Pressure vs. volume control ventilation: effects on gastric insufflation with size-1 LMA

In this randomized prospective study, peak airway pressure (PAP) and gastric insufflation were compared between volume control ventilation (VCV) and pressure control ventilation (PCV) using size-1 laryngeal mask airway (LMA) in babies weighing 2.5-5 kg.

Forty ASA I and II children, weighing 2.5-5 kg, undergoing elective infraumbilical surgeries (duration < 60 min) were randomized to two groups of 20 each to receive either PCV or VCV. Patients at risk of aspiration, difficult airway and upper respiratory tract infection, and poor lung compliance were excluded. Anesthesia technique included sevoflurane/O(2)/N(2)O without neuromuscular blockade. PAP in PCV and tidal volume in VCV modes were changed to achieve adequate ventilation (P(E)CO(2) of 5-5.4 kPa). PAP was maintained below 20 cm H(2)O. Chi-squared test, Mann-Whitney U-test and Wilcoxon W-test were applied; P < 0.05 was considered significant.

Mean PAP (cm H(2)O) was 12.2 ± 1.09 in PCV and 13.60 ± 0.94 in VCV groups (P = 0.000). The confidence interval of mean difference of PAP varied from 0.79 to 2.10. Significant increases in abdominal circumference were observed in both groups: PCV: 0.94 ± 1.04 cm and VCV: 2.2 ± 1.3 cm; (P = 0.000). The SpO(2) and hemodynamic variables did not differ between the groups. One patient in VCV group (with PAP = 14 cm H(2)O) could not be ventilated to the target P(E)CO(2), and the LMA had to be replaced with tracheal tube.

In conclusion, PCV should be the preferred mode to provide positive pressure ventilatio (PPV), when using the size-1 cLMA in babies weighing 2.5-5 kg, in view of less gastric insufflation associated with it for surgeries of brief duration. More studies are required to validate the clinical significance of these two modes of ventilation in longer procedures, in this subpopulation.