The Effect of Positioning with Mechanically Ventilatory Acute Respitatory Failure Patients on Arterial Oxygen Partial Pressure and Alveolar-arterial Oxygen tension

Hwang, Hee Joung; Park, Hye Ja

Abstract

It is widely recognized that manipulation of body position takes advantage of the influences of gravity for improving oxygenation. The study aims to determine the effects of positioning(supine, prone, right lateral decubitus and left lateral decubitus positions) applied to the mechanically ventilatory acute respiratory failure patients on arterial oxygen partial pressure(PaO2), alveolar arterial oxygen tension difference(AaDO2), mean aterial pressure, peak inspiratory pressure and plateau pressure. Thirty two acute respiratory failure patients admitted to the medical intensive care unit at Kangnam St. Mary's Hospital, The Catholic University of Korea from March 1997 to January 1998, were divided into three groups by radiographic evidence of unilateral or bilateral lung disease. In group 1 with dominant right lung disease were twelve subjects, group 2 with dominant left lung disease had eight subjects and group 3 had twelve subjects with bilateral lung disease. The variables were measured in 30 minutes after each position of supine, prone, good lung down lateral decubitus and sick lung down lateral decubitus position. The position order was done at random by Latin squre design. The results are as follows; 1) With group 1 patients, the PaO2 in the left lateral decubitus and prone position were 126.8+/-30.8 mmHg and 106.7+/-36.8 mmHg, respectively(p=0.0001). 2) With group 2 patients, the PaO2 in the prone and the right lateral decubitus position were 121.7+/-44.7 mmHg and 118.5+/-31.7 mmHg, respectively (p=0.0018). 3) With group 3 patients, the PaO2 was 143.6+/-36.6 mmHg in the prone position (p=0.0001). 4) With group 1 patients, the AaDO2 in the left lateral decubitus and the right lateral decubitus position were 178.1+/-29.7 mmHg and 233.1+/-24.4 mmHg, respectively(p=0.0001). 5) With group 2 patients, the AaDO2 in the prone and the left lateral decubitus postion were 184.0+/-39.5 mmHg and 231.0+/-23.9 mmHg, respectively(p=0.0019). 6) With group 3 patients, the AaDO2 in the prone and the supine postion were 377.1+/-35.6 mmHg and 435.7+/-13.1 mmHg, respectively (p=0.0001). 7) There were no differences among the mean arterial pressure, peak inspiratory pressure and plateau pressure for each of the supine, prone, left lateral decubitus and right lateral decubitus position. The results suggest that oxygenation may improve in mechanically ventilatory patients with unilateral lung disease when the position is good lung dependent and prone, and patients with bilateral lung disease when the position is prone without any effects on the mean arterial pressure and airway pressure. It is suggested that body positions improve ventilation/perfusion matching and oxygenation need to be specified in patient care plans.