Optimising peak inspiratory pressures during induction of Anaesthesia: Comparing gastric inflation with 15 and 20 cm H2O during facemask ventilation using ultrasonography

Introduction

Pulmonary aspiration of gastric contents is a major cause of mortality related to general anaesthesia. This study examines the effects of lower peak inspiratory pressures (15 cmH₂O) on gastric inflation (GI) and ventilation adequacy compared to the current accepted cutoff of 20 cmH₂O.

Methods

In this comparative, randomised study, patients were allocated to two groups, P15 and P20, defined by the peak inspiratory pressures during 3 min of pressure-controlled facemask ventilation (FMV). Anaesthesia was induced using propofol and fentanyl, along with neuromuscular blockade using vecuronium. Using ultrasonography, the cross-sectional area (CSA) of the gastric antrum was measured, and arterial blood gas samples were taken at baseline and the end of 3 min of FMV. The left paratracheal oesophagus on-air entry (LPEOAE) was also visualised during the FMV using ultrasonography.

Result

Sixty patients were analysed. The authors registered statistically significant inflation in both groups after 3 min of FMV (p < 0.001). However, at the end of FMV, it was significantly greater in the P20 (p = 0.009). Arterial blood gas analysis revealed adequate oxygenation and ventilation in both groups. LPEOAE was significantly higher in the P20 group (p = 0.039). No significant changes in hemodynamics were seen in the two groups.

Conclusion

Lower inspiratory pressures of 15 cmH₂0 resulted in a reduced gastric inflation while providing adequate ventilation and oxygenation during the induction of anaesthesia in paralysed, non-obese patients.