Tracheal tube cuff pressure--study on tube size and inflating gases

The effect of nitrous oxide on the cuff pressure was studied from the following points of view. One was the size of tubes and the type of cuff. The other was the effects of different gas mixture in the cuff. The changes of the cuff pressure were investigated using four types of tubes such as the largest standard cuffed tube which could be passed through the glottis, the 1.0 mm less in I.D. standard cuffed tube, the largest profile cuffed tube, and the 1.0 mm less in I.D. profile cuffed tube. There was no difference between the profile cuffed tube groups but in the standard cuffed tube groups, the cuff pressure increased from the beginning in 1.0 mm less I.D. tube group. Air, inhalation anesthetic gas (nitrous oxide:oxygen = 3:2) and mixtured gas (inhalation anesthetic gas and air = 4:3) were used to inflate the cuff. The cuff pressure was measured at the same patients. In the group of anesthetic gas, the cuff pressure decreased and in some cases, there occurred a leakage of gas. In the group of air, the cuff pressure increased as well as experiment I. However in the group of mixtured gas, there were almost no changes in the cuff pressure. This means that if the cuff is inflated with a mixtured gas in which nitrous oxide is under the equivalent condition, the cuff pressure would not change.