Determination of the Optimal Inspiratory Pressure to Decrease Incidence of Gastric Insufflation With Adequate Ventilation During Facemask Ventilation in Morbidly Obese Patients

Official title

Ultrasound-Guided Optimization of Inspiratory Pressure During Facemask Ventilation in Morbidly Obese Patients to Prevent Gastric Insufflation: A Randomized Clinical Trial

Overview

The goal of this randomized clinical trial is to optimize the inspiratory pressure during facemask ventilation (FMV) in morbidly obese patients (BMI ≥40 kg/m²), to ensure adequate ventilation while minimizing the risk of gastric insufflation by real-time ultrasound guidance

Detailed description

Morbid obesity, defined as a body mass index (BMI) ≥ 40 kg/m², presents significant challenges during the management of the airway and ventilation under general anesthesia. One of the critical issues is the increased risk of gastric insufflation during facemask ventilation (FMV), which can lead to pulmonary aspiration, reduced lung compliance, and impaired oxygenation. Therefore, optimizing inspiratory pressure to ensure adequate ventilation while minimizing the risk of gastric insufflation is paramount in this population.

Ultrasound imaging has emerged as a valuable, non-invasive tool for real-time assessment of gastric content and volume. Recent studies have demonstrated the utility of gastric ultrasonography in detecting gastric insufflation during positive pressure ventilation. By visualizing the antrum and measuring the cross-sectional area , anesthesiologists can identify even small volumes of air entering the stomach, which might not be clinically apparent.

Interventions

• Device "Ultrasound-Guided Optimization of Inspiratory Pressure During Facemask Ventilation"
  Description: Group A will be subjected to an inspiratory pressure of 10 cmH₂O. A curvilinear ultrasound probe will be placed in the epigastric region to visualize the antrum. Baseline gastric ultrasound will be performed to confirm an empty stomach. During FMV, ultrasound images will be obtained at 30, 60, and 90 seconds. Gastric insufflation will be detected by the change in gastric cross-sectional area (ΔCSA).
• Device "Ultrasound-Guided Optimization of Inspiratory Pressure During Facemask Ventilation"
  Description: Group B will be subjected to an inspiratory pressure of 15 cmH₂O. A curvilinear ultrasound probe will be placed in the epigastric region to visualize the antrum. Baseline gastric ultrasound will be performed to confirm an empty stomach. During FMV, ultrasound images will be obtained at 30, 60, and 90 seconds. Gastric insufflation will be detected by the change in gastric cross-sectional area (ΔCSA).
• Device "Ultrasound-Guided Optimization of Inspiratory Pressure During Facemask Ventilation"
  Description: Group C will be subjected to an inspiratory pressure of 20 cmH₂O. A curvilinear ultrasound probe will be placed in the epigastric region to visualize the antrum. Baseline gastric ultrasound will be performed to confirm an empty stomach. During FMV, ultrasound images will be obtained at 30, 60, and 90 seconds. Gastric insufflation will be detected by the change in gastric cross-sectional area (ΔCSA).
• Device "Ultrasound-Guided Optimization of Inspiratory Pressure During Facemask Ventilation"
  Description: Group D will be subjected to an inspiratory pressure of 25 cmH₂O. A curvilinear ultrasound probe will be placed in the epigastric region to visualize the antrum. Baseline gastric ultrasound will be performed to confirm an empty stomach. During FMV, ultrasound images will be obtained at 30, 60, and 90 seconds. Gastric insufflation will be detected by the change in gastric cross-sectional area (ΔCSA).

Primary outcome measures

• Incidence of Gastric insufflation (ultrasound-confirmed) during FMV [Time frame: At 30 seconds, 60 seconds, and 90 seconds after induction]

Secondary outcome measures (8)

• Tidal volume (mL/kg ideal body weight) and peak inspiratory pressure [Time frame: at 30, 60, and 90 seconds of facemask ventilation (FMV)]
• Oxygen saturation (SpO₂) [Time frame: At baseline and 30 seconds, 60 seconds, and 90 seconds during FMV]
• End tidal CO2 [Time frame: At baseline and 30 seconds, 60 seconds, and 90 seconds during FMV]
• Antral cross-sectional area [Time frame: at baseline (15 minutes before induction) and 30, 60, 90 seconds during FMV.]
• Heart rate [Time frame: At baseline, 30, 60, 90 seconds during facemask ventilation and one minute after endotracheal tube placement]
• Mean arterial blood pressure [Time frame: At baseline, 30, 60, 90 seconds during facemask ventilation and one minute after endotracheal tube placement]
• Hypoxia occurrence [Time frame: Monitored continuously from induction of anesthesia till one minute after endotracheal intubation]
• Aspiration events [Time frame: Continuously monitored, intraoperatively and postoperatively (24-hour follow-up).]

Eligibility criteria

Inclusion criteria

• Adult patients (18-65 years old) scheduled for elective surgery under general anesthesia requiring facemask ventilation.

• Morbid obesity (BMI ≥40 kg/m²).
• American Society of Anesthesiologists (ASA) physical status II-III.
• Normal upper gastrointestinal anatomy (no history of gastric surgery, esophageal strictures, or hiatus hernia).
• Fasted for at least 6 hours for solids and 2 hours for fluids (standard preoperative fasting guidelines).

Exclusion criteria

• • Emergency surgery (due to inability to ensure proper fasting or preoperative assessment).

• Known or suspected difficult airway (Mallampati class IV, limited neck mobility, or history of difficult intubation).
• Gastroesophageal reflux disease (GERD) or high aspiration risk (e.g., pregnancy, symptomatic hiatal hernia).
• Contraindications to facemask ventilation (facial trauma, beard/mask seal interference).
• Severe cardiopulmonary disease (e.g., severe COPD, pulmonary hypertension, or unstable angina).
• Neuromuscular disorders affecting respiratory function.
• Refusal to participate or inability to provide informed consent.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Double blind

Primary purpose

Prevention

Study locations

Egypt · 1 center

• Benha University Hospitals — Banhā

Identifiers

NCT: NCT07480031 · 3.7.2025

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗