Differential ventilation in acute bilateral lung disease. Influence on gas exchange and central haemodynamics.

Eight patients with acute respiratory failure (ARF) due to diffuse and rather uniform lung disease were intubated with a double-lumen bronchial tube and ventilated in the lateral decubital position by two synchronized ventilators. Ventilation of each lung was individually adjusted to match the expected regional blood flow (differential ventilation). When ventilation with equal volumes (i.e. 50% of tidal volume to each lung) was performed, a 19% reduction of venous admixture (P less than 0.001) and a 22% increment in arterial oxygen tension (P less than 0.001) were seen. Comcomitantly, the cardiac output increased by 17% (P less than 0.001), to which a reduced pulmonary vascular resistance may have contributed. The net result was a 14% increment of the oxygen availability (P less than 0.001). An attempt to go further, giving 2/3 of the tidal ventilation to the dependent lung, was made on six of the patients. However, this ventilatory pattern did not further improve the gas exchange and also had detrimental effects on the haemodynamics. It is concluded that differential ventilation with equal tidal volumes in the lateral position can substantially improve gas exchange and central haemodynamics in patients with ARF due to diffuse lung disease.