patients were position dependent on preoperative PSG with no improvement at six months postoperatively.(49) This highlights the need to explore positional therapy, especially in those with positional OSA. \u003cbr\u003e \u003c/p\u003e\n\u003cp\u003eIn a systematic review of positional therapy for OSA, CPAP was better than positional therapy to lower the AHI, while positional therapy was better than inactive controls to lower the AHI and improved daytime sleepiness.(50) Long term compliance and treatment benefit from positional therapy needs to be determined by longitudinal studies, and compared to other modalities such as CPAP.\u003c/p\u003e\n\n\u003cp\u003eIn the general population, patients with supine-related OSA may be a suitable phenotype to benefit from positional therapy.(24) Good initial control of the OSA severity has been demonstrated but there is a lack of long-term compliance and outcome data.(24) The supine-related OSA phenotype can be easily identified on the preoperative sleep study. Though our data was limited, we found that patients with supine-related OSA benefit from postoperative semi-upright position with a reduction in AHI. Thus, we recommend the incorporation of semi-upright positioning as a practical adjunct to the perioperative management of OSA patients. It would be useful in those at high risk of OSA, newly diagnosed OSA or CPAP nonadherent patients. Further studies on custom-made pillows (to allow for elevated head position, or lateral position), tennis ball t-shirt,(21) or body position alarm devices (51) need to be done.\u003c/p\u003e\n\n\u003cp\u003eThere are several limitations to our study. First, our study had a small sample size with limited numbers in patients with supine-related OSA. Second, there can be variability in how the body position is reported and scored on the PSG. We used an accelerometer attached to the portable PSG which was placed on the patient\u0026prime;s chest. In-built automatic position sensors define body position as a categorical variable rather than a continuous variable, and may not reflect the physiological impact of various body positions on the collapsibility of the upper airway.(24) Third, head and neck position can independently influence the AHI.(52) Recording trunk position does not account for the effect of head and neck on upper-airway collapsibility and the impact on OSA severity.(53,54) However, we were able to show that the elevated position resulted in a significant reduction in OAI by eight events per hour. In those with supine-related OSA, we found a non-significant decrease in the mean AHI by 18 events per hour. \u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWe found that the semi-upright position compared to supine position reduced postoperative OAI, indicating reduction in upper airway collapsibility and obstructive apneas. There was a decreasing trend in postoperative AHI in patients with supine-related OSA. \u0026nbsp;Further studies on postoperative positional therapy are needed.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthics approval for this study was provided by Research Ethics Board at Toronto Western Hospital (Approval no. 14\u0026ndash;8710.0) and Mount Sinai Hospital (Approval no. 11-0021-E) on June 23, 2011 and June 22, 2011 respectively. The study was registered in clinicaltrials.gov NCT02152202 on 02/06/2014. The study was also done as per the declaration of Helsinki. The benefits and purposes of the study were explained to the patients, and each participant provided written, informed consent. Confidentiality was maintained at all levels of the study by avoiding identifiers and using codes to identify patients. Participants\u0026rsquo; involvement in the study was voluntary. Participants who did not wish to participate in the study or who wished to withdraw at any time were informed that they could do so without restriction.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eConsent for publication \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003e Availability of data and materials \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data and materials in this manuscript are available from the corresponding author on reasonable request.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCompeting interests \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFrances Chung holds the ResMed Research Chair of Anesthesia, sleep and perioperative medicine, consultant to Takeda Pharma. STOP-Bang questionnaire proprietary to University Health Network.\u003c/p\u003e\n\u003cp\u003eMandeep Singh (MS) currently holds the Canadian Anesthesiologists\u0026rsquo; Society Career Scientist Grant and a Merit award from the Department of Anesthesiology and Pain Medicine, University of Toronto (Toronto, Canada) to support academic time. MS also serves on the Medical Advisory Board of Hypersomnia Foundation (Atlanta, GA) on a voluntary basis. \u003c/p\u003e\n\u003cp\u003eGincy A Lukachan, Azadeh Yadollahi, Dennis Auckley, Bojan Gavrilovic, John Matelski: No competing interests\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by Departmental funds.\u003c/p\u003e\n\u003cp\u003eMandeep Singh is supported by a Canadian Anesthesiologists\u0026rsquo; Society Career Scientist Award and by the Merit Awards Program from the Department of\u003c/p\u003e\n\u003cp\u003eAnesthesiology and Pain Medicine at the University of Toronto.\u003c/p\u003e\n\u003cp\u003eFrances Chung reports having received research support from the University Health Network Foundation (Toronto, ON, Canada) and the Ontario Ministry of Health and Long-Term Care, royalties from UpToDate Inc., and consultant fees from the Takeda\u003c/p\u003e\n\u003cp\u003ePharmaceutical Company Limited. She is a developer of the STOP-Bang questionnaire (proprietary to the University Health Network).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFC and MS conceptualized the study, acquired funding, designed the methodology, supervised and oversaw the trial, assisted with writing the original draft, reviewed and edited the final manuscript. GAL, AY, DA and JM assisted with data analysis, drafting and revising the article. BG assisted with data collection, data analysis, drafting and revising the article. The author(s) read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003eFrances Chung and Mandeep Singh shared senior authorship for this study.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAcknowledgements \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe acknowledge the help of Islam Sazzadual, MSc, Babak Amirshahi, MD, Hoda Fazel MD and Hisham Elsaid MD for conduct of the study. We thank Pu Liao MD for database management, Yuming Sun, MD for scoring polysomnography. We acknowledge the help of Colin Shapiro MD for the supervision of polysomnography scoring. \u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAuthors and Affiliations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDepartment of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFrances Chung and Mandeep Singh\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDepartment of Anesthesia, Believers Church Medical College Hospital, Thiruvalla, Kerala, India\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGincy A Lukachan\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eKITE - Toronto Rehabilitation Institute, University Health Network, University of Toronto\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAzadeh Yadollahi and Bojan Gavrilovic\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDivision of Pulmonary, Critical Care and Sleep Medicine, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDennis Auckley\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBiostatistics Research Unit, University Health Network, Toronto, Ontario, Canada\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJohn Matelski\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorresponding author\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCorrespondence to Mandeep Singh.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eDur\u0026aacute;n J, Esnaola S, Rubio R, Iztueta \u0026Aacute;, Iztueta A, Iztueta \u0026Aacute;. Obstructive sleep apnea-hypopnea and related clinical features in a population-based sample of subjects aged 30 to 70 yr. American Journal of Respiratory and Critical Care Medicine. 2001 Mar;163(3 Pt 1):685\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eRedline S, Young T. Epidemiology and natural history of obstructive sleep apnea. Ear, Nose and Throat Journal. 1993;72(1):20\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eOpperer M, Cozowicz C, Bugada D, Mokhlesi B, Kaw R, Auckley D, et al. Does Obstructive Sleep Apnea Influence Perioperative Outcome? A Qualitative Systematic Review for the Society of Anesthesia and Sleep Medicine Task Force on Preoperative Preparation of Patients with Sleep-Disordered Breathing. Vol. 122, Anesthesia and Analgesia. 2016. p. 1321\u0026ndash;34.\u003c/li\u003e\n\u003cli\u003eHai F, Porhomayon J, Vermont L, Frydrych L, Jaoude P, El-Solh AA. Postoperative complications in patients with obstructive sleep apnea: A meta-analysis. 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Sleep \u0026amp; breathing = Schlaf \u0026amp; Atmung. 2011 Sep;15(3):367\u0026ndash;75.\u003c/li\u003e\n\u003cli\u003eIber C Cheeson A, Quan S.F. A israel S. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Techical Specifications.1st ed. Westchester, IL, USA: Amercan Academy of Sleep Medicine; 2007.\u003c/li\u003e\n\u003cli\u003eSkinner MA, Kingshott RN, Jones DR, Homan SDR, Taylor DR. Elevated posture for the management of obstructive sleep apnea. Sleep \u0026amp; Breathing. 2004;8(United States LG-English PT-Journal: Article EM-200507):193\u0026ndash;200.\u003c/li\u003e\n\u003cli\u003eRCoreTeam. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria; 2013.\u003c/li\u003e\n\u003cli\u003eYoshida Kazuki AB. tableone: Create \u0026ldquo;Table 1\u0026rdquo; to Describe Baseline Characteristics with or without Propensity Score Weights. R package version 0132. 2022;\u003c/li\u003e\n\u003cli\u003eLiao P, Luo Q, Elsaid H, Kang W, Shapiro CM, Chung F. Perioperative auto-titrated continuous positive airway pressure treatment in surgical patients with obstructive sleep apnea: A randomized controlled trial. Anesthesiology. 2013;119(4):837\u0026ndash;47.\u003c/li\u003e\n\u003cli\u003eBattagel J.M., Johal A., Smith A.M. et. al. Postural variation in oropharyngeal dimensions in subjects with sleep disordered breathing: a cephalometric study. Eur J Orthod. 2002;(24):263-276.\u003c/li\u003e\n\u003cli\u003eSouza FJF de B, Evangelista AR, Silva JV, P\u0026eacute;rico GV, Madeira K. Cervical computed tomography in patients with obstructive sleep apnea: influence of head elevation on the assessment of upper airway volume. Jornal Brasileiro de Pneumologia. 2016;42(1):55\u0026ndash;60.\u003c/li\u003e\n\u003cli\u003eSouza FJFB, Genta PR, de Souza Filho AJ, Wellman A, Lorenzi-Filho G. 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American journal of respiratory and critical care medicine. 2013 Oct;188(8):996\u0026ndash;1004.\u003c/li\u003e\n\u003cli\u003ePenzel T, M\u0026ouml;ller M, Becker HF, Knaack L, Peter JH. Effect of sleep position and sleep stage on the collapsibility of the upper airways in patients with sleep apnea. Sleep. 2001;24(1):90\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eJoosten SA, Sands SA, Edwards BA, Hamza K, Turton A, Lau KK, et al. Evaluation of the role of lung volume and airway size and shape in supine-predominant obstructive sleep apnoea patients. Respirology (Carlton, Vic). 2015 Jul;20(5):819\u0026ndash;27.\u003c/li\u003e\n\u003cli\u003eTagaito Y, Isono S, Tanaka A, Ishikawa T, Nishino T. Sitting posture decreases collapsibility of the passive pharynx in anesthetized paralyzed patients with obstructive sleep apnea. Anesthesiology. 2010;113(4):812\u0026ndash;8.\u003c/li\u003e\n\u003cli\u003eWalsh JH, Leigh MS, Paduch A, Maddison KJ, Armstrong JJ, Sampson DD, et al. 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Clinical Science. 2009;116(9):713\u0026ndash;20.\u003c/li\u003e\n\u003cli\u003eRedolfi S, Yumino D, Ruttanaumpawan P, Yau B, Su MCC, Lam J, et al. Relationship between Overnight Rostral Fluid Shift and Obstructive Sleep Apnea in Nonobese Men. American Journal of Respiratory and Critical Care Medicine. 2009;179(3):241\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eMart\u0026iacute;nez Ruiz de Apodaca P, Carrasco Llatas M, Matarredona Quiles S, Dalmau Galofre J. Development of positional obstructive sleep apnea (POSA) after upper airway surgery in OSA patients. Sleep and Breathing. 2020;24(3):849\u0026ndash;56.\u003c/li\u003e\n\u003cli\u003eLee YC, Eun YG, Shin SY, Kim SW. Change in position dependency in non-responders after multilevel surgery for obstructive sleep apnea: Analysis of polysomnographic parameters. European Archives of Oto-Rhino-Laryngology. 2014;271(5):1081\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eSrijithesh PR, Aghoram R, Goel A, Dhanya J. 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Influence of Head Extension, Flexion, and Rotation on Collapsibility of the Passive Upper Airway. Sleep. 2008;31(10):1440\u0026ndash;7. \u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1. Patient demographics across the two groups (Per-protocol).\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"661\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003eControl (n=14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003eIntervention (n=21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003eP value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003eStandardized Mean Difference\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge\u0026nbsp;\u003c/strong\u003e(years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e63\u0026plusmn;10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e65\u0026plusmn;12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.188\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBMI\u0026nbsp;\u003c/strong\u003e(kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e32.8\u0026plusmn;4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e35.2\u0026plusmn;7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.420\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eNeck Circumference\u0026nbsp;\u003c/strong\u003e(cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e43.3\u0026plusmn;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e41.0\u0026plusmn;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.752\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eGender F/M\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e5/9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e14/7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.651\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSTOP-Bang score\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e4.5\u0026plusmn;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e4.5\u0026plusmn;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.020\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eCo-morbidity\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eHypertension\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.144\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eGastroesophageal reflux\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.459\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eDiabetes Mellitus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.583\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eSmoker\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.147\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eAsthma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.232\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eCOPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.101\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eCAD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.739\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eType of surgery\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.707\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Orthopedic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; General\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Gynecology\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Urology\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eType of Anesthesia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.048\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; General\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Spinal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u003cstrong\u003eASA Status\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.589\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;II\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;III\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" width=\"100%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal amount of opioids (in mg IV morphine equivalents)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e1\u003csup\u003est\u003c/sup\u003e 24 h\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e10.3 [5.3 - 19.8]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e11.0 [5. - 20]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.080\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e1\u003csup\u003est\u003c/sup\u003e 48 h\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e21.4 [13.3 \u0026ndash; 44.4]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e33.4 [15.0 - 55.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.186\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003e1\u003csup\u003est\u003c/sup\u003e 72 h\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e25.8 [14.2 - 60.50]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e41.4 [25.0 - 81.5]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.259\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" width=\"100%\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Preoperative sleep study data between the two groups\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eAHI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e18.1 \u0026plusmn; 13.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e21.4 \u0026plusmn; 13.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.246\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eOAI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e6.1 \u0026plusmn; 3.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e11.7 \u0026plusmn; 9.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.807\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eOAHI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e14.6 \u0026plusmn; 7.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e20.7 \u0026plusmn; 12.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.593\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eCAI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e3.7 \u0026plusmn; 9.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e0.7 \u0026plusmn; 1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.444\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eHI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e8.6 \u0026plusmn; 5.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e9.0 \u0026plusmn; 7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eODI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e15.5 [13.5 - 23.7]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e17.9 [12.1 - 39.1]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.281\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eCT90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e0.7 [0.1 - 1.2]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e3.8 [0.4 \u0026ndash; 6.1]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.804\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eAverage SaO2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e93.4 \u0026plusmn; 1.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e93.1 \u0026plusmn; 2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.137\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"27.12121212121212%\"\u003e\n \u003cp\u003eLowest SaO2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e83.2 \u0026plusmn; 5.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"20%\"\u003e\n \u003cp\u003e79.1 \u0026plusmn; 6.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.242424242424242%\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.636363636363637%\"\u003e\n \u003cp\u003e0.748\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eData are expressed as mean (SD) or median (interquartile range IQR) where appropriate. Standardized Mean Difference was calculated using R package tableone\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBMI - body mass index; COPD \u0026ndash; chronic obstructive pulmonary disease; CAD \u0026ndash; coronary artery disease; OR \u0026ndash; operating room; h: hours.\u003c/p\u003e\n\u003cp\u003eAHI: Apnea-Hypopnea Index; Apnea index: average number of apnea episodes per hour;\u0026nbsp;Arousal \\index: number of arousals \u0026times; 60 / Total sleep time; CAI: Central Apnea Index: total number of central apneas per hour; CT90: cumulative percentage of Total sleep time with oxygen desaturation below 90%;\u0026nbsp;HI: Hypopnea index, average number of hypopnea episodes per hour;\u0026nbsp;OAHI: Obstructive Apnea Hypopnea Index, total number of obstructive apneas and hypopneas per hour; OAI: Obstructive Apnea Index: total number of obstructive apneas divided by Total sleep time; ODI: Oxygen Desaturation Index, number of events with oxygen desaturation below 4% threshold in one hour; REM%: Time spent in rapid eye movement stage of sleep; SaO\u003csub\u003e2\u003c/sub\u003e: saturation of oxygen in hemoglobin\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2: Postoperative sleep-related outcomes in both groups\u0026nbsp;\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"671\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"13.73134328358209%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" width=\"33.73134328358209%\"\u003e\n \u003cp\u003eControl (n = 14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" width=\"33.88059701492537%\"\u003e\n \u003cp\u003eIntervention (n = 21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.65671641791045%\"\u003e\n \u003cp\u003eBetween group comparison (ANCOVA)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"13.75186846038864%\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariable\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.210762331838565%\"\u003e\n \u003cp\u003ePre-op\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.004484304932735%\"\u003e\n \u003cp\u003ePost-op\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.10762331838565%\"\u003e\n \u003cp\u003ePre-op\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.406576980568012%\"\u003e\n \u003cp\u003ePost-op\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.684603886397607%\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"13.75186846038864%\"\u003e\n \u003cp\u003eAHI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.210762331838565%\"\u003e\n \u003cp\u003e18.1\u0026nbsp;\u0026plusmn;\u0026nbsp;13.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.004484304932735%\"\u003e\n \u003cp\u003e28.4\u0026nbsp;\u0026plusmn;\u0026nbsp;28.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.10762331838565%\"\u003e\n \u003cp\u003e21.4\u0026nbsp;\u0026plusmn;\u0026nbsp;13.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.406576980568012%\"\u003e\n \u003cp\u003e20.8\u0026nbsp;\u0026plusmn;\u0026nbsp;23.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.684603886397607%\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"13.75186846038864%\"\u003e\n \u003cp\u003eOAI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.210762331838565%\"\u003e\n \u003cp\u003e6.0\u0026nbsp;\u0026plusmn;\u0026nbsp;3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.004484304932735%\"\u003e\n \u003cp\u003e16.6\u0026nbsp;\u0026plusmn;\u0026nbsp;19.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.10762331838565%\"\u003e\n \u003cp\u003e11.7\u0026nbsp;\u0026plusmn;\u0026nbsp;9.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.406576980568012%\"\u003e\n \u003cp\u003e8.6\u0026nbsp;\u0026plusmn;\u0026nbsp;11.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.684603886397607%\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.01*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"13.75186846038864%\"\u003e\n \u003cp\u003eCAI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.210762331838565%\"\u003e\n \u003cp\u003e3.7\u0026nbsp;\u0026plusmn;\u0026nbsp;9.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.004484304932735%\"\u003e\n \u003cp\u003e3.6\u0026nbsp;\u0026plusmn;\u0026nbsp;4.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.10762331838565%\"\u003e\n \u003cp\u003e0.7\u0026nbsp;\u0026plusmn;\u0026nbsp;1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.406576980568012%\"\u003e\n \u003cp\u003e1.3\u0026nbsp;\u0026plusmn;\u0026nbsp;3.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.684603886397607%\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"13.75186846038864%\"\u003e\n \u003cp\u003eHI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.210762331838565%\"\u003e\n \u003cp\u003e8.6\u0026nbsp;\u0026plusmn;\u0026nbsp;5.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.004484304932735%\"\u003e\n \u003cp\u003e8.6\u0026nbsp;\u0026plusmn;\u0026nbsp;8.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.10762331838565%\"\u003e\n 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\u003ctd valign=\"top\" width=\"13.75186846038864%\"\u003e\n \u003cp\u003eAverage SaO2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.210762331838565%\"\u003e\n \u003cp\u003e93.4\u0026nbsp;\u0026plusmn;\u0026nbsp;1.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.004484304932735%\"\u003e\n \u003cp\u003e90.0\u0026nbsp;\u0026plusmn;\u0026nbsp;3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.01*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.10762331838565%\"\u003e\n \u003cp\u003e93.1\u0026nbsp;\u0026plusmn;\u0026nbsp;2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.406576980568012%\"\u003e\n \u003cp\u003e90.3\u0026nbsp;\u0026plusmn;\u0026nbsp;3.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.002*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.684603886397607%\"\u003e\n \u003cp\u003e0.40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"13.75186846038864%\"\u003e\n \u003cp\u003eLowest SaO2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.210762331838565%\"\u003e\n \u003cp\u003e83.2\u0026nbsp;\u0026plusmn;\u0026nbsp;5.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.004484304932735%\"\u003e\n \u003cp\u003e75.0\u0026nbsp;\u0026plusmn;\u0026nbsp;21.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.10762331838565%\"\u003e\n \u003cp\u003e79.0\u0026nbsp;\u0026plusmn;\u0026nbsp;6.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.406576980568012%\"\u003e\n \u003cp\u003e77.8\u0026nbsp;\u0026plusmn;\u0026nbsp;9.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.684603886397607%\"\u003e\n \u003cp\u003e0.91\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"13.75186846038864%\"\u003e\n \u003cp\u003eSupine %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.210762331838565%\"\u003e\n \u003cp\u003e44.5\u0026nbsp;\u0026plusmn;\u0026nbsp;30.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.004484304932735%\"\u003e\n \u003cp\u003e86.8\u0026nbsp;\u0026plusmn;\u0026nbsp;20.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.10762331838565%\"\u003e\n \u003cp\u003e43.0\u0026nbsp;\u0026plusmn;\u0026nbsp;35.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.406576980568012%\"\u003e\n \u003cp\u003e66.2\u0026nbsp;\u0026plusmn;\u0026nbsp;42.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"9.417040358744394%\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"18.684603886397607%\"\u003e\n \u003cp\u003e0.40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAHI: Apnea-Hypopnea Index; Apnea index: average number of apnea episodes per hour;\u0026nbsp;CAI: Central Apnea Index: total number of central apneas per hour; CT90: cumulative percentage of total sleep time with oxygen desaturation below 90%;\u0026nbsp;HI: Hypopnea index, average number of hypopnea episodes per hour;\u0026nbsp;OAHI: Obstructive Apnea Hypopnea Index, total number of obstructive apneas and hypopneas per hour; OAI: Obstructive Apnea Index: total number of obstructive apneas divided sleep time; ODI: Oxygen Desaturation Index, number of events with oxygen desaturation below 4% threshold in one hour; SaO\u003csub\u003e2\u003c/sub\u003e: saturation of oxygen in hemoglobin.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-anesthesiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bane","sideBox":"Learn more about [BMC Anesthesiology](http://bmcanesthesiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bane","title":"BMC Anesthesiology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Obstructive sleep apnea, supine-related OSA, surgery, elevated position, positional therapy","lastPublishedDoi":"10.21203/rs.3.rs-2278755/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2278755/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\u003eThe severity of sleep-disordered breathing is known to worsen postoperatively and is associated with increased cardio-pulmonary complications and increased resource implications. In the general population, the semi-upright position has been used in the management of OSA. We hypothesized that the use of a semi-upright position versus a non-elevated position will reduce postoperative worsening of OSA in patients undergoing non-cardiac surgeries\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was conducted as a prospective randomized controlled trial of perioperative\u003cstrong\u003e \u003c/strong\u003epatients, undergoing elective non-cardiac inpatient surgeries.\u003cstrong\u003e \u003c/strong\u003ePatients underwent a preoperative sleep study using a portable polysomnography device. Patients with OSA (apnea hypopnea index (AHI) \u0026gt;5 events/hr), underwent a sleep study on postoperative night 2 (N2) after being randomized into an intervention group (Group I): semi-upright position (30 to 45 degrees incline), or a control group (Group C) (zero degrees from horizontal). The primary outcome was postoperative AHI on N2. The secondary outcomes were obstructive apnea index (OAI), central apnea index (CAI), hypopnea index (HI), obstructive apnea hypopnea index (OAHI) and oxygenation parameters.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eThirty-five patients were included.\u003cstrong\u003e \u003c/strong\u003eTwenty\u003cstrong\u003e-\u003c/strong\u003eone patients were assigned to the Group 1 (females-14 (67%); mean age 65±12) while there were fourteen patients in the Group C (females-5 (36%); mean age 63±10). The semi-upright position resulted in a significant reduction in OAI in the intervention arm (Group C vs Group I postop AHI: 16.6 ± 19.0 vs 8.6 ± 11.2 events/hr; overall p = 0.01), but there were no significant differences in the overall AHI or other parameters between the two groups. Subgroup analysis of patients with “supine related OSA” revealed a decreasing trend in postoperative AHI with semi-upright position, but the sample size was too small to evaluate statistical significance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eIn patients with\u003cstrong\u003e \u003c/strong\u003enewly diagnosed OSA, the semi-upright position resulted in improvement in obstructive apneas, but not the overall AHI.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStudy registration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis trial was retrospectively registered in clinicaltrials.gov NCT02152202 on 02/06/2014.\u003c/p\u003e","manuscriptTitle":"The Impact of Semi-upright Position on Severity of Sleep Disordered Breathing in Patients with Obstructive Sleep Apnea: A two-arm, prospective, randomized controlled trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-12-13 16:27:18","doi":"10.21203/rs.3.rs-2278755/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2023-03-29T08:11:42+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2023-03-27T08:34:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"61481307-752a-4c82-b015-ba4b728dfa2f","date":"2023-03-05T19:37:06+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2023-02-15T12:42:50+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"c759cb60-170f-419c-8dcf-854111c561b1","date":"2023-02-12T13:35:47+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2022-12-26T14:22:31+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2022-12-26T13:50:34+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2022-12-10T07:50:13+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2022-12-10T07:33:32+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Anesthesiology","date":"2022-11-16T05:37:04+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-anesthesiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bane","sideBox":"Learn more about [BMC Anesthesiology](http://bmcanesthesiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bane","title":"BMC Anesthesiology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"bba85aa7-7523-41a1-a32e-cd203d3b9337","owner":[],"postedDate":"December 13th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2023-08-18T04:09:15+00:00","versionOfRecord":{"articleIdentity":"rs-2278755","link":"https://doi.org/10.1186/s12871-023-02193-y","journal":{"identity":"bmc-anesthesiology","isVorOnly":false,"title":"BMC Anesthesiology"},"publishedOn":"2023-07-13 01:08:01","publishedOnDateReadable":"July 13th, 2023"},"versionCreatedAt":"2022-12-13 16:27:18","video":"","vorDoi":"10.1186/s12871-023-02193-y","vorDoiUrl":"https://doi.org/10.1186/s12871-023-02193-y","workflowStages":[]},"version":"v1","identity":"rs-2278755","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2278755","identity":"rs-2278755","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}