Effects of the 30-degree lateral recumbent position on pulmonary artery and pulmonary artery wedge pressures in critically ill adults

Abstract

A common therapeutic nursing intervention is patient positioning. Despite demonstrated benefits of lateral positioning, critically ill patients may require prolonged supine positioning in order to obtain reproducible hemodynamic measurements. The rationale for supine positioning is based on research that suggests that pulmonary artery (PA) pressure measurements in the lateral and supine positions are different. However, this research was limited by the lack of an angle-specific left atrial (LA) reference, which may have introduced systematic measurement error. It was unknown if PA pressure measurements in the 30-degree lateral position, using an angle-specific LA reference, were similar to supine measurements.To determine the effect of 30-degree right and left lateral positions on PA and PAW pressures in critically ill adults, 35 post-cardiac surgery patients, aged 27 to 89 (mean 63.6 $\pm$ 11 years) were positioned in supine, right- and left-lateral positions. The patients served as their own controls. PA and PAW pressures were measured in each position.Data analysis included analysis of variance for repeated measures, post-hoc paired t-tests, and comparison to baseline pressure fluctuations. On average, PAS, PAED and PAM pressures in the left-lateral position were significantly different (p $<$.05) from supine pressures. The largest position-related pressure difference occurred in the PAS (2.0 $\pm$ 2.1 mm Hg), while the maximum PAED and PAW pressure differences were 1.4 $\pm$ 2.7 mm Hg and 1.6 $\pm$ 2.4 mm Hg, respectively. Clinically significant position-related pressure changes occurred in 12 of 581 pressure-pairs (2.1%). The changes occurred in six patients. Two patients had significant PAED pressure changes (five pressure-pairs, four attributed to one patient). Only one patient had a clinically significant change in PAW pressure. There were no demographic or clinical characteristics that differentiated between patients with and without significant pressure changes.This was the first large study of the effect of 30-degree lateral position with no backrest elevation on PA and PAW pressures, using a validated LA reference point. Results indicate that in hemodynamically stable cardiac surgery patients during the first 24 postoperative hours, PA and PAW pressures measured in the 30-degree lateral and supine positions are interchangeable.