Effect of Pressure-Controlled Versus Volume-Controlled Ventilation on Gastric Insufflation During i-gel Use in...

Background and Objectives: Gastric insufflation may occur during positive-pressure ventilation through a supraglottic airway when airway pressure exceeds the seal pressure. Because pressure-controlled ventilation (PCV) lowers peak inspiratory pressure compared with volume-controlled ventilation (VCV), it is widely assumed to reduce gastric insufflation-an assumption that remains untested in adults. We therefore compared these two ventilation modes during i-gel ventilation. Materials and Methods: In this single-centre, assessor-blinded randomised controlled trial, 68 adults undergoing elective breast surgery under general anaesthesia with an i-gel and neuromuscular blockade, without a gastric drain tube, were allocated 1:1 to PCV or VCV (tidal volume 8 mL/kg of actual body weight). The primary outcome was the postoperative gastric antral cross-sectional area measured by ultrasonography, an indirect measure of gastric gas. The pre-specified primary analysis was a Student's t-test. Secondary outcomes included peak inspiratory pressure and oropharyngeal leak pressure; gastric insufflation, defined post hoc as a >30% increase in antral area, was assessed as an exploratory outcome. Results: All 68 participants (34 per group) were analysed. The postoperative antral cross-sectional area did not differ between groups (mean difference, PCV - VCV, -23.7 mm²; 95% CI -73.9 to 26.4; p = 0.347; p = 0.568 after adjustment for baseline); the confidence interval excluded the 100 mm² difference the trial was powered to detect. Gastric insufflation occurred in 2/34 (VCV) versus 3/34 (PCV) (p = 1.000). Peak inspiratory pressure and expiratory tidal volume were lower with PCV (all p ≤ 0.002), whereas oropharyngeal leak pressure was similar; in every patient, peak pressure remained below the leak pressure. No adverse events occurred. Conclusions: In adults ventilated through an i-gel at the low airway pressures this device produces, PCV lowered peak inspiratory pressure but did not reduce the postoperative antral cross-sectional area or the incidence of gastric insufflation compared with VCV. Because delivered tidal volume was also lower with PCV, the peak pressure difference is reported descriptively. Within this low-pressure range, and in this selected population, the ventilation mode did not detectably affect gastric insufflation; the trial does not establish equivalence between the modes or extend to higher airway pressures or obesity.