Mechanical ventilation in the prone position for acute respiratory failure after cardiac surgery.

Ten patients with acute respiratory failure (ARF) after coronary artery bypass grafting were studied during conventional mechanical ventilation in the supine and in the prone position. Impaired gas exchange was defined as an inspired oxygen fraction (FIO2) greater than 0.5 to maintain an arterial oxygen tension (PaO2) > or = 70 mmHg, an alveolar-arterial PaO2 gradient (PA-aO2) > 200 mmHg and a venous admixture (QVA/QT) > 15% during mechanical ventilation with a tidal volume (VT) = 10 to 12 mL/kg, frequency (f) = 10 to 15 VT/min, inspiratory-expiratory (I:E) ratio = 0.