The Impact of Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE) on Intragastric Pressure During Anaesthesia Induction in Overweight Patients: A Randomized Controlled Trial

The Impact of Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE) on Intragastric Pressure During Anaesthesia Induction in Overweight Patients: A 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 Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE) on Intragastric Pressure During Anaesthesia Induction in Overweight Patients: A Randomized Controlled Trial Chen Yating, Ying Hangbo, Tong Yao, Sun Huanhuan, Zhang Yijie, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6848070/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: Although many studies have shown that transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) can be used in anaesthesia induction, its specific effects on obese patients remain unknown. Methods: We recruited 135 patients (BMI ≥25 kg/m²) who were randomly assigned to three groups: the facemask ventilation group (M group), the THRIVE group (T group), and the facemask with no ventilation combined THRIVE group (M+T group). Before induction, all patients underwent preoxygenation with a facemask until the partial pressure of end-tidal oxygen (PEtO 2 ) exceeded 90%. After induction, a gastric intraluminal pressure catheter was inserted, and the catheter was connected to a disposable pressure transducer (in central venous pressure mode) via a three-way stopcock, with the calibration point located at the mid-axillary line. Subsequently, each group underwent different ventilation methods for 2 minutes before tracheal intubation and mechanical ventilation. Results: There were no significant differences in initial intragastric pressure among the three groups. However, the peak intragastric pressure in the T and M+T groups was significantly lower than that in the M group ( P < 0.05). Within-group comparisons indicated no statistically significant differences between initial and peak intragastric pressures in the T and M+T groups. In contrast, the peak intragastric pressure during ventilation in the M group was significantly higher than its initial value ( P < 0.05). Fewer patients in the T and M+T groups demonstrated notable changes in gastric antral area on ultrasound compared with the M group ( P < 0.05). Additionally, the lowest SpO 2 and PEtO 2 in the T and M+T groups were significantly higher than those in the M group ( P < 0.05). However, the first complete respiratory waveform of PEtCO 2 after mechanical ventilation and the lowest PEtCO 2 within 2 minutes of mechanical ventilation were higher in the T and M+T groups than in the M group ( P < 0.05). Conclusion: The use of THRIVE during the induction of anaesthesia in overweight patients, compared with conventional facemask preoxygenation, can improve oxygen saturation while ensuring minimal alterations in intragastric pressure. Trial registration: Chinese Clinical Trial Registry ChiCTR2300075652. Registered date: 12/09/2023 Obesity Anesthesia Induction THRIVE Intragastric Pressure Oxygenation Figures Figure 1 Figure 2 Introduction During anaesthesia induction, positive pressure ventilation masks are frequently utilized to prevent hypoxia. However, this method may cause gastric insufflation, thereby increasing the risks of reflux, aspiration, and postoperative nausea and vomiting. [ 1 ] Notably, aspiration is a significant cause of anaesthesia-related mortality. [ 2 ] While pressure-controlled mask ventilation with a pressure setting below 15 cmH₂O [ 3 ] can mitigate the risk of gastric insufflation, anaesthesiologists must maintain alertness, especially in high-risk populations such as overweight patients. Hashem et al [ 4 ] identified obesity as a strong independent risk factor for gastroesophageal reflux disease (GERD), with the probability being 2.5 times higher than that in the general population. Studies have shown that compared with normal individuals, obese patients are more prone to experiencing a decrease in lower esophageal sphincter (LES) pressure both after meals and during anaesthesia. [ 5 , 6 ] Therefore, we reasonably speculate that overweight patients are a key population at risk of gastric insufflation and reflux during anaesthesia induction. Moreover, a study in North America showed that when a patient's BMI is 30 kg m − 2 , their functional residual capacity (FRC) and expiratory reserve volume (ERV) are only 75% and 47%, respectively, of those of patients with a BMI of 20 kg m − 2 . [ 7 ] Other finding highlights that obesity impairs respiratory muscle function, increases oxygen consumption, reduces pulmonary compliance, and affects gas exchange, ultimately resulting in poor oxygenation. [ 8 – 10 ] Collectively, these findings suggest that overweight patients possess limited oxygen reserves and are predisposed to hypoxemia during the induction, as well as a higher risk of gastric insufflation and aspiration. It suggests that further optimisation of the method of oxygenation is required to minimise gastric insufflation during the induction of anaesthesia in overweight patients. Trans-nasal humidified rapid insufflation ventilatory exchange (THRIVE), also known as high-flow nasal cannula (HFNC) oxygen therapy, is a noninvasive oxygen therapy that directly delivers a specific concentration of high-flow air-oxygen mixed gas to the patient through heating and humidification. THRIVE enhances ventilation and oxygenation while reducing anatomical dead space in the upper airway and decreasing the work of breathing. This modality has been applied in pre-intubation preoxygenation, treatment of respiratory failure, respiratory support after major surgery, and oxygen therapy following extubation. [ 11 – 15 ] Research has shown that compared with conventional oxygenation, THRIVE provides a longer safe apnea time and higher minimum oxygen saturation in morbidly obese patients during anaesthesia induction. [ 16 ] We hypothesize that THRIVE can reduce changes in intragastric pressure while effectively ensuring oxygenation during the induction of general anaesthesia in overweight patients. Methods Study Design and Participants The study received approval from the Ethics Committee of the 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China, on 4 September 2023(KY2023-195), Chairperson Professor Zimiao Chen. And it was registered in the China Clinical Trial Registration Center (ChiCTR2300075652) before patient enrolment. All participants provided written informed consent upon enrollment in the study. This manuscript adheres to the Consolidated Standards of Reporting Trials (CONSORT) guidelines. Adult patients (18–65 years), ASA class I-II, BMI ≥ 25, requiring anaesthesia induction without special position requirements, were enrolled after written consent during pre-operative evaluation. Exclusion criteria were as follows: difficult airway; skull base fractures; active bleeding in the airway or upper digestive tract, or with esophageal varices; pregnancy; severe gastroesophageal reflux disease; neuromuscular disorders; ASA ≥ III. Randomization and Blinding Eligible patients were blindly and randomly assigned to three groups according to computer-generated random codes. These codes were kept in sealed opaque envelopes. A large sterile surgical towel was hung around the patient's neck to separate the surgeon and the anaesthesiologist using ultrasound on the other side, ensuring they were also unaware of the group assignments. The monitor screen was turned to the opposite side, and the data recorder faced away from the procedure to document the data, remaining unaware of the group assignments. Both the anaesthesiologist and the surgeon were blinded to the group allocation. Study protocol Patients who met the inclusion criteria were randomly assigned to three groups. The mask group (M group) received pressure-controlled ventilation via a face mask. The transnasal Humidified Rapid Insufflation Ventilatory Exchange group (T group) received oxygen via high-flow nasal cannula. The combined mask and THRIVE group (M + T group) received oxygen via high-flow nasal cannula with a face mask loosely applied over the mouth and nose. All patients were first preoxygenated with a tight-fitting facemask, which delivered 100% oxygen and a fresh gas flow of 8 L min − 1 to reach PEtO 2 > 90%, and ECG, NIBP, heart rate, and pulse oximetry monitoring were applied. Using propofol (1.5–2.5 mg kg − 1 ), sufentanil (0.2–0.4 µg kg − 1 ), and rocuronium bromide (0.3–0.6 mg kg − 1 ) for anaesthetic agents. If significant hemodynamic fluctuations occur during induction, appropriate vasopressors should be administered. After loss of consciousness (disappearance of eyelash reflex), a gastric pressure measurement tube was inserted orally into the stomach under the guidance of a video laryngoscope in all groups (insertion was confirmed by the aspiration of gastric fluid). The tube was then connected to a disposable pressure transducer that had been pre-set to measure central venous pressure and calibrated to the mid-axillary line. Subsequently, in the M group, patients were ventilated by the PCV mode in anaesthesia machine (Pinsp = 15 cmH 2 O, TV = 8 L min − 1 , RR = 12 breaths per min with 100% oxygen) via face mask. The T group received high-flow nasal cannula ventilation at a rate of 60 L min − 1 with 100% oxygen. Airway patency was maintained using a chin lift or jaw thrust. The M + T group used a ventilation mode like T group, while adding a loosely fitting face mask at the rate of 8 L min − 1 . After 2 minutes of apnoeic oxygenation, intubation or laryngeal mask airway was performed, and mechanical ventilation was initiated (TV = 6–8 l min − 1 , RR = 15, 100% oxygen flow rate of 1 l min − 1 , PEEP = 5) for 2 minutes. Then record monitoring data. (see Fig. 1 ) During the trial, the anaesthesiologist performed ultrasonographic measurements of the gastric antral area before and after ventilation. The calculation formula: CSAa (cm²) = π × anteroposterior diameter of the gastric antrum (cm) × craniocaudal diameter of the gastric antrum (cm) ÷ 4. Additionally, the surgeon graded gastric insufflation under direct laparoscopic visualization: Grade I, No Distension; Grade II, Mild Distension; Grade III, Moderate Distension that affects the surgical view but does not interfere with operation; Grade IV, Severe Distension that necessary measures should be taken, such as nasogastric tube or percutanaeous aspiration. The primary outcome was the incidence of increased intragastric pressure. The initial pressure measured upon insertion of the intragastric pressure catheter was recorded as P1. The highest-pressure during ventilation was recorded as P2. The pressure at the end of ventilation was recorded as P3. Cases with P3-P1 > 0 were defined as positive cases. The secondary outcomes included the grading of gastric insufflation, CSAa, SpO₂, PEtO₂, and PEtCO₂ levels at different time points (T1: before oxygenation; T2: after preoxygenation; T3: lowest value before mechanical ventilation; T4: first complete breath waveform after mechanical ventilation; T5: lowest value within 2 minutes of mechanical ventilation), and the incidence of adverse events. Sample size evaluation Based on the pilot study results, the mean differences in intragastric pressure for groups M, T, and M + T were 0.6 mmHg, 0.2 mmHg, and 0.2 mmHg, respectively, with standard deviations of 0.49 mmHg, 0.4 mmHg, and 0.4 mmHg. Using GPower 3.1 software, with a Type I error rate (α) of 0.05 and power (1 - β) of 0.90, the calculated sample size was 30 patients per group. Considering the difficulties in gastric intubation and potential data loss, we decided to include 135 patients. Statistical Methods Statistical analyses were performed using SPSS 25 software. Normally distributed continuous data were presented as mean ± standard deviation (SD). Repeated measures analysis of variance (ANOVA) was used for within-group comparisons, while one-way ANOVA was used for between-group comparisons. Post hoc comparisons were conducted using the LSD method. For non-normally distributed continuous data, the median (M) and interquartile range (IQR) were used, and within-group comparisons were performed using the Wilcoxon signed-rank test. Categorical data were expressed as frequency counts or percentages (%), and comparisons were made using the chi-square test. A P -value less than 0.05 was considered statistically significant. RESULTS Based on the inclusion and exclusion criteria, one hundred and thirty-five patients were enrolled between September, 2023, and January, 2024 at the 1 st Affiliated Hospital of Wenzhou Medical University. Two patients were excluded (Fig. 2). There were no significant differences between the three groups in terms of baseline characteristics (Table 1). Table 1-Baseline patient characteristics of three groups Group M (n=45) Group T (n=44) Group M+T (n=44) P value Age (y); x̄ ±s 44.6±10.1 44.5±10.4 44.1±11.8 0.979 Sex (male/ female) 18/27 15/29 16/28 0.844 BMI (kg.m 2 ); x̄ ±s 29.0±3.0 29.1±2.4 28.8±3.2 0.915 ASA (I/II) 6/39 6/38 5/39 0.942 Mallampatti class (I/II) 25/20 30/14 31/13 0.284 OSAS（0/1/2） 14/28/3 14/25/5 19/19/6 0.434 BP（mmHg） SBP 146.6±18.9 147.4±18.4 141.2±20.9 0.265 DBP 82.9±13.3 84.5±10.6 80.6±12.6 0.377 Heart Rate（bpm） 75.9±15.0 74.3±12.8 72.2±10.9 0.412 Surgical Procedures Gynecology 12(26.7) 14(31.8) 11(25) 0.758 General Surgery 30(66.7) 28(63.6) 26(59.1) 0.758 Urology 3(6.7) 2(4.5) 7(15.9) 0.154 M：Mask Group；T：High-Flow Nasal Cannula Group；M+T：Combined THRIV and Mask Group; OSAS, obstructive sleep apnea syndrome ；BP: blood pressure; SBP: Systolic Blood Pressure; DBP: Diastolic Blood Pressure 1. The incidence of increased intragastric pressure As shown in Table 2, in the comparison of the difference between P3 and P1, the increase of intragastric pressure in Group T and Group M+T was significantly lower than in Group M ( P < 0.05). The positive rate (also means the incidence of increased intragastric pressure) in Group T and Group M+T was also significantly lower than in Group M ( P < 0.05). There were significant differences in P2 among the three groups ( P < 0.05). The highest intragastric pressure in Group T and Group M+T was significantly lower than that in Group M. Within Group M, intragastric pressure at P2 was considerably higher than at P1 and P3 ( P < 0.05). 2. The direct grading of gastric insufflation, Antral cross-section area In three groups, there were no significant differences in the grading of gastric insufflation under direct laparoscopic visualization (Table 2). However, the number of patients with CSAa was lower in Group T and Group M+T compared with Group M, with statistically significant differences ( P < 0.05) (Table 2). Table 2- Comparison of Intragastric Pressure Changes Group M (n=45) Group T (n=44) Group M+T (n=44) P value P1 (cmH 2 O); x̄ ±s 11.2±2.1 # 11.4±1.9 11.3±1.6 0.845 P2 (cmH 2 O); x̄ ±s 14.5±2.5 11.7±2.0 * 11.8±2.1 * 0.001 P3 (cmH 2 O); x̄ ±s 11.8±2.7 # 11.6±1.9 11.6±1.9 0.768 P3-P1 (cmH 2 O); x̄ ±s 0.7±0.9 0.1±0.4 * 0.1±0.4 * 0.001 positive/negative (n) 17/28 5/39 * 6/38 * 0.003 Laparoscopic grading of gastric Insufflation (n) (I/II) 35/10 41/3 40/4 0.063 Laparoscopic grading of gastric Insufflation (n) (III/IV) 0/0 0/0 0/0 - Significant changes in CSAa (yes/no) 27/18 9/35 * 8/36 * 0.000 P1: Initial intragastric pressure; P2: Peak intragastric pressure; P3: Final intragastric pressure; P3 - P1: Intragastric pressure difference; CSAa: Cross-sectional area of the gastric antrum; Significant changes in CSAa: Fluctuations in the cross-sectional area of the gastric antrum exceeding 10% as assessed by ultrasound. *: Compared with Group M, P < 0.05. #: Compared with P2, P < 0.05. 3. Oxygenation Status According to the statistical results in Table 3, in T3 and T5, the lowest oxygen saturation was significantly higher in Group T and Group M+T compared with Group M ( P < 0.05). The PEtO₂ of T4 and T5 was also significantly higher in Group T and Group M+T compared with Group M ( P < 0.05). Table 3- Comparison of Oxygenation Status Among the Three Groups Group M (n=45) Group T (n=44) Group M+T (n=44) P value SpO 2 (%); M (IQR) T1 98 (97, 99) 98 (97, 99) 98 (98, 99) 0.238 T2 100 (100, 100) 100 (100, 100) 100 (100, 100) - T3 100 (99, 100) 100 (100, 100) * 100 (100, 100) * 0.012 T5 100 (99, 100) 100 (100, 100) * 100 (100, 100) * 0.024 PEtO 2 (%); x̄ ±s T2 91.0±0.8 91.0±1.0 91.2±1.0 0.705 T4 82.8±2.5 86.5±2.0 * 87.2±2.3 * 0.001 T5 79.7±2.5 84.0±2.3 * 83.9±2.8 * 0.001 PEtCO 2 (mmHg); x̄ ±s T2 35.0±0.8 35.1±1.0 35.2±1.1 0.605 T4 39.0±1.5 40.1±1.7 * 40.0±1.6 * 0.002 T5 39.9±1.6 40.9±1.7 * 40.8±1.7 * 0.012 T1: before oxygenation; T2: after preoxygenation; T3: lowest value before mechanical ventilation; T4: first complete breath waveform after mechanical ventilation; T5: lowest value within 2 minutes of mechanical ventilation. *: Compared with Group M, P < 0.05. 4.Adverse events Postoperative nausea and vomiting occurred in all three groups, but there were no statistically significant differences in the incidence of postoperative nausea and vomiting among the groups. See Table 4. Table4.Comparison of General Adverse Events Among Three Groups of Cases (n(%)) Group M (n=45) Group T (n=44) Group M+T (n=44) P value PONV 8 (17.8) 7 (15.9) 8 (18.2) 0.956 Pharyngalgia 0 0 0 - Pneumothorax, Subcutaneous Emphysema 0 0 0 - Epistaxis 0 0 0 - PONV: Postoperative Nausea and Vomiting; M：Mask Group；T：High-Flow Nasal Cannula Group；M+T：Combined THRIV and Mask Group. Discussion The findings of this study suggest that, the use of THRIVE for anaesthesia induction in overweight patients was associated with lower the incidence of elevated intragastric pressure while ensuring adequate oxygenation, when compared with facemask alone. Among young adults in developing countries, the prevalence of obesity ranges from 2.3–12%, with an overweight prevalence of 28.8% . [ 17 ] Obese patients are at a significantly higher risk of perioperative pulmonary complications and gastric insufflation compared with other persons of normal build. [ 18 ] Our study demonstrates that, compared with mask ventilation, THRIVE significantly lowers the incidence of increased intragastric pressure. Previous studies have often reported that facemask ventilation is associated with gastric insufflation. [ 3 , 19 , 20 ] These studies typically evidenced by indirect indicators such as ultrasonography of the gastric antrum area or auscultation of air sounds. In contrast, our direct measurement of intragastric pressure provides a more reliable indication of the occurrence of gastric insufflation. Groves et al. measured this airway pressure in volunteers and found that, at a flow rate of 60 l min − 1 , the positive pressure was approximately 7.4 cmH₂O. [ 21 ] This lower positive pressure, as generated by THRIVE, is sufficient to maintain alveolar patency and improve oxygenation without significantly affecting intragastric pressure. Our results showed that the M group had more patients with gastric antral area changes exceeding 10% compared with the T and M + T groups. Previous studies have identified a correlation between elevated gastric antral cross-sectional area (CSAa) and gastric insufflation, suggesting that air entering the stomach significantly increases CSA by acting on the gastric wall. [ 3 , 22 ] Gastric ultrasound is a relatively accurate method for the volume and nature of gastric contents. However, some studies have shown that it can be challenging to perform in obese patients, even for experienced operators. [ 23 ] The gastric antral area in obese patients is larger than that in normal individuals, [ 24 ] which may be related to the increased gastric volume or thickened gastric wall in obese patients. Considering that our study involved overweight patients and that ultrasonography and laparoscopic grading may have some bias or subjectivity, we primarily used a pressure sensor to detect changes in intragastric pressure. Ultrasonography and direct visualization were used as supplementary methods to support our findings. However, our laparoscopic grading of gastric insufflation, which was subjectively judged by surgeons, revealed no significant differences among the three groups, despite a higher incidence of gastric insufflation in the M group. This discrepancy may be attributed to varying definitions of acceptable gastric insufflation among different surgical specialties, as well as potential biases inherent in subjective assessments. Our study revealed that, compared with the M group, the T group and the M + T group achieved higher minimum SpO₂ levels and significantly prolonged the duration of safe oxygenation. Wong et al. [ 16 ] similarly found that THRIVE provides a longer duration of safe apnea compared with conventional oxygenation during induction of anaesthesia in obese patients, with an approximate increase of 76 seconds (40%). Additionally, the T group and the M + T group exhibited higher PEtO₂ levels, findings that are consistent with the study by Samir et al. [ 25 ] These observations can be attributed to several key factors. First, THRIVE's ability to provide positive end-expiratory pressure (PEEP) . [ 26 ] During apnea, continuous infusion of 37°C, 100% humidified pure oxygen allows oxygen to passively enter the alveoli by utilizing the negative pressure gradient within the alveoli and cardiogenic oscillations, thereby maintaining oxygenation. Notably, the PEEP effect of THRIVE is influenced by various factors, such as anatomical differences in the nasopharyngeal cavity, gas flow rate, and patient positioning. To optimize these conditions, we employed chin lift or jaw thrust to ensure a closed mouth and patency of the upper airway. By delivering a gas flow exceeding the patient’s inspiratory flow rate, THRIVE can flush out residual CO₂ from the dead space, reducing CO₂ reabsorption and enhancing effective ventilation. Jeong et al. [ 27 ] found in their emergency department study that the use of high-flow nasal cannula in patients with hypercapnia showed a significant trend in reducing PaCO2. However, in our study, the T group and M + T group exhibited higher end-tidal CO₂ levels than the M group. This may be due to two main reasons: Firstly, it was only applied for two minutes after apnea. Secondly, THRIVE primarily flushes carbon dioxide from the dead space, but it has minimal impact on carbon dioxide in alveolar ventilation. Under apneic conditions, THRIVE may be less effective than mask ventilation in removing carbon dioxide from the alveoli. This is also why guidelines do not recommend THRIVE for patients with hypercapnia. Nevertheless, the differences in our study were small and are likely to be clinically insignificant. The M + T group was established in our study to assess whether it could offer superior oxygenation and reduced gastric insufflation compared with the T group. However, no significant differences were observed between these two groups in terms of these outcomes. This discrepancy from the prior findings [ 25 ] may be due to the fact that, in our setup, the masks in M + T group were not required to be tightly sealed. Regarding postoperative adverse events, no airway-related complications were noted in the THRIVE groups. There were no significant differences among the three groups in terms of overall adverse events. Nausea and vomiting occurred across all groups, likely attributable to anaesthetic agents and surgical stimulation, with no significant differences observed. Given the relatively short duration of THRIVE use in this study, potential airway injury from prolonged application was not evaluated. This study provides direct pressure data to validate stomach-related changes during mask ventilation induction, further supporting the link between mask ventilation and gastric insufflation, regurgitation, and aspiration. While THRIVE outperforms mask ventilation in reducing gastric insufflation, its limited CO₂ clearance capability should not be overlooked. Future research could explore a balanced preoxygenation method that addresses both issues. Previous studies have mostly focused on healthy patients. The data of intragastric pressure in obese patients provide valuable insights, laying a foundation for further research and adding evidence to support the application of THRIVE. Limitations The sample size of this study was relatively small, particularly among obese patients. The presence of outliers may have introduced significant variability into the dataset, potentially affecting the robustness of the study results. Additionally, we did not further categorize the degree of overweight, with patients' BMIs ranging from just above 25 kg m − 2 to over 35 kg m − 2 . Therefore, the effects of THRIVE on individuals with different degrees of overweight remain to be elucidated. Conclusion This randomized controlled trial demonstrates that THRIVE minimizes changes in intragastric pressure and provides superior oxygenation during anaesthesia induction in overweight patients. The THRIVE technique emerges as a practical and effective option compared with the current standard of mask ventilation. Abbreviations THRIVE ： Transnasal Humidified Rapid Insufflation Ventilatory Exchange BMI ： Body Mass Index PEtO 2 ： partial pressure of end-tidal oxygen SpO 2 ： Saturation of Peripheral Oxygen PEtCO2 ： partial pressure of end-tidal carbon dioxide GERD ： gastroesophageal reflux disease LES ： lower esophageal sphincter FRC ： functional residual capacity ERV ： expiratory reserve volume HFNC ： high-flow nasal cannula ECG ： Electrocardiogram NIBP ： non-invasive blood pressure PCV ： Pressure Controlled Ventilation TV ： Tidal volume PEEP: Positive End-expiratory Pressure CSAa: Cross-sectional area of the gastric antrum Declarations Ethics approval and consent to participate This prospective randomized controlled trial was approved by the Ethics Committee of the 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China (Approval No. KY2023-195; Chairperson: Professor Zimiao Chen) on 4 September 2023. The trial was prospectively registered at the China Clinical Trial Registration Center (Registration No. ChiCTR2300075652) prior to patient enrolment. Written informed consent was obtained from all participants or their legally authorized representatives before enrollment. Participants (or their proxies) were thoroughly informed of the study’s objectives, interventions, potential risks, benefits, and the right to withdraw at any time without affecting their clinical care. All methods were carried out in accordance with relevant guidelines and regulations (Declaration of Helsinki) Consent for publication Not applicable Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests Funding This study received no external funding from any organization or institution. Authors' contributions CY: Study conceptualization and design, drafting the initial manuscript, and critical revision of the final manuscript. YH: Experimental design and execution, data acquisition, and preliminary analysis. TY: Literature review, data interpretation, and methodological optimization for data analysis. SH: Statistical modeling, advanced data analysis, and validation. ZY: Critical revision of literature and development of the logical framework for result interpretation. JQ: Key revisions to the methodology and discussion sections, academic compliance review. MY: Overall study design oversight, quality control of experiments, and final manuscript approval. LH: Cross-disciplinary resource coordination, ethics and funding compliance, and final manuscript approval. Acknowledgements Not applicable Authors' information (optional) References Cajander P, Edmark L, Ahlstrand R, Magnuson A, de Leon A. 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Evaluation of adequacy of ventilation and gastric insufflation at three levels of inspiratory pressure for facemask ventilation during induction of anaesthesia: A randomised controlled trial. Anaesth Crit Care Pain Med. 2022. 41(5): 101132. Isono S, Eikermann M, Odaka T. Facemask ventilation during induction of anesthesia: how "gentle" is "gentle" enough. Anesthesiology. 2014. 120(2): 263-5. Groves N, Tobin A. High flow nasal oxygen generates positive airway pressure in adult volunteers. Aust Crit Care. 2007. 20(4): 126-31. Qian X, Hu Q, Zhao H, et al. Determination of the optimal inspiratory pressure providing adequate ventilation while minimizing gastric insufflation using real-time ultrasonography in Chinese children: a prospective, randomized, double-blind study. BMC Anesthesiol. 2017. 17(1): 126. Van de Putte P, Perlas A. Gastric sonography in the severely obese surgical patient: a feasibility study. Anesth Analg. 2014. 119(5): 1105-10. Bouvet L, Mazoit JX, Chassard D, Allaouchiche B, Boselli E, Benhamou D. Clinical assessment of the ultrasonographic measurement of antral area for estimating preoperative gastric content and volume. Anesthesiology. 2011. 114(5): 1086-92. Jaber S, De Jong A, Schaefer MS, et al. Preoxygenation with standard facemask combining apnoeic oxygenation using high flow nasal cannula versuss standard facemask alone in patients with and without obesity: the OPTIMASK international study. Ann Intensive Care. 2023. 13(1): 26. Coussa M, Proietti S, Schnyder P, et al. Prevention of atelectasis formation during the induction of general anesthesia in morbidly obese patients. Anesth Analg. 2004. 98(5): 1491-5, table of contents. Jeong JH, Kim DH, Kim SC, et al. Changes in arterial blood gases after use of high-flow nasal cannula therapy in the ED. Am J Emerg Med. 2015. 33(10): 1344-9. Additional Declarations No competing interests reported. Supplementary Files THRIVEprotocol.docx CONSORT2010Checklist.doc Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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Affiliated Hospital of Wenzhou Medical University","correspondingAuthor":true,"prefix":"","firstName":"Mo","middleName":"","lastName":"Yunchang","suffix":""},{"id":498155658,"identity":"21e32d34-2bce-40bb-8aec-f3db1fd55b99","order_by":7,"name":"Li Hang","email":"","orcid":"","institution":"Affiliated Dongyang Hospital of Wenzhou Medical University","correspondingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"Hang","suffix":""}],"badges":[],"createdAt":"2025-06-08 14:38:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6848070/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6848070/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88780527,"identity":"78d4e2e7-1b91-475b-a5fd-c1ba1c1bb857","added_by":"auto","created_at":"2025-08-11 10:47:27","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":187568,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStudy protocol\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6848070/v1/666f08c93330880b585f4a98.png"},{"id":88781894,"identity":"4e237dc6-17ef-4b77-a6d2-3d3d3b95b11d","added_by":"auto","created_at":"2025-08-11 10:55:27","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":184247,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFlow chart\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6848070/v1/8925af8df1675f000abb8a01.png"},{"id":95722081,"identity":"7c2574f4-3247-4d21-810a-9f3838c586cf","added_by":"auto","created_at":"2025-11-12 09:39:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1312147,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6848070/v1/60b60b62-3cc5-4229-a2b8-d185ebc7d3f6.pdf"},{"id":88781892,"identity":"152a64e5-0d6f-46f3-a505-8fa15666f063","added_by":"auto","created_at":"2025-08-11 10:55:27","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":88656,"visible":true,"origin":"","legend":"","description":"","filename":"THRIVEprotocol.docx","url":"https://assets-eu.researchsquare.com/files/rs-6848070/v1/100c4eb8cb39d9c877b012bd.docx"},{"id":88780541,"identity":"6b5bd6b0-5ded-4e87-bf01-1604e50a7edd","added_by":"auto","created_at":"2025-08-11 10:47:27","extension":"doc","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":223232,"visible":true,"origin":"","legend":"","description":"","filename":"CONSORT2010Checklist.doc","url":"https://assets-eu.researchsquare.com/files/rs-6848070/v1/67e71e464e74130f38ba1603.doc"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Impact of Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE) on Intragastric Pressure During Anaesthesia Induction in Overweight Patients: A Randomized Controlled Trial","fulltext":[{"header":"Introduction","content":"\u003cp\u003eDuring anaesthesia induction, positive pressure ventilation masks are frequently utilized to prevent hypoxia. However, this method may cause gastric insufflation, thereby increasing the risks of reflux, aspiration, and postoperative nausea and vomiting.\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e Notably, aspiration is a significant cause of anaesthesia-related mortality.\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e While pressure-controlled mask ventilation with a pressure setting below 15 cmH₂O\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e can mitigate the risk of gastric insufflation, anaesthesiologists must maintain alertness, especially in high-risk populations such as overweight patients.\u003c/p\u003e\u003cp\u003eHashem et al\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e identified obesity as a strong independent risk factor for gastroesophageal reflux disease (GERD), with the probability being 2.5 times higher than that in the general population. Studies have shown that compared with normal individuals, obese patients are more prone to experiencing a decrease in lower esophageal sphincter (LES) pressure both after meals and during anaesthesia.\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e Therefore, we reasonably speculate that overweight patients are a key population at risk of gastric insufflation and reflux during anaesthesia induction.\u003c/p\u003e\u003cp\u003eMoreover, a study in North America showed that when a patient's BMI is 30 kg m\u003csup\u003e− 2\u003c/sup\u003e, their functional residual capacity (FRC) and expiratory reserve volume (ERV) are only 75% and 47%, respectively, of those of patients with a BMI of 20 kg m\u003csup\u003e− 2\u003c/sup\u003e.\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e Other finding highlights that obesity impairs respiratory muscle function, increases oxygen consumption, reduces pulmonary compliance, and affects gas exchange, ultimately resulting in poor oxygenation.\u003csup\u003e[\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e–\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e Collectively, these findings suggest that overweight patients possess limited oxygen reserves and are predisposed to hypoxemia during the induction, as well as a higher risk of gastric insufflation and aspiration. It suggests that further optimisation of the method of oxygenation is required to minimise gastric insufflation during the induction of anaesthesia in overweight patients.\u003c/p\u003e\u003cp\u003eTrans-nasal humidified rapid insufflation ventilatory exchange (THRIVE), also known as high-flow nasal cannula (HFNC) oxygen therapy, is a noninvasive oxygen therapy that directly delivers a specific concentration of high-flow air-oxygen mixed gas to the patient through heating and humidification. THRIVE enhances ventilation and oxygenation while reducing anatomical dead space in the upper airway and decreasing the work of breathing. This modality has been applied in pre-intubation preoxygenation, treatment of respiratory failure, respiratory support after major surgery, and oxygen therapy following extubation.\u003csup\u003e[\u003cspan additionalcitationids=\"CR12 CR13 CR14\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e–\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e Research has shown that compared with conventional oxygenation, THRIVE provides a longer safe apnea time and higher minimum oxygen saturation in morbidly obese patients during anaesthesia induction.\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e We hypothesize that THRIVE can reduce changes in intragastric pressure while effectively ensuring oxygenation during the induction of general anaesthesia in overweight patients.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cb\u003eStudy Design and Participants\u003c/b\u003e\u003c/p\u003e\u003cp\u003e The study received approval from the Ethics Committee of the 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China, on 4 September 2023(KY2023-195), Chairperson Professor Zimiao Chen. And it was registered in the China Clinical Trial Registration Center (ChiCTR2300075652) before patient enrolment. All participants provided written informed consent upon enrollment in the study. This manuscript adheres to the Consolidated Standards of Reporting Trials (CONSORT) guidelines.\u003c/p\u003e\u003cp\u003eAdult patients (18–65 years), ASA class I-II, BMI ≥ 25, requiring anaesthesia induction without special position requirements, were enrolled after written consent during pre-operative evaluation. Exclusion criteria were as follows: difficult airway; skull base fractures; active bleeding in the airway or upper digestive tract, or with esophageal varices; pregnancy; severe gastroesophageal reflux disease; neuromuscular disorders; ASA ≥ III.\u003c/p\u003e\u003cp\u003e\u003cb\u003eRandomization and Blinding\u003c/b\u003e\u003c/p\u003e\u003cp\u003eEligible patients were blindly and randomly assigned to three groups according to computer-generated random codes. These codes were kept in sealed opaque envelopes. A large sterile surgical towel was hung around the patient's neck to separate the surgeon and the anaesthesiologist using ultrasound on the other side, ensuring they were also unaware of the group assignments. The monitor screen was turned to the opposite side, and the data recorder faced away from the procedure to document the data, remaining unaware of the group assignments. Both the anaesthesiologist and the surgeon were blinded to the group allocation.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStudy protocol\u003c/b\u003e\u003c/p\u003e\u003cp\u003ePatients who met the inclusion criteria were randomly assigned to three groups. The mask group (M group) received pressure-controlled ventilation via a face mask. The transnasal Humidified Rapid Insufflation Ventilatory Exchange group (T group) received oxygen via high-flow nasal cannula. The combined mask and THRIVE group (M + T group) received oxygen via high-flow nasal cannula with a face mask loosely applied over the mouth and nose.\u003c/p\u003e\u003cp\u003eAll patients were first preoxygenated with a tight-fitting facemask, which delivered 100% oxygen and a fresh gas flow of 8 L min\u003csup\u003e− 1\u003c/sup\u003e to reach PEtO\u003csub\u003e2\u003c/sub\u003e \u0026gt; 90%, and ECG, NIBP, heart rate, and pulse oximetry monitoring were applied. Using propofol (1.5–2.5 mg kg\u003csup\u003e− 1\u003c/sup\u003e), sufentanil (0.2–0.4 µg kg\u003csup\u003e− 1\u003c/sup\u003e), and rocuronium bromide (0.3–0.6 mg kg\u003csup\u003e− 1\u003c/sup\u003e) for anaesthetic agents. If significant hemodynamic fluctuations occur during induction, appropriate vasopressors should be administered. After loss of consciousness (disappearance of eyelash reflex), a gastric pressure measurement tube was inserted orally into the stomach under the guidance of a video laryngoscope in all groups (insertion was confirmed by the aspiration of gastric fluid). The tube was then connected to a disposable pressure transducer that had been pre-set to measure central venous pressure and calibrated to the mid-axillary line.\u003c/p\u003e\u003cp\u003eSubsequently, in the M group, patients were ventilated by the PCV mode in anaesthesia machine (Pinsp = 15 cmH\u003csub\u003e2\u003c/sub\u003eO, TV = 8 L min\u003csup\u003e− 1\u003c/sup\u003e, RR = 12 breaths per min with 100% oxygen) via face mask. The T group received high-flow nasal cannula ventilation at a rate of 60 L min\u003csup\u003e− 1\u003c/sup\u003e with 100% oxygen. Airway patency was maintained using a chin lift or jaw thrust. The M + T group used a ventilation mode like T group, while adding a loosely fitting face mask at the rate of 8 L min\u003csup\u003e− 1\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eAfter 2 minutes of apnoeic oxygenation, intubation or laryngeal mask airway was performed, and mechanical ventilation was initiated (TV = 6–8 l min\u003csup\u003e− 1\u003c/sup\u003e, RR = 15, 100% oxygen flow rate of 1 l min\u003csup\u003e− 1\u003c/sup\u003e, PEEP = 5) for 2 minutes. Then record monitoring data. (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDuring the trial, the anaesthesiologist performed ultrasonographic measurements of the gastric antral area before and after ventilation. The calculation formula: CSAa (cm²) = π × anteroposterior diameter of the gastric antrum (cm) × craniocaudal diameter of the gastric antrum (cm) ÷ 4. Additionally, the surgeon graded gastric insufflation under direct laparoscopic visualization: Grade I, No Distension; Grade II, Mild Distension; Grade III, Moderate Distension that affects the surgical view but does not interfere with operation; Grade IV, Severe Distension that necessary measures should be taken, such as nasogastric tube or percutanaeous aspiration.\u003c/p\u003e\u003cp\u003eThe primary outcome was the incidence of increased intragastric pressure. The initial pressure measured upon insertion of the intragastric pressure catheter was recorded as P1. The highest-pressure during ventilation was recorded as P2. The pressure at the end of ventilation was recorded as P3. Cases with P3-P1 \u0026gt; 0 were defined as positive cases.\u003c/p\u003e\u003cp\u003eThe secondary outcomes included the grading of gastric insufflation, CSAa, SpO₂, PEtO₂, and PEtCO₂ levels at different time points (T1: before oxygenation; T2: after preoxygenation; T3: lowest value before mechanical ventilation; T4: first complete breath waveform after mechanical ventilation; T5: lowest value within 2 minutes of mechanical ventilation), and the incidence of adverse events.\u003c/p\u003e\u003cp\u003e\u003cb\u003eSample size evaluation\u003c/b\u003e\u003c/p\u003e\u003cp\u003eBased on the pilot study results, the mean differences in intragastric pressure for groups M, T, and M + T were 0.6 mmHg, 0.2 mmHg, and 0.2 mmHg, respectively, with standard deviations of 0.49 mmHg, 0.4 mmHg, and 0.4 mmHg. Using GPower 3.1 software, with a Type I error rate (α) of 0.05 and power (1 - β) of 0.90, the calculated sample size was 30 patients per group. Considering the difficulties in gastric intubation and potential data loss, we decided to include 135 patients.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStatistical Methods\u003c/b\u003e\u003c/p\u003e\u003cp\u003eStatistical analyses were performed using SPSS 25 software. Normally distributed continuous data were presented as mean ± standard deviation (SD). Repeated measures analysis of variance (ANOVA) was used for within-group comparisons, while one-way ANOVA was used for between-group comparisons. Post hoc comparisons were conducted using the LSD method. For non-normally distributed continuous data, the median (M) and interquartile range (IQR) were used, and within-group comparisons were performed using the Wilcoxon signed-rank test. Categorical data were expressed as frequency counts or percentages (%), and comparisons were made using the chi-square test. A \u003cem\u003eP\u003c/em\u003e-value less than 0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003eBased on the inclusion and exclusion criteria, one hundred and thirty-five patients were enrolled between September, 2023, and January, 2024 at the 1\u003csup\u003est\u003c/sup\u003e Affiliated Hospital of Wenzhou Medical University. Two patients were excluded (Fig. 2). There were no significant differences between the three groups in terms of baseline characteristics (Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1-Baseline patient characteristics of three groups\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" class=\"fr-table-selection-hover\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup M (n=45)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup T (n=44)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup M+T (n=44)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eP\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAge (y); \u0026nbsp; x̄ \u0026plusmn;s\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e44.6\u0026plusmn;10.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e44.5\u0026plusmn;10.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e44.1\u0026plusmn;11.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.979\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSex (male/ female)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e18/27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e15/29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e16/28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.844\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBMI (kg.m\u003csup\u003e2\u003c/sup\u003e); \u0026nbsp; x̄ \u0026plusmn;s\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e29.0\u0026plusmn;3.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e29.1\u0026plusmn;2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e28.8\u0026plusmn;3.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.915\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eASA (I/II)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6/39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6/38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5/39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.942\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMallampatti class (I/II)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e25/20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e30/14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e31/13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.284\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eOSAS（0/1/2）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e14/28/3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e14/25/5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e19/19/6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.434\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBP（mmHg）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSBP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e146.6\u0026plusmn;18.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e147.4\u0026plusmn;18.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e141.2\u0026plusmn;20.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.265\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eDBP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e82.9\u0026plusmn;13.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e84.5\u0026plusmn;10.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e80.6\u0026plusmn;12.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.377\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHeart Rate（bpm）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e75.9\u0026plusmn;15.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e74.3\u0026plusmn;12.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e72.2\u0026plusmn;10.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.412\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSurgical Procedures\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGynecology\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e12(26.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e14(31.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11(25)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.758\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGeneral Surgery\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e30(66.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e28(63.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e26(59.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.758\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eUrology\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3(6.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2(4.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e7(15.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.154\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eM：Mask Group；T：High-Flow Nasal Cannula Group；M+T：Combined THRIV and Mask Group;\u0026nbsp;OSAS, obstructive sleep apnea syndrome\u0026nbsp;；BP: blood pressure; SBP:\u0026nbsp;Systolic Blood Pressure; DBP:\u0026nbsp;Diastolic Blood Pressure\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1. The incidence of increased intragastric pressure\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs shown in Table 2, in the comparison of the difference between P3 and P1, the increase of intragastric pressure in Group T and Group M+T was significantly lower than in Group M (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). The positive rate (also means the incidence of increased intragastric pressure) in Group T and Group M+T was also significantly lower than in Group M (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). There were significant differences in P2 among the three groups (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). The highest intragastric pressure in Group T and Group M+T was significantly lower than that in Group M. Within Group M, intragastric pressure at P2 was considerably higher than at P1 and P3 (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eThe direct grading of gastric insufflation, Antral cross-section area\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn three groups, there were no significant differences in the grading of gastric insufflation under direct laparoscopic visualization (Table 2).\u0026nbsp;However, the number of patients with CSAa was lower in Group T and Group M+T compared with Group M, with statistically significant differences (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05) (Table 2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2- Comparison of Intragastric Pressure Changes\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup M\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=45)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup T (n=44)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup M+T (n=44)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eP value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eP1 (cmH\u003csub\u003e2\u003c/sub\u003eO); \u0026nbsp;x̄ \u0026plusmn;s\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.2\u0026plusmn;2.1\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.4\u0026plusmn;1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.3\u0026plusmn;1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.845\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eP2 (cmH\u003csub\u003e2\u003c/sub\u003eO); \u0026nbsp;x̄ \u0026plusmn;s\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e14.5\u0026plusmn;2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.7\u0026plusmn;2.0\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.8\u0026plusmn;2.1\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eP3 (cmH\u003csub\u003e2\u003c/sub\u003eO); \u0026nbsp;x̄ \u0026plusmn;s\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.8\u0026plusmn;2.7\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.6\u0026plusmn;1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.6\u0026plusmn;1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.768\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eP3-P1 (cmH\u003csub\u003e2\u003c/sub\u003eO); \u0026nbsp; x̄ \u0026plusmn;s\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.7\u0026plusmn;0.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.1\u0026plusmn;0.4\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.1\u0026plusmn;0.4\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003epositive/negative\u0026nbsp;(n)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e17/28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5/39\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6/38\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eLaparoscopic grading of gastric Insufflation (n) (I/II)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e35/10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e41/3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e40/4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.063\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eLaparoscopic grading of gastric Insufflation (n) (III/IV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0/0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0/0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0/0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSignificant changes in CSAa (yes/no)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e27/18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e9/35\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e8/36\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eP1: Initial intragastric pressure; P2: Peak intragastric pressure; P3: Final intragastric pressure; P3 - P1: Intragastric pressure difference; CSAa: Cross-sectional area of the gastric antrum; Significant changes in CSAa: Fluctuations in the cross-sectional area of the gastric antrum exceeding 10% as assessed by ultrasound.\u003c/p\u003e\n\u003cp\u003e*:\u0026nbsp;Compared with Group M, P \u0026lt; 0.05.\u003c/p\u003e\n\u003cp\u003e#: Compared with P2, P \u0026lt; 0.05.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eOxygenation Status\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAccording to the statistical results in Table 3, in T3 and T5, the lowest oxygen saturation was significantly higher in Group T and Group M+T compared with Group M (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). The PEtO₂ of T4 and T5 was also significantly higher in Group T and Group M+T compared with Group M (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3-\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eComparison of Oxygenation Status Among the Three Groups\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup M (n=45)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup T\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=44)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup M+T (n=44)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eP\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSpO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(%); M (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e98 (97, 99)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e98 (97, 99)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e98 (98, 99)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.238\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (100, 100)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (100, 100)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (100, 100)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (99, 100)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (100, 100)\u003csup\u003e\u0026nbsp;*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (100, 100)\u003csup\u003e\u0026nbsp;*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.012\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (99, 100)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (100, 100)\u003csup\u003e\u0026nbsp;*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100 (100, 100)\u003csup\u003e\u0026nbsp;*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.024\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePEtO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(%); \u0026nbsp;x̄ \u0026plusmn;s\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e91.0\u0026plusmn;0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e91.0\u0026plusmn;1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e91.2\u0026plusmn;1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.705\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e82.8\u0026plusmn;2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e86.5\u0026plusmn;2.0\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e87.2\u0026plusmn;2.3\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e79.7\u0026plusmn;2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e84.0\u0026plusmn;2.3\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e83.9\u0026plusmn;2.8\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePEtCO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(mmHg); \u0026nbsp; x̄ \u0026plusmn;s\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e35.0\u0026plusmn;0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e35.1\u0026plusmn;1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e35.2\u0026plusmn;1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.605\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e39.0\u0026plusmn;1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e40.1\u0026plusmn;1.7\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e40.0\u0026plusmn;1.6\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e39.9\u0026plusmn;1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e40.9\u0026plusmn;1.7\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e40.8\u0026plusmn;1.7\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.012\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eT1: before oxygenation; T2: after preoxygenation; T3: lowest value before mechanical ventilation; T4: first complete breath waveform after mechanical ventilation; T5: lowest value within 2 minutes of mechanical ventilation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e*: Compared with Group M, P \u0026lt; 0.05.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.Adverse events\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePostoperative nausea and vomiting occurred in all three groups, but there were no statistically significant differences in the incidence of postoperative nausea and vomiting among the groups. See Table 4.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable4.Comparison of General Adverse Events Among Three Groups of Cases\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(n(%))\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup M (n=45)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup T (n=44)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup M+T (n=44)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eP\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePONV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e8 (17.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e7 (15.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e8 (18.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.956\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePharyngalgia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePneumothorax,\u0026nbsp;Subcutaneous Emphysema\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eEpistaxis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003ePONV: Postoperative Nausea and Vomiting; M：Mask Group；T：High-Flow Nasal Cannula Group；M+T：Combined THRIV and Mask Group.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe findings of this study suggest that, the use of THRIVE for anaesthesia induction in overweight patients was associated with lower the incidence of elevated intragastric pressure while ensuring adequate oxygenation, when compared with facemask alone.\u003c/p\u003e\u003cp\u003eAmong young adults in developing countries, the prevalence of obesity ranges from 2.3\u0026ndash;12%, with an overweight prevalence of 28.8% .\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e Obese patients are at a significantly higher risk of perioperative pulmonary complications and gastric insufflation compared with other persons of normal build.\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eOur study demonstrates that, compared with mask ventilation, THRIVE significantly lowers the incidence of increased intragastric pressure. Previous studies have often reported that facemask ventilation is associated with gastric insufflation.\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e These studies typically evidenced by indirect indicators such as ultrasonography of the gastric antrum area or auscultation of air sounds. In contrast, our direct measurement of intragastric pressure provides a more reliable indication of the occurrence of gastric insufflation. Groves et al. measured this airway pressure in volunteers and found that, at a flow rate of 60 l min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the positive pressure was approximately 7.4 cmH₂O.\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e This lower positive pressure, as generated by THRIVE, is sufficient to maintain alveolar patency and improve oxygenation without significantly affecting intragastric pressure.\u003c/p\u003e\u003cp\u003eOur results showed that the M group had more patients with gastric antral area changes exceeding 10% compared with the T and M\u0026thinsp;+\u0026thinsp;T groups. Previous studies have identified a correlation between elevated gastric antral cross-sectional area (CSAa) and gastric insufflation, suggesting that air entering the stomach significantly increases CSA by acting on the gastric wall.\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e Gastric ultrasound is a relatively accurate method for the volume and nature of gastric contents. However, some studies have shown that it can be challenging to perform in obese patients, even for experienced operators.\u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e The gastric antral area in obese patients is larger than that in normal individuals,\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e which may be related to the increased gastric volume or thickened gastric wall in obese patients. Considering that our study involved overweight patients and that ultrasonography and laparoscopic grading may have some bias or subjectivity, we primarily used a pressure sensor to detect changes in intragastric pressure. Ultrasonography and direct visualization were used as supplementary methods to support our findings.\u003c/p\u003e\u003cp\u003eHowever, our laparoscopic grading of gastric insufflation, which was subjectively judged by surgeons, revealed no significant differences among the three groups, despite a higher incidence of gastric insufflation in the M group. This discrepancy may be attributed to varying definitions of acceptable gastric insufflation among different surgical specialties, as well as potential biases inherent in subjective assessments.\u003c/p\u003e\u003cp\u003eOur study revealed that, compared with the M group, the T group and the M\u0026thinsp;+\u0026thinsp;T group achieved higher minimum SpO₂ levels and significantly prolonged the duration of safe oxygenation. Wong et al. \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e similarly found that THRIVE provides a longer duration of safe apnea compared with conventional oxygenation during induction of anaesthesia in obese patients, with an approximate increase of 76 seconds (40%). Additionally, the T group and the M\u0026thinsp;+\u0026thinsp;T group exhibited higher PEtO₂ levels, findings that are consistent with the study by Samir et al.\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e These observations can be attributed to several key factors. First, THRIVE's ability to provide positive end-expiratory pressure (PEEP) .\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e During apnea, continuous infusion of 37\u0026deg;C, 100% humidified pure oxygen allows oxygen to passively enter the alveoli by utilizing the negative pressure gradient within the alveoli and cardiogenic oscillations, thereby maintaining oxygenation. Notably, the PEEP effect of THRIVE is influenced by various factors, such as anatomical differences in the nasopharyngeal cavity, gas flow rate, and patient positioning. To optimize these conditions, we employed chin lift or jaw thrust to ensure a closed mouth and patency of the upper airway.\u003c/p\u003e\u003cp\u003eBy delivering a gas flow exceeding the patient\u0026rsquo;s inspiratory flow rate, THRIVE can flush out residual CO₂ from the dead space, reducing CO₂ reabsorption and enhancing effective ventilation. Jeong et al.\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e found in their emergency department study that the use of high-flow nasal cannula in patients with hypercapnia showed a significant trend in reducing PaCO2. However, in our study, the T group and M\u0026thinsp;+\u0026thinsp;T group exhibited higher end-tidal CO₂ levels than the M group. This may be due to two main reasons: Firstly, it was only applied for two minutes after apnea. Secondly, THRIVE primarily flushes carbon dioxide from the dead space, but it has minimal impact on carbon dioxide in alveolar ventilation. Under apneic conditions, THRIVE may be less effective than mask ventilation in removing carbon dioxide from the alveoli. This is also why guidelines do not recommend THRIVE for patients with hypercapnia. Nevertheless, the differences in our study were small and are likely to be clinically insignificant.\u003c/p\u003e\u003cp\u003eThe M\u0026thinsp;+\u0026thinsp;T group was established in our study to assess whether it could offer superior oxygenation and reduced gastric insufflation compared with the T group. However, no significant differences were observed between these two groups in terms of these outcomes. This discrepancy from the prior findings\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e may be due to the fact that, in our setup, the masks in M\u0026thinsp;+\u0026thinsp;T group were not required to be tightly sealed.\u003c/p\u003e\u003cp\u003eRegarding postoperative adverse events, no airway-related complications were noted in the THRIVE groups. There were no significant differences among the three groups in terms of overall adverse events. Nausea and vomiting occurred across all groups, likely attributable to anaesthetic agents and surgical stimulation, with no significant differences observed. Given the relatively short duration of THRIVE use in this study, potential airway injury from prolonged application was not evaluated.\u003c/p\u003e\u003cp\u003eThis study provides direct pressure data to validate stomach-related changes during mask ventilation induction, further supporting the link between mask ventilation and gastric insufflation, regurgitation, and aspiration. While THRIVE outperforms mask ventilation in reducing gastric insufflation, its limited CO₂ clearance capability should not be overlooked. Future research could explore a balanced preoxygenation method that addresses both issues.\u003c/p\u003e\u003cp\u003ePrevious studies have mostly focused on healthy patients. The data of intragastric pressure in obese patients provide valuable insights, laying a foundation for further research and adding evidence to support the application of THRIVE.\u003c/p\u003e\u003cp\u003e\u003cb\u003eLimitations\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe sample size of this study was relatively small, particularly among obese patients. The presence of outliers may have introduced significant variability into the dataset, potentially affecting the robustness of the study results.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eAdditionally, we did not further categorize the degree of overweight, with patients' BMIs ranging from just above 25 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e to over 35 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. Therefore, the effects of THRIVE on individuals with different degrees of overweight remain to be elucidated.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis randomized controlled trial demonstrates that THRIVE minimizes changes in intragastric pressure and provides superior oxygenation during anaesthesia induction in overweight patients. The THRIVE technique emerges as a practical and effective option compared with the current standard of mask ventilation.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003eTHRIVE\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eTransnasal Humidified Rapid Insufflation Ventilatory Exchange\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBMI\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eBody Mass Index\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePEtO\u003csub\u003e2\u003c/sub\u003e\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003epartial pressure of end-tidal oxygen\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSpO\u003csub\u003e2\u003c/sub\u003e\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eSaturation of Peripheral Oxygen\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePEtCO2\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003epartial pressure of end-tidal carbon dioxide\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eGERD\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003egastroesophageal reflux disease\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLES\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003elower esophageal sphincter\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFRC\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003efunctional residual capacity\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eERV\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eexpiratory reserve volume\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHFNC\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003ehigh-flow nasal cannula\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eECG\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eElectrocardiogram\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNIBP\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003enon-invasive blood pressure\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePCV\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003ePressure Controlled Ventilation\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTV\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eTidal volume\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePEEP:\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003ePositive End-expiratory Pressure\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCSAa:\u003c/strong\u003e Cross-sectional area of the gastric antrum\u003c/p\u003e"},{"header":"Declarations","content":"\u003col\u003e\n \u003cli\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThis prospective randomized controlled trial was approved by the Ethics Committee of the 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China (Approval No. KY2023-195; Chairperson: Professor Zimiao Chen) on 4 September 2023. The trial was prospectively registered at the China Clinical Trial Registration Center (Registration No. ChiCTR2300075652) prior to patient enrolment.\u003c/p\u003e\n\u003cp\u003eWritten informed consent was obtained from all participants or their legally authorized representatives before enrollment. Participants (or their proxies) were thoroughly informed of the study\u0026rsquo;s objectives, interventions, potential risks, benefits, and the right to withdraw at any time without affecting their clinical care.\u0026nbsp;All methods were carried out in accordance with relevant guidelines and regulations (Declaration of Helsinki)\u003c/p\u003e\n\u003col start=\"2\"\u003e\n \u003cli\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003col start=\"3\"\u003e\n \u003cli\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003col start=\"4\"\u003e\n \u003cli\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThe authors declare that they have no competing interests\u003c/p\u003e\n\u003col start=\"5\"\u003e\n \u003cli\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThis study received no external funding from any organization or institution.\u003c/p\u003e\n\u003col start=\"6\"\u003e\n \u003cli\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eCY: Study conceptualization and design, drafting the initial manuscript, and critical revision of the final manuscript.\u003c/p\u003e\n\u003cp\u003eYH: Experimental design and execution, data acquisition, and preliminary analysis.\u003c/p\u003e\n\u003cp\u003eTY: Literature review, data interpretation, and methodological optimization for data analysis.\u003c/p\u003e\n\u003cp\u003eSH: Statistical modeling, advanced data analysis, and validation.\u003c/p\u003e\n\u003cp\u003eZY: Critical revision of literature and development of the logical framework for result interpretation.\u003c/p\u003e\n\u003cp\u003eJQ: Key revisions to the methodology and discussion sections, academic compliance review.\u003c/p\u003e\n\u003cp\u003eMY: Overall study design oversight, quality control of experiments, and final manuscript approval.\u003c/p\u003e\n\u003cp\u003eLH: Cross-disciplinary resource coordination, ethics and funding compliance, and final manuscript approval.\u003c/p\u003e\n\u003col start=\"7\"\u003e\n \u003cli\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003col start=\"8\"\u003e\n \u003cli\u003e\u003cstrong\u003eAuthors\u0026apos; information (optional)\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCajander P, Edmark L, Ahlstrand R, Magnuson A, de Leon A. Effect of positive end-expiratory pressure on gastric insufflation during induction of anaesthesia when using pressure-controlled ventilation via a face mask: A randomised controlled trial. Eur J Anaesthesiol. 2019. 36(9): 625-632.\u003c/li\u003e\n\u003cli\u003eGreen SM, Mason KP, Krauss BS. Pulmonary aspiration during procedural sedation: a comprehensive systematic review. Br J Anaesth. 2017. 118(3): 344-354.\u003c/li\u003e\n\u003cli\u003eBouvet L, Albert ML, Augris C, et al. Real-time detection of gastric insufflation related to facemask pressure-controlled ventilation using ultrasonography of the antrum and epigastric auscultation in nonparalyzed patients: a prospective, randomized, double-blind study. Anesthesiology. 2014. 120(2): 326-34.\u003c/li\u003e\n\u003cli\u003eEl-Serag HB, Graham DY, Satia JA, Rabeneck L. Obesity is an independent risk factor for GERD symptoms and erosive esophagitis. Am J Gastroenterol. 2005. 100(6): 1243-50.\u003c/li\u003e\n\u003cli\u003ede Leon A, Th\u0026ouml;rn SE, Wattwil M. High-resolution solid-state manometry of the upper and lower esophageal sphincters during anesthesia induction: a comparison between obese and non-obese patients. Anesth Analg. 2010. 111(1): 149-53.\u003c/li\u003e\n\u003cli\u003eWu JC, Mui LM, Cheung CM, Chan Y, Sung JJ. Obesity is associated with increased transient lower esophageal sphincter relaxation. Gastroenterology. 2007. 132(3): 883-9.\u003c/li\u003e\n\u003cli\u003eJones RL, Nzekwu MM. The effects of body mass index on lung volumes. Chest. 2006. 130(3): 827-33.\u003c/li\u003e\n\u003cli\u003eCollet F, Mallart A, Bervar JF, et al. Physiologic correlates of dyspnea in patients with morbid obesity. Int J Obes (Lond). 2007. 31(4): 700-6.\u003c/li\u003e\n\u003cli\u003eDixon AE, Peters U. The effect of obesity on lung function. Expert Rev Respir Med. 2018. 12(9): 755-767.\u003c/li\u003e\n\u003cli\u003eSood A. Altered resting and exercise respiratory physiology in obesity. Clin Chest Med. 2009. 30(3): 445-54, vii.\u003c/li\u003e\n\u003cli\u003eMonro-Somerville T, Sim M, Ruddy J, Vilas M, Gillies MA. The Effect of High-Flow Nasal Cannula Oxygen Therapy on Mortality and Intubation Rate in Acute Respiratory Failure: A Systematic Review and Meta-Analysis. Crit Care Med. 2017. 45(4): e449-e456.\u003c/li\u003e\n\u003cli\u003eSztrymf B, Messika J, Bertrand F, et al. Beneficial effects of humidified high flow nasal oxygen in critical care patients: a prospective pilot study. Intensive Care Med. 2011. 37(11): 1780-6.\u003c/li\u003e\n\u003cli\u003eLodenius \u0026Aring;, Piehl J, \u0026Ouml;stlund A, Ullman J, Jonsson Fagerlund M. Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) vs. facemask breathing pre-oxygenation for rapid sequence induction in adults: a prospective randomised non-blinded clinical trial. Anaesthesia. 2018. 73(5): 564-571.\u003c/li\u003e\n\u003cli\u003ePatel A, Nouraei SA. Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE): a physiological method of increasing apnoea time in patients with difficult airways. Anaesthesia. 2015. 70(3): 323-9.\u003c/li\u003e\n\u003cli\u003eNi YN, Luo J, Yu H, et al. Can High-flow Nasal Cannula Reduce the Rate of Endotracheal Intubation in Adult Patients With Acute Respiratory Failure Compared With Conventional Oxygen Therapy and Noninvasive Positive Pressure Ventilation?: A Systematic Review and Meta-analysis. Chest. 2017. 151(4): 764-775.\u003c/li\u003e\n\u003cli\u003eWong DT, Dallaire A, Singh KP, et al. High-Flow Nasal Oxygen Improves Safe Apnea Time in Morbidly Obese Patients Undergoing General Anesthesia: A Randomized Controlled Trial. Anesth Analg. 2019. 129(4): 1130-1136.\u003c/li\u003e\n\u003cli\u003ePoobalan A, Aucott L. Obesity Among Young Adults in Developing Countries: A Systematic Overview. Curr Obes Rep. 2016. 5(1): 2-13.\u003c/li\u003e\n\u003cli\u003eHedenstierna G, Tokics L, Reinius H, Rothen HU, \u0026Ouml;stberg E, \u0026Ouml;hrvik J. Higher age and obesity limit atelectasis formation during anaesthesia: an analysis of computed tomography data in 243 subjects. Br J Anaesth. 2020. 124(3): 336-344.\u003c/li\u003e\n\u003cli\u003eGamal M, Mostafa M, Farrag Y, et al. Evaluation of adequacy of ventilation and gastric insufflation at three levels of inspiratory pressure for facemask ventilation during induction of anaesthesia: A randomised controlled trial. Anaesth Crit Care Pain Med. 2022. 41(5): 101132.\u003c/li\u003e\n\u003cli\u003eIsono S, Eikermann M, Odaka T. Facemask ventilation during induction of anesthesia: how \u0026quot;gentle\u0026quot; is \u0026quot;gentle\u0026quot; enough. Anesthesiology. 2014. 120(2): 263-5.\u003c/li\u003e\n\u003cli\u003eGroves N, Tobin A. High flow nasal oxygen generates positive airway pressure in adult volunteers. Aust Crit Care. 2007. 20(4): 126-31.\u003c/li\u003e\n\u003cli\u003eQian X, Hu Q, Zhao H, et al. Determination of the optimal inspiratory pressure providing adequate ventilation while minimizing gastric insufflation using real-time ultrasonography in Chinese children: a prospective, randomized, double-blind study. BMC Anesthesiol. 2017. 17(1): 126.\u003c/li\u003e\n\u003cli\u003eVan de Putte P, Perlas A. Gastric sonography in the severely obese surgical patient: a feasibility study. Anesth Analg. 2014. 119(5): 1105-10.\u003c/li\u003e\n\u003cli\u003eBouvet L, Mazoit JX, Chassard D, Allaouchiche B, Boselli E, Benhamou D. Clinical assessment of the ultrasonographic measurement of antral area for estimating preoperative gastric content and volume. Anesthesiology. 2011. 114(5): 1086-92.\u003c/li\u003e\n\u003cli\u003eJaber S, De Jong A, Schaefer MS, et al. Preoxygenation with standard facemask combining apnoeic oxygenation using high flow nasal cannula versuss standard facemask alone in patients with and without obesity: the OPTIMASK international study. Ann Intensive Care. 2023. 13(1): 26.\u003c/li\u003e\n\u003cli\u003eCoussa M, Proietti S, Schnyder P, et al. Prevention of atelectasis formation during the induction of general anesthesia in morbidly obese patients. Anesth Analg. 2004. 98(5): 1491-5, table of contents.\u003c/li\u003e\n\u003cli\u003eJeong JH, Kim DH, Kim SC, et al. Changes in arterial blood gases after use of high-flow nasal cannula therapy in the ED. Am J Emerg Med. 2015. 33(10): 1344-9.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Obesity, Anesthesia Induction, THRIVE, Intragastric Pressure, Oxygenation","lastPublishedDoi":"10.21203/rs.3.rs-6848070/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6848070/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\u003eAlthough many studies have shown that transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) can be used in anaesthesia induction, its specific effects on obese patients remain unknown.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe recruited 135 patients (BMI ≥25 kg/m²) who were randomly assigned to three groups: the facemask ventilation group (M group), the THRIVE group (T group), and the facemask with no ventilation combined THRIVE group (M+T group). Before induction, all patients underwent preoxygenation with a facemask until the partial pressure of end-tidal oxygen (PEtO\u003csub\u003e2\u003c/sub\u003e) exceeded 90%. After induction, a gastric intraluminal pressure catheter was inserted, and the catheter was connected to a disposable pressure transducer (in central venous pressure mode) via a three-way stopcock, with the calibration point located at the mid-axillary line. Subsequently, each group underwent different ventilation methods for 2 minutes before tracheal intubation and mechanical ventilation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere were no significant differences in initial intragastric pressure among the three groups. However, the peak intragastric pressure in the T and M+T groups was significantly lower than that in the M group (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). Within-group comparisons indicated no statistically significant differences between initial and peak intragastric pressures in the T and M+T groups. In contrast, the peak intragastric pressure during ventilation in the M group was significantly higher than its initial value (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). Fewer patients in the T and M+T groups demonstrated notable changes in gastric antral area on ultrasound compared with the M group (\u003cem\u003eP \u003c/em\u003e\u0026lt; 0.05). Additionally, the lowest SpO\u003csub\u003e2\u003c/sub\u003e and PEtO\u003csub\u003e2\u003c/sub\u003e in the T and M+T groups were significantly higher than those in the M group (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). However, the first complete respiratory waveform of PEtCO\u003csub\u003e2\u003c/sub\u003e after mechanical ventilation and the lowest PEtCO\u003csub\u003e2\u003c/sub\u003e within 2 minutes of mechanical ventilation were higher in the T and M+T groups than in the M group (\u003cem\u003eP \u003c/em\u003e\u0026lt; 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe use of THRIVE during the induction of anaesthesia in overweight patients, compared with conventional facemask preoxygenation, can improve oxygen saturation while ensuring minimal alterations in intragastric pressure.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrial registration: \u003c/strong\u003eChinese Clinical Trial Registry ChiCTR2300075652. Registered date: 12/09/2023\u003c/p\u003e","manuscriptTitle":"The Impact of Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE) on Intragastric Pressure During Anaesthesia Induction in Overweight Patients: A Randomized Controlled Trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-11 10:47:22","doi":"10.21203/rs.3.rs-6848070/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":"07769e4f-76dc-4f1f-8334-cdfd850c00d3","owner":[],"postedDate":"August 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-12T09:39:15+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-11 10:47:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6848070","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6848070","identity":"rs-6848070","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}