Effects of backrest elevation and position on pulmonary artery pressures.

This repeated measures study identified each subject's baseline range of fluctuation in pulmonary artery pressures and used this information to evaluate the effects of changes in backrest elevation (0 degrees and 30 degrees) and position (supine and lateral) on pulmonary artery pressures. Sixteen hemodynamically stable patients were studied. Six measures of pulmonary artery pressure were obtained with subjects in the supine (flat) position. Pulmonary artery systolic pressures fluctuated from 2-16 mm Hg, pulmonary artery diastolic pressures from 0-11 mm Hg, and pulmonary artery mean pressures from 0-13 mm Hg. Only pulmonary artery diastolic pressures were not altered in a statistically significant way with backrest elevation. Even though backrest elevation produced clinically significant changes (those exceeding the subject's baseline range of fluctuation) in some subjects, no other changes in parameters of hemodynamic status were observed. These results suggest that pulmonary artery pressures may be obtained with backrests elevated. Since position changes produced both statistically and clinically significant changes in all pulmonary artery pressures, the use of lateral positions during pulmonary artery pressure measurement is not recommended.