Pulmonary circulatory adaptation to acute atelectasis in man.

Pulmonary functional veno-arterial shunt determinations were made breathing 100% oxygen in thirty consecutive patients during thoracotomy with one-lung anesthesia. Initially, with both lungs ventilated (FiO2 100%), the mean shunt value was 18.1 +/- 1.2% (S.D.). With the collapse of one lung by deflation and surgical pneumothorax, the shunt rose to 36.0 +/- 1.5%. With time the value fell: 36.0 +/- 1.5% at five minutes, 30.3 +/- 1.4% at fifteen minutes, 30.3 +/- 1.4% at thirty minutes, 28.1 +/- 1.4% at sixty minutes, and 24.6 +/- 2.8% after two hours. This trend was significant at a p value of less than 0.001. This study for the first time documents in man the phenomenon of pulmonary circulatory adaptation to acute atelectasis.