Prone positioning in ARDS-patients on ventilator. Effects on alveolar-arterial-oxygen-ratio.

Background: Lung injury in acute respiratory distress syndrome (ARDS) is characterized by increased permeability of the alveolar-capillary membrane, diffuse alveolar damage, and the accumulation of proteinacenous pulmonary edema. In several studies prone positioning has been shown to improve oxygenation in pasient with ARDS, due to reduced V/Q-shunting, increased functional recidual capacity and repositioning of the heart and diaphragm. Objective: The first study on prone positioning on ARDS-patients in an Norwegian ICU. We wanted to investigate whether prone positioning in these patients had improved their alveolar-arterial-oxygen-ratio. Design: A retropspective chart review of patients with ARDS treated with prone positioning during the period 2000-2002. Setting: ICU at Ullevål University Hospital. Patients: We studied 11 patients with a total of 29 interventions of turning to prone position. Measurements and main results: To monitor improvement of oxygenation we calculated the alveolar-arterial-oxygen-ratio based on arterial blood gas alterations and ventilator settings before, during and after turning prone. In 22 out of the 29 interventions, turning prone resulted in a reduction of the alveolar-arterial-oxygen-ratio(p=0,01). Discussion: Our study confirms what previous studies have shown, that prone positioning reduces the alveolar-arterial-oxygen-ratio in ARDS-patients and thereby improves oxygenation