Deflationary phenomenon of the nitrous oxide-filled endotracheal tube cuffafter cessation of nitrous oxide administration

After cessation of nitrous oxide (N2O) administration intracuff pressure of the endotracheal tube may decrease through rediffusion of N2O. There may t hen be an increased risk for air leaks, aspiration of gastric contents, or both. In this study, the time required for intracuff pressure to decrease b y 50% (T-1/2) after substituting oxygen for N2O inspired was estimated with the least-squares method. Fifty patients were randomly assigned to five gr oups, and their tracheas were intubated with the Hi-Contour, Sheridan, Rush , Reinforce, or Profile Soft-Seal Cuff endotracheal tubes. Cuffs were infla ted with 40% N2O, and cuff pressure was measured during anesthesia with 67% N2O. After 120 min, N2O inspired was replaced with 100% oxygen, and cuff p ressure was measured until the cuff pressure decreased by about 30%. In the five groups, stable cuff pressures were achieved during 120 min of anesthe sia with N2O. The cuff pressures at 120 min were not different among groups (P = 0.098). After cessation of N2O administration, the intracuff pressure decreased exponentially. T-1/2 in the Hi-Contour group was 27.8 +/- 8.5 mi n, which was significantly shorter than in the Profile Soft-Seal Cuff group (49.7 +/- 18.5 min; P < 0.01). Therefore, our results demonstrate that pre ssure of the N2O-filled cuff decreases quickly when N2O-inspired concentrat ions are reduced, and we suggest that intracuff pressure should be checked frequently to avoid air leaks or aspiration of gastric contents during dela yed extubation or transportation of patients with tracheal intubations.