Effect of body position upon pulmonary artery and pulmonary capillary wedge pressures in noncritically ill patients.

Monitoring pulmonary artery (PA) and pulmonary capillary wedge (PCW) pressures with a Swan-Ganz catheter to detect left ventricular failure has assumed an important role in the present day management of critically ill patients. In order to obtain an accurate reading, it has been assumed that the patient must be supine and flat. This may require waking an acutely ill patient; also there are patients who cannot tolerate a flat position. The effect of position upon the PA and PCW pressures was investigated in ten cardiac out-patients who were undergoing hemodynamic studies during exercise tolerance testing. The pressures were measured with the backrest flat, then at 20 degrees, 45 degrees, and 90 degrees and with patient sitting on edge of bed with feet dangling. The only significant difference with relation to position was systolic pressure at 90 degrees in relation to the systolic pressure in the flat position. Other pressure differences were not statistically significant and all pressure differences were of such small magnitude as not to be clinically significant. Based on these findings, it would seem that in patients with normal PA pressures, measurements can be made without lowering the backrest. Further study is needed to determine the effect of position on these pressures in critically ill patients.