Ventilation and arterial oxygenation during thoracic surgery.

Considerable interest has been shown in recent years in the relative distributions of alveolar blood and gas flows under various conditions. During thoracic surgical procedures in the lateral position, with one hemithorax open and with controlled ventilation of the lungs, a severe degree of maldistribution of blood and gas may be expected. The upper lung may be freely expanded, retracted by the surgeon, or deliberately deflated by the anaesthetist. The purpose of this study is to confirm changes in the distribution of inspired gas at various stages of intrathoracic operations and to observe the effects, if any, these changes have on the composition of the arterial blood.