# Comparing the effect of three levels of end-expiratory pressure during facemask ventilation on gastric insufflation in patients with obesity: a randomized controlled trial

## TL;DR

This study found that higher end-expiratory pressure during face-mask ventilation increases gastric insufflation in obese patients, while lower pressure levels are safer.

## Contribution

The study is the first to compare three end-expiratory pressure levels and their impact on gastric insufflation in obese patients under anesthesia.

## Key findings

- High PEEP (8 cmH2O) significantly increased gastric insufflation compared to ZEEP and low PEEP.
- ZEEP and low PEEP showed similar and lower rates of gastric insufflation.
- Gastric insufflation occurred in all groups, but was most severe with high PEEP.

## Abstract

We compared the effect of three levels of end-expiratory pressure on the incidence of gastric insufflation during face-mask ventilation in patients with obesity.

This randomized controlled trial included adult obese patients undergoing elective non-cardiac surgery under general anesthesia with neuromuscular blockade. Patients were randomized to receive either zero-end-expiratory pressure (ZEEP group), 4-cmH2O positive end-expiratory pressure (PEEP) (low-PEEP group), or 8-cmH2O PEEP (high-PEEP group) during volume-controlled mask ventilation. Gastric antral cross-sectional area (CSA) was assessed using ultrasonography before induction of anesthesia and after intubation. The percentage of change (delta) in the CSA was calculated and gastric insufflation was considered significant when the delta CSA was > 30%. The primary outcome was the incidence of gastric insufflation. Secondary outcomes were antral CSA before induction of anesthesia and after intubation in addition to ventilatory variables (end-tidal CO2, peak airway pressure, and tidal volume) during face-mask ventilation.

We analyzed data from 160 patients. The antral CSA increased after intubation in all groups. The incidence of gastric insufflation was higher in the high-PEEP group (32/54[59%]) than that in the ZEEP group (6/52[12%]) and low-PEEP group (15/54[28%]). Delta CSA, antral CSA after intubation, and incidence of gastric insufflation were not significantly different between the ZEEP and low-PEEP groups. Ventilatory variables were comparable between the groups.

In obese paralyzed patients, gastric insufflation can occur during face-mask ventilation whatever the level of end-expiratory pressure; however, the use of ZEEP or 4-cmH2O PEEP was associated with lower incidence of gastric insufflation compared to 8-cmH2O PEEP.

Clinical trial registration at clinicaltrials.gov NCT05979129. https://classic.clinicaltrials.gov/ct2/show/NCT05979129