Repeated Deflation of a Gas-Barrier Cuff to Stabilize Cuff Pressure During Nitrous Oxide Anesthesia

Although a nitrous oxide (N(2)O) gas-barrier cuff effectively limits the increase of cuff pressure during N(2)O anesthesia, there are few data assessing whether an N(2)O gas-barrier cuff is more beneficial for stabilizing intracuff pressure than standard endotracheal tubes when cuffs are repeatedly deflated to stabilize pressure during N(2)O anesthesia. In the present study, the pressure of air-filled standard-type cuffs (Trachelon; Terumo, Tokyo, Japan) and N(2)O gas-barrier type endotracheal tube cuffs (Profile Soft-Seal Cuff [PSSC]; Sims Portex, Kent, UK) was measured during 67% N(2)O anesthesia (n = 8 in each), during which the cuffs were repeatedly deflated every 30 min (Trachelon) or 60 min (PSSC) for the first 3 or 4 h. After aspirating the cuffs for 3 h, the cuff pressure exceeded 22 mm Hg in more than half of the patients in both groups. However, aspiration of the cuffs for 4 h decreased the maximal cuff pressure between deflation intervals in both groups (P < 0.01 for each), and increased the intracuff N(2)O concentration (P < 0.0001 for each). After deflating the cuffs over 4 h, the cuff pressure in both groups never exceeded 22 mm Hg during the subsequent 3 h, and intracuff N(2)O concentrations did not significantly change. Therefore, deflation of cuffs for 4 h during N(2)O anesthesia sufficiently stabilized cuff pressure and equilibrated the intracuff N(2)O concentrations in both groups. The use of the PSSC endotracheal tube might be more practical because of the smaller number of cuff deflations required, but the PSSC does not reduce the duration of cuff deflations to stabilize the pressure.