Effect of endotracheal tube lubrication on cuff pressure increase during nitrous oxide exposure: a laboratory and prospective randomized controlled trial

BACKGROUND: We previously demonstrated that lubrication of an endotracheal tube (ETT) cuff with K-Y™ jelly strongly and significantly inhibited the increase in cuff pressure during nitrous oxide (N(2)O) exposure in vitro. However, in our previous study, we identified critical differences between some influential factors, such as the amount of lubricant retained on the cuff, and studied temperature differences between laboratory and clinical conditions. Therefore, it remained unclear whether this effect holds true in clinical settings. METHODS: We first sought to study how changes in the amount of K-Y™ jelly and temperature influence the inhibitory effects of the lubricant on the increase in N(2)O-induced cuff pressure in vitro. Furthermore, we aimed to determine whether the application of K-Y™ jelly inhibits the increase in ETT cuff pressure during general anesthesia using N(2)O in adult patients. RESULTS: In the laboratory studies, we found that K-Y™ jelly inhibited the cuff pressure increase dose-dependently when the dose of K-Y™ jelly was varied (P = 0.02), and that such an inhibitory effect decreased with an increase in the studied temperature (P = 0.019). In the clinical study, lubrication with K-Y™ jelly slightly, but significantly, delayed the increase in ETT cuff pressure during general anesthesia with N(2)O (P = 0.029). However, the inhibitory effect in the clinical settings was smaller than that in vitro. CONCLUSIONS: Lubrication of the ETT cuff with K-Y™ jelly may delay the increase in cuff pressure during general anaesthesia with N(2)O. However, the clinical significance of this effect may be limited. TRIAL REGISTRATION: UMIN Clinical Trials Registry: UMIN000031377 on March 1, 2019.