Effect of Cuff Pressure Elevation on Internal Diameter of Tracheal Tube in Simulated Trachea.

Application of nitrous oxide during anesthesia causes an increase in tracheal tube cuff pressure over time. The purpose of this study was to investigate the effect of an increase in cuff pressure on 3 types of tube (the Portex, Mallinckrodt, and Parker) commonly used for nasotracheal intubation. A cylindrical vessel was used to simulate a trachea. Cuff pressure was set at 0 cmH2O (R0) or 20 cmH2O (R20) at room temperature, or at 20 cmH2O (H20), 40 cmH2O (H40), 60 cmH2O (H60), or 80 cmH2O (H80) in 38°C hot water and pressure applied for 30 min. The value obtained at R0 was used as a reference (100%) and the rate of change under each condition determined. No change was observed at R20 in any of the 3 groups. In 38°C hot water, internal diameter in the Portex group decreased by 5.4% at H20 and 7.3% at H40, while that in the Mallinckrodt group decreased by 6% at H40. No significant change was observed in internal diameter in the Parker group, even when cuff pressure was increased. The internal diameter in the Portex group was the smallest at all cuff pressures in hot water. When the nasotracheal intubation tubes selected were placed in a simulated trachea and cuff pressure increased, internal diameter in the Portex and Mallinckrodt groups decreased.