The interrelations of the pulmonary arterial and venous wedge pressures.

APRESSURE recorded through a cardiac catheter wedged tightly in a small . pulmonary artery has been referred to as a "capillary," "venous" or "wedge" pressure. On the other hand, a pressure recorded through a cardiac catheter wedged into a pulmonary vein during thoracotomy and in intact animals has been referred to as a pulmonary venous wedge pressure'. Some investigators have found good correlation between the mean pulmonary arterial wedge pressure and the mean left atrial pressure in man and other animals; others have found great variability. A thorough analysis of the data and methods of each group of investigators reveals differences in technics with which the data were obtained, and in methods of statistical analyses. The purpose of this study was to show the relationship between pulmonary arterial wedge pressure and mean left atrial pressure on the one hand, and the pulmonary venous wedge pressure and mean pulmonary arterial pressure on the other. Determinations were made in normal dogs with the thorax open so that catheters could be placed precisely in the desired position.