Laboratory evaluation of low-pressure tracheal tube cuffs: large-volume v. low-volume.

Large- and low-volume low-pressure tracheal tube cuffs were compared during exposure to nitrous oxide. The compliance of both types of cuff when measured inside and outside an artificial rigid trachea, the volume of intubated cuff, the residual volume, the nitrous oxide diffusion time, and the specific diffusion rate of the cuff membrane to nitrous oxide were measured in the laboratory. From these variables, the diffusion rate of nitrous oxide, the surface area available for nitrous oxide diffusion, the tracheal wall pressure exerted by cuff, and the degree of folding of the intubated cuff were derived. The results showed that the rapid increase in pressure of the large-volume cuff when intubated was caused by low compliance, the large surface area available for nitrous oxide diffusion, and the considerable permeability of the cuff membrane to nitrous oxide.