Effect of nitrous oxide on intracuff pressure of the ProSeal laryngeal mask airway

Objective To investigate the effect of nitrous oxide on the intracuff pressure of ProSeal laryngeal mask airway(PLMA) and intervention measures during anesthesia.Methods Sixty ASA class ⅠorⅡ patients undergoing elective operations were randomized into four groups.PLMA cuffs were inflated to 20 mm Hg as initial pressure with air(group A and D),50% N2O(group B) and saline(group C).50% N2O with isoflurane and propofol were used to maintain anesthesia.During operation the intracuff pressure was monitored in all patients.When the intracuff pressure came to 40 mm Hg in group D,we deflated cuff to the initial pressure.Postoperative airway complications were recorded.Results The intracuff pressure significantly increased in group A while it remained stable in group B and group C(P0.05).The first cuff deflation for group D was at(20±7) min.The intracuff pressure was lower in group D than that in group A by cuff deflation for 1 or 2 times(P0.05).Blood contamination on PLMA after removal was more common in group A than that in group B(P0.05).There was no significant difference in the incidence of sore throat,dysphagia and dysphonia among the four groups.Conclusion Nitrous oxide diffusion into PLMA increases the cuff pressure.Inflation of the cuff with the inspired gas mixture of N2O/oxygen,saline or cuff deflation during anaesthesia can prevent the increase of intracuff pressure.