The influence of the pulmonary arterial pressure on the pulmonary capillary venous pressure in man.

In two cases with a well-defined pulmonary capillary venous pressure pulse, the lobular pulmonary artery was occluded with a balloon while the pulmonary capillary venous pressure was registered. There was no change in the tracing obtained. In two other cases positive pressure respiration almost completely damped out the pulmonary capillary venous pressure variations, but the mean pressure remained virtually unchanged. It is concluded that the pulmonary arterial pulse wave usually does not cause artefacts in the pulmonary capillary venous tracing. Cyclic changes in pulmonary capillary venous pressure cannot be studied while the subject is on positive pressure respiration.