Direct measurement of mucosal pressures exerted by cuff and non-cuff portions of tracheal tubes with different cuff volumes and head and neck positions

We measured directly mucosal pressures against the cuff and non-cuff portio ns of the tracheal tube in different head-neck positions and tested the rel iability of calculated mucosal pressures, in vivo intracuff pressures and c uff volume as determinants of directly measured mucosal pressures. We studi ed 10 anaesthetized, paralysed adult patients. An 8.5-mm, high volume, low pressure PVC tracheal tube was used. Microchip sensors were attached to thr ee cuff locations (anterior, lateral and posterior) and two non-cuff locati ons (anterior tip and anterior aspect of the tube, 5 cm proximal to the cuf f). Directly measured mucosal pressures, in vivo intracuff pressures and ca lculated mucosal pressures (in vivo minus in vitro intracuff pressures) wer e determined after brief inflation (<15 s) to 0, 5, 10 and 15 mi. In vivo i ntracuff pressures were then set at 30 mm Hg and the measurements repeated, first in the neutral position and then with the head-neck extended, flexed and rotated. Cuff mucosal pressures were highest anteriorly and lowest pos teriorly. Non-cuff mucosal pressures did not vary with cuff volume and were approximately 15 mm Hg. Compared with the neutral position, in vivo intrac uff pressures were higher in the rotated, extended and flexed positions. Co mpared with the neutral position, mucosal pressure increased on the anterio r aspect of the tube in the flexed position by 22 mm Hg (P=0.003), at the a nterior tip in the extended position by II mm Hg (P=0.002) and at the anter ior tip (5 mm Hg, P=0.05) and lateral aspect of the cuff (5 mm Hg, P=0.03) in the rotated position. In vivo intracuff pressures and calculated mucosal pressures were moderate predictors of measured mucosal pressures; cuff vol ume was a poor predictor. We conclude that tracheal mucosal pressures were highest anteriorly, that non-cuff portions of the tube exerted substantial mucosal pressures and that the rotated position caused a greater increase i n tracheal mucosal pressure than the extended or flexed position. Indirect methods of measuring mucosal pressure were of moderate predictive value.