Deflationary Phenomenon of the Nitrous Oxide-Filled Endotracheal Tube Cuff After Cessation of Nitrous Oxide Administration

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Abstract
After cessation of nitrous oxide (N(2)O) administration, intracuff pressure of the endotracheal tube may decrease through rediffusion of N(2)O. There may then be an increased risk for air leaks, aspiration of gastric contents, or both. In this study, the time required for intracuff pressure to decrease by 50% (T(1/2)) after substituting oxygen for N(2)O inspired was estimated with the least-squares method. Fifty patients were randomly assigned to five groups, and their tracheas were intubated with the Hi-Contour, Sheridan, Rush, Reinforce, or Profile Soft-Seal Cuff endotracheal tubes. Cuffs were inflated with 40% N(2)O, and cuff pressure was measured during anesthesia with 67% N(2)O. After 120 min, N(2)O inspired was replaced with 100% oxygen, and cuff pressure was measured until the cuff pressure decreased by about 30%. In the five groups, stable cuff pressures were achieved during 120 min of anesthesia with N(2)O. The cuff pressures at 120 min were not different among groups (P = 0.098). After cessation of N(2)O administration, the intracuff pressure decreased exponentially. T(1/2) in the Hi-Contour group was 27.8 +/- 8.5 min, 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 pressure of the N(2)O-filled cuff decreases quickly when N(2)O-inspired concentrations are reduced, and we suggest that intracuff pressure should be checked frequently to avoid air leaks or aspiration of gastric contents during delayed extubation or transportation of patients with tracheal intubations. A recently developed method for maintaining stable cuff pressure (N(2)O-filled cuffs) enables us to assess the decrease in cuff pressure after cessation of N(2)O administration. Our results confirm the limitations of N(2)O-filled cuffs when N(2)O-inspired concentrations are reduced.