Measurement of tracheal wall pressure: a comparison of three different in vitro techniques.

We compared three different tracheal wall pressure measuring techniques in vitro. Using a high-volume, low-pressure, cuffed tracheal tube with an internal diameter of 7.5 mm and a model trachea, the pressure difference technique, the wall pressure membrane technique and the microchip sensor probe technique with and without lubrication were studied. Wall pressures were measured after sequential injections of 0.5 ml of air into the cuff at cuff pressures ranging from 0 to 50 mmHg. The coefficient of variance was largest for the microchip sensor probe technique with lubrication (29%) and without lubrication (214%), and was lower for the wall pressure membrane technique (22%) and the pressure difference technique (19%). The wall pressure membrane and pressure difference techniques provided comparable results. The microchip sensor probe technique considerably underestimated wall pressure. These findings have an impact on the interpretation of published data on tracheal or pharyngeal wall pressure using the microchip sensor probe technique.