The effect of nitrous oxide diffusion on laryngeal mask airway cuff inflation in children.

We studied the effect of nitrous oxide (N2O) diffusion on size 2 LMA cuff inflation in 52 children, 38 +/- 21 months of age. LMA cuffs were inflated with air (Group A) or 65% N2O, oxygen and halothane (Group B). Cuffs were inflated in a stepwise manner, achieving a cuff leak pressure of 17 +/- 4 cm H2O for all patients. Cuff volume and intracuff pressure increased in Group A (8.5 +/- 1.0 ml to 10.8 +/- 1.4 ml and 101 +/- 36 mmHg to 152 +/- 42 mmHg, respectively) and decreased in Group B (8.9 +/- 1.0 ml to 6.6 +/- 1.5 ml and 90 +/- 30 mmHg to 53 +/- 37 mmHg, respectively). Cuff leak pressure did not change significantly in either group. We conclude that cuff inflation with a mixture of N2O/oxygen prevents N2O diffusion into the cuff, avoiding cuff overinflation without compromising LMA function.