# Effects of different ventilation modes on intra-abdominal pressure and postoperative nausea and vomiting during anesthesia: a single-blind, randomized controlled trial

## TL;DR

This study compares three ventilation methods during anesthesia to see how they affect stomach pressure and post-surgery nausea.

## Contribution

The study introduces a comparison of manual, pressure-controlled, and volume-controlled ventilation modes on intra-abdominal pressure and postoperative nausea during anesthesia.

## Key findings

- All three ventilation modes similarly reduced intra-abdominal pressure during anesthesia induction.
- Volume-controlled ventilation was associated with higher intra-abdominal pressure in patients with gastric insufflation.
- Pressure-controlled ventilation showed more stable tidal volume delivery and lower PaCO₂ levels.

## Abstract

Improper mask ventilation during anesthesia induction can inject air into the stomach, leading to gastric distension and elevated intra-abdominal pressure (IAP), thereby increasing the risk of reflux and pulmonary aspiration. This single-blind randomized controlled trial compared the effects of three mask ventilation modes—manual ventilation (MV), pressure-controlled ventilation (PCV), and volume-controlled ventilation (VCV)—on IAP during the induction period, and preliminarily observed the dynamic changes of IAP after endotracheal intubation and spontaneous breathing recovery, as well as the incidence of postoperative nausea and vomiting (PONV) in paralyzed patients. We hypothesized that there are differences in the effects of the three mask ventilation modes on IAP during the induction period: PCV may cause less disturbance to IAP than other modes due to its stable pressure control and adjustable tidal volume; meanwhile, IAP will show dynamic changes during the transition from mask ventilation to endotracheal intubation and after the recovery of spontaneous breathing. This hypothesis is based on the physiological mechanism that airway pressure transmission, thoracic-abdominal pressure gradient changes, and gastric distension during mask ventilation may affect IAP.

A total of 152 participants undergoing laparoscopic surgery were randomized into three ventilation groups, with airway pressure limited to 15 cmH₂O and tidal volume set at 6–8 mL/kg. IAP was measured indirectly via intravesical pressure. The primary outcome was the change in IAP at T0 (before induction) and T1 (after induction of anesthetics) during the mask ventilation period. The secondary outcomes included IAP at T2 (after tracheal intubation) and T3 (24 h after surgery), the incidence of gastric insufflation at T2, the antral cross-sectional area (CSA) at T0 and T2, the incidence and severity of PONV at T3, and hemodynamic and respiratory parameters at each time point.

IAP decreased in all three groups with no significant intergroup differences. However, within the VCV group, patients with gastric insufflation (GI+) showed higher IAP than those without (GI−) (p = 0.031). Peak airway pressure was also higher in GI + subgroups in both MV and VCV modes (p = 0.009 and p < 0.001, respectively). The PCV group exhibited greater delivered tidal volume and lower PaCO₂ (p < 0.001). There was no statistically significant difference in the incidence of postoperative nausea and vomiting (PONV) among the three groups, but the incidence of PONV in the gastric insufflation-positive (G+) subgroup was significantly higher than that in the negative (G-) subgroup (25.8% vs. 11.5%, p = 0.012). Other secondary outcomes did not differ significantly.

Although all three ventilation modes reduced IAP comparably during the mask ventilation period of anesthesia induction, gastric insufflation was associated with increased IAP within the VCV group. There was no significant difference in the incidence of gastric insufflation or IAP among the three ventilation modes. However, considering that the PCV group had more stable tidal volume delivery and lower PaCO₂, it may have potential advantages in maintaining respiratory stability during the induction period, which needs to be verified by further studies with larger sample sizes.

https://www.chictr.org.cn/showproj.html?proj=208066, identifier (ChiCTR2300076444).