Effects of supine and lateral positions on cardiac output and intracardiac pressures

In the hospitalized patient and during cardiac catheterization, cardiac output and intracardiac pressures are almost always measured with the subject in the supine position. There are limited and sometimes conflicting data on the effects of the left and right lateral positions on these variables. In nonpregnant human beings, some studies have shown the cardiac output to be higher in the supine than in the right or left lateral positions.^1,2 Others³ have reported that cardiac output is higher in the left lateral than in the supine or right lateral positions, whereas others have demonstrated no difference in output among these various positions.⁴ Recent studies in animals have shown that cardiac output is higher in the left and right lateral positions than when the animals are supine.⁵. There are no published studies in man reporting the effects of the supine and lateral positions on micromanometer-measured intracardiac pressures. In experimental animals, Nakao et al⁵ used micromanometer-tipped catheters and demonstrated that left and right ventricular peak systolic and end-diastolic pressures are higher in the left and right lateral positions than in the supine. No previously published study has examined left and right ventricular pressures in these various positions in man. Therefore, the present study was performed to assess the influence of the 90 ° left and right lateral positions on cardiac output and intracardiac pressures (measured with micromanometer-tipped catheters) in patients referred for elective cardiac catheterization.