The effect of positioning on hemodynamics and gas exchange in the critically ill: a review.

Positioning of critically ill patients affects hemodynamic and cardiopulmonary outcomes. A review of clinical studies indicates that backrest elevations up to 60 degrees do not affect measurement of intracardiac pressures or cardiac output, but PaO2 may diminish in sitting positions following surgical procedures. In lateral positions, measurement of intracardiac pressures and cardiac output is not recommended, since a uniform reference point has not been identified for lateral positions. In patients with unilateral lung disease, PaO2 increases with the unaffected lung in the dependent position. Despite widespread use, the Trendelenburg position has not been shown to provide consistent beneficial effects. Prone positioning may be beneficial in adult respiratory distress syndrome and in weaning of mechanically ventilated patients. When planning positioning maneuvers, critical care nurses should consider these effects in relation to the specific needs of each patient. Hemodynamic and cardiopulmonary responses to positioning should be evaluated in conjunction with other therapeutic modalities such as those designed to preserve skin integrity and improve comfort.