Abstract
Regional difference of the amplitude of respiratory variations (Δp) in pulmonary arterial wedge pressure was investigated at different sites of the lung at various body positions in man and dogs. In 6 patients without pulmonary hypertension and 6 dogs, simultaneously measured Δp of wedge pressures in the right and left lungs was compared in supine, left lateral, right lateral and prone positions. The mean value of Δp of the left lung was always larger than the right one in any body positions. This was statistically significant except for right lateral and left lateral decubitus positions in man. In the other 5 dogs, Δp in the upper lung area and lower lung area in the right lung was compared in supine, head-up and head-down positions, and there was no statistically significant difference between the mean Δp in both wedge pressures in any body positions. No significant differences of the end-expiratory pulmonary arterial wedge pressures were found between the left and right lungs in different body positions in both patients and dogs and between upper and lower lung areas of the right lung in supine, head-up and head-down positions in dogs. The results suggest that the gravitational force does not cause regional difference of Δp of the wedge pressure, and it seems that significant difference of Δp between the left and right lungs is caused by the difference of the respiratory variations in intrathoracic pressure in both lungs.
