• Takahisa Goto, Sayaka Tsuboi, Tetsuya Miyashita, Yoshiko Yamamoto, and Kentaro Sakamaki.
• Department of Anesthesiology, Yokohama City University Hospital, Yokohama, Japan, 3-9 Fukuura, Kanazawa-ku, Yokohama, Kanagawa 236-0004, Japan.
• Anesth. Analg.. 2013 Mar 1;116(3):609-12.

BackgroundStudies have compared sealing effects of the newly developed tapered endotracheal tube cuff with the conventional cylindrical cuff. In this study, we compared the difference between cuffs with regard to the increase in intracuff pressure during nitrous oxide (N(2)O) exposure.MethodsTwo types of cuffs were studied using a model trachea connected to a mechanical test lung: high-volume, low-pressure cuff (Mallinckrodt Hi-Lo(TM), Covidien, Dublin, Ireland) and tapered cuff (Mallinckrodt TaperGuardTM, Covidien). The intracuff pressure was set at 20 cm H(2)O, and the increase in pressure was measured during mechanical ventilation using 66% N(2)O. Intracuff pressures were recorded after 5, 10, 15, 30, 45, and 60 minutes of exposure to N(2)O.ResultsThe intracuff pressure recorded during the first 15 minutes of N(2)O exposure in high-volume, low-pressure cuffs was significantly higher than tapered cuffs (2-way repeated-measures analysis of variance, P < 0.0001 for internal diameters [IDs] 7.0 and 7.5 mm, P = 0.0004 for ID 8.0 mm, P = 0.0013 for ID 8.5 mm), and there were also statistically significant differences regarding interaction of time and cuff type (P < 0.0001 for IDs 7.0, 7.5, 8.0, and 8.5 mm). The difference in mean cuff pressures among groups after 10 minutes of N(2)O exposure was -18.5 (SE, 1.4; 99% confidence interval, -22.8 to -14.2; P < 0.0001) for ID 7.5 mm. Tapered endotracheal tube cuffs sealed the trachea with fewer dimples on the carina side of the cuff. Dimples on the cuff surface probably increase the surface for N(2)O diffusion. Therefore, fewer dimples result in a smaller surface area through which N(2)O can diffuse.ConclusionDuring general anesthesia with N(2)O, the intracuff pressure of tapered endotracheal tube cuffs did not increase as rapidly as it did in conventional high-volume, low-pressure cuffs. The pressure in both types of cuffs increased rapidly when exposed to 66% N(2)O, and hence continuous or frequent monitoring is recommended.

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