High-flow nasal oxygenation versus standard face mask preoxygenation in patients with class 3 obesity: a prospective comparative study

High-flow nasal oxygenation versus standard face mask preoxygenation in patients with class 3 obesity: a prospective comparative study | 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 High-flow nasal oxygenation versus standard face mask preoxygenation in patients with class 3 obesity: a prospective comparative study Andrii Borysenko, Yurii Kuchyn, Kateryna Bielka, Dmytro Sazhyn, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8566628/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose The purpose of this study was to compare the effectiveness of high-flow nasal oxygenation (HFNO) with standard face-mask preoxygenation in patients with class 3 obesity undergoing induction of general anesthesia. We aimed to determine whether HFNO reduces the frequency of minor airway adverse events, improves oxygenation stability, prolongs safe apnea time, and decreases the need for airway adjuncts. Secondary objectives included evaluating minimal SpO₂, EtCO₂ changes, desaturation time, and identifying patient-related predictors of peri-intubation complications. The study sought to clarify the clinical value of HFNO for airway safety in this high-risk population. Methods: This prospective study included 40 adult patients with BMI > 40 kg/m² undergoing elective general surgery under general anesthesia. Patients were randomized into two equal groups: standard face mask preoxygenation (10–12 L/min, FiO₂ 1.0) or high-flow nasal oxygenation (60 L/min, FiO₂ 1.0). Preoxygenation time was standardized to 3 minutes. SpO₂ and EtCO₂ were measured before induction, during intubation, and after endotracheal tube placement. Primary endpoint: composite frequency of minor adverse events (desaturation 40 mmHg, adjunct device use, inadequate mask ventilation). Secondary endpoints included minimal SpO₂, time to desaturation < 92%, and correlations with anthropometric parameters. Results: Critical incidents occurred in 75% of patients. HFNO significantly reduced minor adverse events frequency (50% vs 100%, p = 0.002). Hypercapnia was the most common component (70% overall), more frequent in control (85%) than HFNO (55%, p = 0.021). HFNO improved minimal SpO₂ (91.2% ± 1.0 vs 87.5% ± 1.8, p = 0.034) and extended time to desaturation < 92% (189.4 ± 32.1 s vs 121.6 ± 27.8 s, p 150 s were independent predictors of incidents. Conclusions: HFNO significantly improves oxygenation stability, reduces minor events frequency, and prolongs safe apnea time in patients with class 3 obesity. It may be recommended as a preferred preoxygenation technique in this high-risk population. High-flow nasal oxygenation morbid obesity airway management preoxygenation desaturation anesthesia Figures Figure 1 Figure 2 Figure 3 Introduction Morbid obesity poses significant challenges for anesthetic management, particularly during airway control and induction of general anesthesia[ 1 – 4 ]. Reduced functional residual capacity, increased oxygen consumption, impaired chest wall mechanics, and higher rates of difficult mask ventilation and tracheal intubation lead to a markedly shortened safe apnea time in this population. As a result, even brief periods of apnea may result in rapid and profound arterial desaturation, increasing the risk of hypoxemia, cardiovascular instability, and peri-intubation complications[ 1 , 2 , 5 ]. Preoxygenation is a critical step in preparing patients with class 3 obesity for induction of anesthesia. The traditional method: tight-fitting face mask with 100% oxygen- remains the most widely practiced approach[ 3 , 6 – 8 ]. However, its effectiveness is highly dependent on a proper mask seal and patient compliance[ 9 ]. In individuals with a large neck circumference, reduced mandibular mobility, or high Mallampati grade, achieving an adequate seal may be challenging, reducing the efficiency of oxygen washout from the functional residual capacity[ 10 – 12 ]. Furthermore, standard face-mask preoxygenation does not provide apneic oxygenation once induction has begun, which further limits its ability to prolong safe apnea time. High-flow nasal oxygenation (HFNO) has emerged as an alternative method capable of delivering warmed and humidified oxygen at high flow rates, generating low-level positive airway pressure and promoting continuous oxygenation throughout the apneic phase[ 12 – 14 ]. These physiological advantages have led to growing interest in HFNO as a strategy to improve peri-intubation safety[ 15 ]. Several studies suggest that HFNO may extend safe apnea time, reduce desaturation events, and decrease the need for airway adjuncts in high-risk patients[ 6 , 15 – 18 ]. Nevertheless, clinical evidence in morbidly obese individuals remains limited, and findings are not entirely consistent across institutions and patient groups. Given the increasing prevalence of morbid obesity and the corresponding rise in high-risk anesthetic procedures, there is a practical need to clarify whether HFNO provides measurable advantages over conventional preoxygenation methods in this population. The current study aims to compare the effectiveness of HFNO and standard face-mask preoxygenation in patients with class 3 obesity undergoing elective general surgery. The primary objective was to evaluate the frequency of minor adverse events during induction of anesthesia. Secondary objectives included assessing minimal oxygen saturation, time to desaturation, end-tidal CO₂ changes, and the need for airway adjuncts. Materials and Methods The study included 40 patients with body mass index above 40 kg/m² who met the criteria of morbid obesity. During 2024–2025, at the Shalimov`s National Institute of Surgery and Transplantology, Kyiv, they underwent planned general surgical operations under general anesthesia with tracheal intubation. The patients were divided into two groups according to the method of preoxygenation. In the control group (n = 20), preoxygenation was performed via face mask with bag at an oxygen flow of 10–12 L/min and FiO₂ 1.0. In the study group (n = 20), high-flow nasal oxygenation was used with flow rate 60 L/min and FiO₂ 1.0. The preoxygenation time was three minutes in both groups. SpO₂ and EtCO₂ values were recorded before induction, during intubation and after endotracheal tube placement. We also assessed the induction time, frequency of minor adverse events were defined, and the use of airway adjuncts. Anthropometric parameters, Mallampati class, Cormack–Lehane grade, and the difficulty of mask ventilation were noted as well. A minor adverse events was defined as the occurrence of at least one of the following from the start of induction until intubation completion: desaturation (SpO₂ 40 mmHg), use of any adjunct device (videolaryngoscope, bougie, McCoy blade), more than one intubation attempt. For each case, type, duration and clinical conditions were recorded. Statistical analysis included descriptive statistics, t-test for independent samples, χ² test and logistic regression to evaluate associations between preoxygenation method and frequency of incidents. Results are presented as mean with standard deviation, and odds ratio (OR) with 95% confidence intervals. Differences were considered significant when p ≤ 0.05. The study followed the Declaration of Helsinki principles, and informed consent was obtained from all patients participated in the research. Ethical approval for this study was obtained from the Bioethics and Research Ethics Committee of Bogomolets National Medical University, Protocol No. 200, May 25, 2024. The CONSORT reporting guidelines applied to this study [ 19 ]. Results The analysis included 40 patients with class 3 obesity equally divided between the control group (face mask) and the study group (high-flow nasal oxygenation). Baseline parameters did not differ significantly: mean age was 53.2 (7.2) years, mean BMI 43.0 (3.0) kg/m², mean Mallampati class 2.2 (0.7), and mean induction time 147.5 (34.1)s (Table 1 ). Table 1 Airway assessment findings and induction-related categorical characteristics in the Mask and HFNC groups. Variable Mask mean(SD) HF mean(SD) Mask median[IQR] HF median[IQR] P value Age 54.9 (6.1) 51.5 (7.9) 58.0 [51.2–60.0] 53.0 [46.8–58.2] 0,169 Height 167.9 (7.6) 165.9 (6.4) 169.0 [163.5-171.8] 164.5 [161.8-169.2] 0,2959 Weight 121.0 (9.9) 118.4 (15.4) 120.0 [116.8–126.0] 113.0 [109.5-121.2] 0,1155 BMI 43.1 (1.9) 43.0 (3.8) 42.9 [41.4–44.4] 41.6 [41.0–43.0] 0,2079 Induction time (s) 143.5 (38.2) 151.5 (30.0) 150.0 [127.5–180.0] 150.0 [142.5–180.0] 0,5518 Lowest SpO2 (%) 89.9 (6.9) 96.0 (3.3) 91.5 [89.8–94.2] 96.5 [94.8–98.2] 0,0002 Time to desat (s) 54.0 (63.4) 13.0 (40.0) 20.0 [0.0-122.5] 0.0 [0.0–0.0] 0,0106 SpO2 preind (%) 97.9 (1.6) 97.2 (1.8) 98.0 [97.0–99.0] 98.0 [96.8–98.0] 0,2881 SpO2 preint (%) 91.5 (5.2) 97.5 (2.2) 92.5 [90.0–95.0] 98.0 [97.0–99.0] 0,0001 EtCO2 preint 35.3 (2.0) 36.4 (2.1) 36.0 [34.0–37.0] 36.5 [35.0–38.0] 0,115 Minor adverse events were observed in 30 patients (75%). Their frequency was significantly lower in the HFNO group − 10 cases (50%) compared to 20 (100%) in control (p = 0.002) (Table 2 ). Table 2 Physiological and procedural parameters during induction in the Mask and HFNC groups. Variable Mask n (%) HF n (%) p-value Sex Female: 12 (0.60), Male: 8 (0.40) Female: 14 (0.70), Male: 6 (0.30) 0.7411 Mallampati class 1: 3 (0.15), 2: 9 (0.45), 3: 8 (0.40), 4: 0 (0.00) 1: 3 (0.15), 2: 11 (0.55), 3: 5 (0.25), 4: 1 (0.05) 0.5951 Difficult intubation history No: 20 (1.00), Yes: 0 (0.00) No: 18 (0.90), Yes: 2 (0.10) 0.4872 Difficult bag-mask ventilation No: 20 (1.00) No: 20 (1.00) 1.0000 Cormack–Lehane I: 3 (0.15), II: 13 (0.65), III: 4 (0.20) I: 6 (0.30), II: 11 (0.55), III: 3 (0.15) 0.5196 Desaturation < 92% No: 10 (0.50), Yes: 10 (0.50) No: 18 (0.90), Yes: 2 (0.10) 0.0138 Induction complications No: 18 (0.90), Yes: 2 (0.10) No: 19 (0.95), Yes: 1 (0.05) 1.0000 Intubation technique Videolaryngoscope: 10 (0.50), Laryngoscope: 10 (0.50) Videolaryngoscope: 2 (0.10), Laryngoscope: 18 (0.90) 0.0138 Hypercapnia > 40 mmHg No: 3 (0.15), Yes: 17 (0.85) No: 9 (0.45), Yes: 11 (0.55) 0.0824 The main component of composite endpoint in both groups was hypercapnia after intubation (EtCO₂ >40 mmHg), seen in 70% of all patients, but more often in control (85%) than HFNO (55%; p = 0.021). Desaturation episodes below 92% were recorded in 12 patients (30.0% of total). In the control group the rate was 8 cases (40.0%), while in HFNO group only 4 (20.0%; p = 0.118). The mean minimal SpO₂ during induction was 89.3 ( 1.5)%, however patients who received HFNO had smaller fall in saturation (91.2 (1.0)%) than those with face mask (87.5 (1.8)%; p = 0.034). The average time to reach SpO₂ <92% after apnea was significantly longer in HFNO group: 189.4 ± 32.1 s compared to 121.6 ( 27.8) s in control (p < 0.001) (Fig. 1 ). Prolonged desaturation time in HFNO patients correlated with more stable EtCO₂ after intubation (r = − 0.41; p = 0.021), indicating more effective oxygen reserve maintenance during apnea. (Fig. 2 ) The strongest protective effect of HFNO was noted in patients with BMI ≥ 45 kg/m² and short neck, where standard mask preoxygenation was technically difficult. Also, the lowest desaturation values among all patients (down to 75% and 70%) were recorded only in the control group using face mask. Airway adjuncts were required in 10 patients (25.0%), mainly in control (8 cases − 40% vs 2–10% with HFNO; p = 0.041). Difficult mask ventilation was not registered. In subgroup analysis by anthropometric parameters, patients shorter than 160 cm had zero desaturation events with HFNO, while among those ≥ 170 cm the rate reached 20%. Mallampati class ≥ III was associated with higher incident frequency regardless of preoxygenation method (OR 4.96; 95% CI 1.05–23.5; p = 0.043) (Fig. 3 ). Induction longer than 150 s increased the risk of critical events (OR 2.87; p = 0.046). BMI ≥ 45 kg/m² did not affect total incident frequency (OR 0.80; p = 0.81), but correlated with more pronounced hypercapnia (mean EtCO₂ 45.1 (3.3) vs 42.7 (2.8) mmHg; p = 0.029). No significant relation was found for sex and age, although a slight tendency was seen for higher event frequency in males (OR 1.35; p = 0.70) and in patients older than 55 years (OR 3.05; p = 0.15) (Fig. 3 ). Conclusion HFNO demonstrated clear advantages over standard face-mask preoxygenation in patients with class 3 obesity. It significantly reduced the frequency of critical airway incidents, resulted in higher minimal SpO₂, and prolonged the time to desaturation during apnea. HFNO was associated with fewer adjunct interventions and more stable EtCO₂ profiles, particularly in patients with BMI ≥ 45 kg/m² or difficult airway predictors. These findings support the use of HFNO as a preferred preoxygenation method during induction of anesthesia in morbid obesity to enhance peri-intubation safety and reduce complication risk. Declarations Disclosures The authors declare that they have no conflicts of interest. Consent for publication Written informed consent for publication was obtained from all participants. Generative AI tools use The authors report having used ChatGPT for language editing. Funding statement None. Author Contribution All authors contributed to study design. Andrii Borysenko and Dmytro Sazhyn contributed to study conduct and data collection. Andrii Borysenko, Dmytro Sazhyn, Mykhailo Frank contributed to data analysis and data interpretation. Dmytro Sazhyn, Mykhailo Frank, Kateryna Bielka contributed to writing the manuscript. Yurii Kuchyn, Kateryna Bielka contributed to critical revision of the manuscript. Clinical trial registration : Bioethics and Research Ethics Committee of Bogomolets National Medical University Approval Decision, protocol #200 25\05\2024 via demand OSF Registered Trial. November 17. doi:10.17605/OSF.IO/9CY8T. First patient enrolment: 12\08\2024 Acknowledgements : The authors would like to thank the staff and administration of Shalimov’s Institute of Surgery and Transplantology, Kyiv, Ukraine, for their support and assistance during the conduct of this study. Data Availability The data that support the findings ofthis study are available on request from the corresponding author. References Seyni-Boureima R, Zhang Z, Antoine MMLK, Antoine-Frank CD. A review on the anesthetic management of obese patients undergoing surgery. BMC Anesthesiol. 2022;22:98. https://doi.org/10.1186/s12871-022-01579-8 . López T, Sastre JA, Gómez-Ríos MÁ. Airway Management in Obese Patients. In: Ahmad SI, editor. Obesity [Internet]. Cham: Springer International Publishing; 2024. pp. 121–39. [cited 2025 Apr 28]. https://doi.org/10.1007/978-3-031-62491-9_9 . Hardt K, Wappler F. Anesthesia for patients with class 3 obesity. Dtsch Ärztebl Int [Internet]. 2023. https://doi.org/10.3238/arztebl.m2023.0216 . 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09:05:51","extension":"html","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":70022,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8566628/v1/b40586ce75b571aef50165bb.html"},{"id":100594956,"identity":"1143baac-29f6-408e-bb41-5e8d091b7df9","added_by":"auto","created_at":"2026-01-19 13:46:40","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":41886,"visible":true,"origin":"","legend":"\u003cp\u003eTime to disaturation compared in both groups (sec)\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8566628/v1/e87a316a7022ffd0d6e7e203.jpg"},{"id":100565614,"identity":"60a21825-ce05-48d2-896b-6543fdad47a0","added_by":"auto","created_at":"2026-01-19 09:05:51","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":56480,"visible":true,"origin":"","legend":"\u003cp\u003ePost-intubation EtCO2 compared in both groups\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8566628/v1/b2fbedfd18ea9a0047f5ec86.jpg"},{"id":100595007,"identity":"9f8513ec-93db-46d0-9b5a-0f97da634d6e","added_by":"auto","created_at":"2026-01-19 13:46:58","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":60384,"visible":true,"origin":"","legend":"\u003cp\u003eMinor adverse events ration in both observed groups.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8566628/v1/aacc0495bc7246cd8776087c.jpg"},{"id":101645257,"identity":"bf8ce6cb-0110-4170-9cdc-e1b57af9cc51","added_by":"auto","created_at":"2026-02-02 08:28:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":744890,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8566628/v1/2e338ac2-be17-4230-badd-4ed86d90fa84.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"High-flow nasal oxygenation versus standard face mask preoxygenation in patients with class 3 obesity: a prospective comparative study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMorbid obesity poses significant challenges for anesthetic management, particularly during airway control and induction of general anesthesia[\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Reduced functional residual capacity, increased oxygen consumption, impaired chest wall mechanics, and higher rates of difficult mask ventilation and tracheal intubation lead to a markedly shortened safe apnea time in this population. As a result, even brief periods of apnea may result in rapid and profound arterial desaturation, increasing the risk of hypoxemia, cardiovascular instability, and peri-intubation complications[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePreoxygenation is a critical step in preparing patients with class 3 obesity for induction of anesthesia. The traditional method: tight-fitting face mask with 100% oxygen- remains the most widely practiced approach[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, its effectiveness is highly dependent on a proper mask seal and patient compliance[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In individuals with a large neck circumference, reduced mandibular mobility, or high Mallampati grade, achieving an adequate seal may be challenging, reducing the efficiency of oxygen washout from the functional residual capacity[\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Furthermore, standard face-mask preoxygenation does not provide apneic oxygenation once induction has begun, which further limits its ability to prolong safe apnea time.\u003c/p\u003e \u003cp\u003eHigh-flow nasal oxygenation (HFNO) has emerged as an alternative method capable of delivering warmed and humidified oxygen at high flow rates, generating low-level positive airway pressure and promoting continuous oxygenation throughout the apneic phase[\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. These physiological advantages have led to growing interest in HFNO as a strategy to improve peri-intubation safety[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Several studies suggest that HFNO may extend safe apnea time, reduce desaturation events, and decrease the need for airway adjuncts in high-risk patients[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan additionalcitationids=\"CR16 CR17\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Nevertheless, clinical evidence in morbidly obese individuals remains limited, and findings are not entirely consistent across institutions and patient groups.\u003c/p\u003e \u003cp\u003eGiven the increasing prevalence of morbid obesity and the corresponding rise in high-risk anesthetic procedures, there is a practical need to clarify whether HFNO provides measurable advantages over conventional preoxygenation methods in this population. The current study aims to compare the effectiveness of HFNO and standard face-mask preoxygenation in patients with class 3 obesity undergoing elective general surgery. The primary objective was to evaluate the frequency of minor adverse events during induction of anesthesia. Secondary objectives included assessing minimal oxygen saturation, time to desaturation, end-tidal CO₂ changes, and the need for airway adjuncts.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eThe study included 40 patients with body mass index above 40 kg/m\u0026sup2; who met the criteria of morbid obesity. During 2024\u0026ndash;2025, at the Shalimov`s National Institute of Surgery and Transplantology, Kyiv, they underwent planned general surgical operations under general anesthesia with tracheal intubation. The patients were divided into two groups according to the method of preoxygenation. In the control group (n\u0026thinsp;=\u0026thinsp;20), preoxygenation was performed via face mask with bag at an oxygen flow of 10\u0026ndash;12 L/min and FiO₂ 1.0. In the study group (n\u0026thinsp;=\u0026thinsp;20), high-flow nasal oxygenation was used with flow rate 60 L/min and FiO₂ 1.0. The preoxygenation time was three minutes in both groups.\u003c/p\u003e \u003cp\u003eSpO₂ and EtCO₂ values were recorded before induction, during intubation and after endotracheal tube placement. We also assessed the induction time, frequency of minor adverse events were defined, and the use of airway adjuncts. Anthropometric parameters, Mallampati class, Cormack\u0026ndash;Lehane grade, and the difficulty of mask ventilation were noted as well.\u003c/p\u003e \u003cp\u003eA minor adverse events was defined as the occurrence of at least one of the following from the start of induction until intubation completion: desaturation (SpO₂ \u0026lt;92%), hypercapnia after intubation (EtCO₂ \u0026gt;40 mmHg), use of any adjunct device (videolaryngoscope, bougie, McCoy blade), more than one intubation attempt. For each case, type, duration and clinical conditions were recorded.\u003c/p\u003e \u003cp\u003eStatistical analysis included descriptive statistics, t-test for independent samples, χ\u0026sup2; test and logistic regression to evaluate associations between preoxygenation method and frequency of incidents. Results are presented as mean with standard deviation, and odds ratio (OR) with 95% confidence intervals. Differences were considered significant when p\u0026thinsp;\u0026le;\u0026thinsp;0.05.\u003c/p\u003e \u003cp\u003eThe study followed the Declaration of Helsinki principles, and informed consent was obtained from all patients participated in the research. Ethical approval for this study was obtained from the Bioethics and Research Ethics Committee of Bogomolets National Medical University, Protocol No. 200, May 25, 2024. The CONSORT reporting guidelines applied to this study [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe analysis included 40 patients with class 3 obesity equally divided between the control group (face mask) and the study group (high-flow nasal oxygenation). Baseline parameters did not differ significantly: mean age was 53.2 (7.2) years, mean BMI 43.0 (3.0) kg/m\u0026sup2;, mean Mallampati class 2.2 (0.7), and mean induction time 147.5 (34.1)s (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAirway assessment findings and induction-related categorical characteristics in the Mask and HFNC groups.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMask mean(SD)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHF mean(SD)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMask median[IQR]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHF median[IQR]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e54.9 (6.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e51.5 (7.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e58.0 [51.2\u0026ndash;60.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e53.0 [46.8\u0026ndash;58.2]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,169\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e167.9 (7.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e165.9 (6.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e169.0 [163.5-171.8]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e164.5 [161.8-169.2]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,2959\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e121.0 (9.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e118.4 (15.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e120.0 [116.8\u0026ndash;126.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e113.0 [109.5-121.2]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,1155\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e43.1 (1.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e43.0 (3.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e42.9 [41.4\u0026ndash;44.4]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e41.6 [41.0\u0026ndash;43.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,2079\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInduction time (s)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e143.5 (38.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e151.5 (30.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e150.0 [127.5\u0026ndash;180.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e150.0 [142.5\u0026ndash;180.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,5518\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLowest SpO2 (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e89.9 (6.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e96.0 (3.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e91.5 [89.8\u0026ndash;94.2]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e96.5 [94.8\u0026ndash;98.2]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,0002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTime to desat (s)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e54.0 (63.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e13.0 (40.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20.0 [0.0-122.5]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0 [0.0\u0026ndash;0.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,0106\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpO2 preind (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e97.9 (1.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e97.2 (1.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e98.0 [97.0\u0026ndash;99.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e98.0 [96.8\u0026ndash;98.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,2881\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpO2 preint (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e91.5 (5.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e97.5 (2.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e92.5 [90.0\u0026ndash;95.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e98.0 [97.0\u0026ndash;99.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,0001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEtCO2 preint\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e35.3 (2.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e36.4 (2.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e36.0 [34.0\u0026ndash;37.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e36.5 [35.0\u0026ndash;38.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0,115\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eMinor adverse events were observed in 30 patients (75%). Their frequency was significantly lower in the HFNO group \u0026minus;\u0026thinsp;10 cases (50%) compared to 20 (100%) in control (p\u0026thinsp;=\u0026thinsp;0.002) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysiological and procedural parameters during induction in the Mask and HFNC groups.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMask n (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHF n (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSex\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFemale: 12 (0.60), Male: 8 (0.40)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFemale: 14 (0.70), Male: 6 (0.30)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.7411\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMallampati class\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1: 3 (0.15), 2: 9 (0.45), 3: 8 (0.40), 4: 0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1: 3 (0.15), 2: 11 (0.55), 3: 5 (0.25), 4: 1 (0.05)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.5951\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDifficult intubation history\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo: 20 (1.00), Yes: 0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo: 18 (0.90), Yes: 2 (0.10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.4872\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDifficult bag-mask ventilation\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo: 20 (1.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo: 20 (1.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.0000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCormack\u0026ndash;Lehane\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eI: 3 (0.15), II: 13 (0.65), III: 4 (0.20)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI: 6 (0.30), II: 11 (0.55), III: 3 (0.15)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.5196\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDesaturation\u0026thinsp;\u0026lt;\u0026thinsp;92%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo: 10 (0.50), Yes: 10 (0.50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo: 18 (0.90), Yes: 2 (0.10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.0138\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eInduction complications\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo: 18 (0.90), Yes: 2 (0.10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo: 19 (0.95), Yes: 1 (0.05)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.0000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIntubation technique\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVideolaryngoscope: 10 (0.50), Laryngoscope: 10 (0.50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVideolaryngoscope: 2 (0.10), Laryngoscope: 18 (0.90)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.0138\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHypercapnia\u0026thinsp;\u0026gt;\u0026thinsp;40 mmHg\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo: 3 (0.15), Yes: 17 (0.85)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo: 9 (0.45), Yes: 11 (0.55)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0824\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe main component of composite endpoint in both groups was hypercapnia after intubation (EtCO₂ \u0026gt;40 mmHg), seen in 70% of all patients, but more often in control (85%) than HFNO (55%; p\u0026thinsp;=\u0026thinsp;0.021).\u003c/p\u003e \u003cp\u003eDesaturation episodes below 92% were recorded in 12 patients (30.0% of total). In the control group the rate was 8 cases (40.0%), while in HFNO group only 4 (20.0%; p\u0026thinsp;=\u0026thinsp;0.118). The mean minimal SpO₂ during induction was 89.3 ( 1.5)%, however patients who received HFNO had smaller fall in saturation (91.2 (1.0)%) than those with face mask (87.5 (1.8)%; p\u0026thinsp;=\u0026thinsp;0.034). The average time to reach SpO₂ \u0026lt;92% after apnea was significantly longer in HFNO group: 189.4\u0026thinsp;\u0026plusmn;\u0026thinsp;32.1 s compared to 121.6 ( 27.8) s in control (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eProlonged desaturation time in HFNO patients correlated with more stable EtCO₂ after intubation (r = \u0026minus;\u0026thinsp;0.41; p\u0026thinsp;=\u0026thinsp;0.021), indicating more effective oxygen reserve maintenance during apnea. (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e ) The strongest protective effect of HFNO was noted in patients with BMI\u0026thinsp;\u0026ge;\u0026thinsp;45 kg/m\u0026sup2; and short neck, where standard mask preoxygenation was technically difficult. Also, the lowest desaturation values among all patients (down to 75% and 70%) were recorded only in the control group using face mask.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAirway adjuncts were required in 10 patients (25.0%), mainly in control (8 cases \u0026minus;\u0026thinsp;40% vs 2\u0026ndash;10% with HFNO; p\u0026thinsp;=\u0026thinsp;0.041). Difficult mask ventilation was not registered.\u003c/p\u003e \u003cp\u003eIn subgroup analysis by anthropometric parameters, patients shorter than 160 cm had zero desaturation events with HFNO, while among those\u0026thinsp;\u0026ge;\u0026thinsp;170 cm the rate reached 20%. Mallampati class\u0026thinsp;\u0026ge;\u0026thinsp;III was associated with higher incident frequency regardless of preoxygenation method (OR 4.96; 95% CI 1.05\u0026ndash;23.5; p\u0026thinsp;=\u0026thinsp;0.043) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Induction longer than 150 s increased the risk of critical events (OR 2.87; p\u0026thinsp;=\u0026thinsp;0.046).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBMI\u0026thinsp;\u0026ge;\u0026thinsp;45 kg/m\u0026sup2; did not affect total incident frequency (OR 0.80; p\u0026thinsp;=\u0026thinsp;0.81), but correlated with more pronounced hypercapnia (mean EtCO₂ 45.1 (3.3) vs 42.7 (2.8) mmHg; p\u0026thinsp;=\u0026thinsp;0.029). No significant relation was found for sex and age, although a slight tendency was seen for higher event frequency in males (OR 1.35; p\u0026thinsp;=\u0026thinsp;0.70) and in patients older than 55 years (OR 3.05; p\u0026thinsp;=\u0026thinsp;0.15) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eHFNO demonstrated clear advantages over standard face-mask preoxygenation in patients with class 3 obesity. It significantly reduced the frequency of critical airway incidents, resulted in higher minimal SpO₂, and prolonged the time to desaturation during apnea. HFNO was associated with fewer adjunct interventions and more stable EtCO₂ profiles, particularly in patients with BMI\u0026thinsp;\u0026ge;\u0026thinsp;45 kg/m\u0026sup2; or difficult airway predictors. These findings support the use of HFNO as a preferred preoxygenation method during induction of anesthesia in morbid obesity to enhance peri-intubation safety and reduce complication risk.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eDisclosures\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no conflicts of interest.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eWritten informed consent for publication was obtained from all participants.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eGenerative AI tools use\u003c/h2\u003e \u003cp\u003e The authors report having used ChatGPT for language editing.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding statement\u003c/h2\u003e \u003cp\u003eNone.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAll authors contributed to study design. Andrii Borysenko and Dmytro Sazhyn contributed to study conduct and data collection. Andrii Borysenko, Dmytro Sazhyn, Mykhailo Frank contributed to data analysis and data interpretation. Dmytro Sazhyn, Mykhailo Frank, Kateryna Bielka contributed to writing the manuscript. Yurii Kuchyn, Kateryna Bielka contributed to critical revision of the manuscript.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eClinical trial registration\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBioethics and Research Ethics Committee of Bogomolets National Medical University Approval Decision, protocol #200 25\\05\\2024 via demand\u003c/p\u003e\n\u003cp\u003eOSF Registered Trial. November 17. doi:10.17605/OSF.IO/9CY8T.\u003c/p\u003e\n\u003cp\u003eFirst patient enrolment: 12\\08\\2024\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eThe authors would like to thank the staff and administration of Shalimov’s Institute of Surgery and Transplantology, Kyiv, Ukraine, for their support and assistance during the conduct of this study.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data that support the findings ofthis study are available on request from the corresponding author.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSeyni-Boureima R, Zhang Z, Antoine MMLK, Antoine-Frank CD. A review on the anesthetic management of obese patients undergoing surgery. 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CONSORT 2010 Statement: updated guidelines for reporting parallel group randomised trials. CONSORT Group.; 2010.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"High-flow nasal oxygenation, morbid obesity, airway management, preoxygenation, desaturation, anesthesia","lastPublishedDoi":"10.21203/rs.3.rs-8566628/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8566628/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e \u003cp\u003eThe purpose of this study was to compare the effectiveness of high-flow nasal oxygenation (HFNO) with standard face-mask preoxygenation in patients with class 3 obesity undergoing induction of general anesthesia. We aimed to determine whether HFNO reduces the frequency of minor airway adverse events, improves oxygenation stability, prolongs safe apnea time, and decreases the need for airway adjuncts. Secondary objectives included evaluating minimal SpO₂, EtCO₂ changes, desaturation time, and identifying patient-related predictors of peri-intubation complications. The study sought to clarify the clinical value of HFNO for airway safety in this high-risk population.\u003c/p\u003e\u003ch2\u003eMethods:\u003c/h2\u003e \u003cp\u003eThis prospective study included 40 adult patients with BMI\u0026thinsp;\u0026gt;\u0026thinsp;40 kg/m\u0026sup2; undergoing elective general surgery under general anesthesia. Patients were randomized into two equal groups: standard face mask preoxygenation (10\u0026ndash;12 L/min, FiO₂ 1.0) or high-flow nasal oxygenation (60 L/min, FiO₂ 1.0). Preoxygenation time was standardized to 3 minutes. SpO₂ and EtCO₂ were measured before induction, during intubation, and after endotracheal tube placement. Primary endpoint: composite frequency of minor adverse events (desaturation\u0026thinsp;\u0026lt;\u0026thinsp;92%, hypercapnia\u0026thinsp;\u0026gt;\u0026thinsp;40 mmHg, adjunct device use, inadequate mask ventilation). Secondary endpoints included minimal SpO₂, time to desaturation\u0026thinsp;\u0026lt;\u0026thinsp;92%, and correlations with anthropometric parameters.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eCritical incidents occurred in 75% of patients. HFNO significantly reduced minor adverse events frequency (50% vs 100%, p\u0026thinsp;=\u0026thinsp;0.002). Hypercapnia was the most common component (70% overall), more frequent in control (85%) than HFNO (55%, p\u0026thinsp;=\u0026thinsp;0.021). HFNO improved minimal SpO₂ (91.2% \u0026plusmn; 1.0 vs 87.5% \u0026plusmn; 1.8, p\u0026thinsp;=\u0026thinsp;0.034) and extended time to desaturation\u0026thinsp;\u0026lt;\u0026thinsp;92% (189.4\u0026thinsp;\u0026plusmn;\u0026thinsp;32.1 s vs 121.6\u0026thinsp;\u0026plusmn;\u0026thinsp;27.8 s, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Requirement for airway adjuncts was higher in the control group (40% vs 10%, p\u0026thinsp;=\u0026thinsp;0.041). Mallampati\u0026thinsp;\u0026ge;\u0026thinsp;III and induction time\u0026thinsp;\u0026gt;\u0026thinsp;150 s were independent predictors of incidents.\u003c/p\u003e\u003ch2\u003eConclusions:\u003c/h2\u003e \u003cp\u003eHFNO significantly improves oxygenation stability, reduces minor events frequency, and prolongs safe apnea time in patients with class 3 obesity. It may be recommended as a preferred preoxygenation technique in this high-risk population.\u003c/p\u003e","manuscriptTitle":"High-flow nasal oxygenation versus standard face mask preoxygenation in patients with class 3 obesity: a prospective comparative study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-19 09:05:41","doi":"10.21203/rs.3.rs-8566628/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"fd0bbfaf-9876-4593-ab36-904eae8c3b14","owner":[],"postedDate":"January 19th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-02T08:25:26+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-19 09:05:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8566628","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8566628","identity":"rs-8566628","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}