Effect of backrest position on hemodynamic and right ventricular measurements in critically ill adults

Hemodynamic measurements are often obtained with the patient in a flat, supine position. Reports suggest that these measurements can be reliably obtained at backrest elevations from 0 degree to 45 degrees. However, no study has been performed to evaluate the effects of position change on all the measurements that can be obtained via a pulmonary artery catheter.

To investigate the effects of backrest elevation of 0 degree, 30 degrees, and 45 degrees on measurements obtained via a pulmonary artery catheter.

Thirty-nine patients in an ICU at a university-based hospital, who required a pulmonary artery catheter, were studied. A single-group, repeated-measures design was used. Hemodynamic and volumetric measurements were obtained from all subjects.

Repeated-measures analysis of variance revealed that differences in cardiac index were statistically significant, and differences in cardiac output approached statistical significance. However, examination of the means of these measurements indicates a clinically nonsignificant difference in these values. No statistically or clinically significant differences were found for the other hemodynamic or volumetric measurements studied related to the order of backrest elevation.

Findings support the hypothesis that a patient need not be placed flat to obtain accurate hemodynamic and volumetric measurements. Results of this study are consistent with those of previous research and extend previous results to include the volumetric measurements of end-diastolic volume index and right ejection fraction. In addition, the use of mechanical ventilation and vasoactive drugs did not alter the accuracy of the measurements at backrest elevations from 0 degree to 45 degrees.