Comparison of central venous, oesophageal and mouth occlusion pressure with water-filled catheters for estimating pleural pressure changes in healthy adults.

The validity of the central venous and water-filled oesophageal catheter technique as a measure of pleural pressure changes was tested in ten healthy subjects in different body positions during inspiratory efforts with occluded airways, by comparing the simultaneous changes in mouth pressure (delta Pm) taken to represent pleural pressure changes, in central venous pressure (delta Pcv) and in oesophageal pressure (delta Poes). delta Pcv/delta Pm values were close to unity in the sitting and left lateral positions, whereas in the supine and right lateral position, substantial deviations from unity were found in some instances. delta Poes/delta Pm values were close to unity in all positions, except some rare instances. No appreciable phase difference between delta Pm/delta Poes and delta Pm/delta Pcv was found when the amplitude ratios were close to unity. We conclude that valid measurements of pleural pressure changes can be obtained in most instances with the central venous and the water-filled oesophageal catheter system according to the occlusion test procedure.