Prolonged endotracheal intubation may be complicated by tracheal wall lesions caused by the blocking cuff of the tube. This happens when the tracheal wall load exceeds the capillary perfusion pressure. It is therefore important to control this load. As direct measurement presents difficult methodological problems, there have been many attempts to approximate the pressure load using different formulae. In a model trachea we showed the significance of the tracheal wall pressure as approximated by an indirect measurement principle. Our investigations demonstrate that the examined indirect method provides a sufficient approximation of the tracheal wall load only if it is used with the new low pressure high volume cuffs. It fails if it is used with the customary high pressure low volume balloons.