The effect of lateral positions on gas exchange in patients with unilateral lung disease during mechanical ventilation.

Positional changes have long been known to have a gravitational effect on the distribution of pulmonary blood flow. The effect of body position, supine, right and left lateral decubitus, on gas exchange were evaluated in 10 patients with predominantly unilateral lung disease. All patients were treated with mechanical ventilation and PEEP. Arterial blood gases, measured after 15 min in each of the three positions, showed that lying on the side of the "normal" lung resulted in a higher arterial pO2 (mean: 144 mmHg) than lying on that of the "damaged" lung (mean: 86 mmHg). The delta AapO2 values were 334 to 391 mmHg. Both differences were statistically significant (p less than 0.005). No significant changes mean arterial carbon dioxide tensions were noted.