The effect of lateral positions on gas exchange in pulmonary disease. A prospective evaluation.

Abstract

The effects of body position, supine and right and left lateral decubitus positions, on arterial blood gases were evaluated in 7 hospitalized and 31 ambulatory patients with lung disease. Arterial blood gases were analyzed 15 minutes after a new position was assumed with the subjects breathing room air or various fractions of inspired oxygen (F102) to FIo2 = 1.0. Similar studies were performed in 6 normal volunteers, the control group. Significant difference in arterial oxygen tension (Pa02) values between positions were found for patients but not for control subjects. When the arterial blood gases in a given patient were evaluated in relation to the radiographic distribution of disease, it became clear that when disease was pre­ dominantly or exclusively confined to one lung or hemithorax, lying on the opposite healthy lung resulted in higher Pa02 values (mean: 85 mm Hg) than lying on the sick lung (mean: 77 mm Hg). With disease equally distributed (radiographically) to both lung fields, Pa02 values were higher lying on the right side (mean: 84 mm Hg) than on the left side (mean: 79 mm Hg). This difference was possibly due to cardiac compression of the left lung or the smaller volume of the left lung. In 6 patients in whom there was no radiographic evidence of disease, Pa02 values were not different right-side down (mean: 93 mm Hg) and left-side down (mean: 94 mm Hg). Because the magnitude of the differences in Pa02 values between different decubitus positions for a given patient were usually considerable (mean: 9.7 mm Hg; range: 0 to 67 mm Hg), clinical applications of the data may be therapeutically helpful.