Preoperative pulmonary blood flow and one-lung anaesthesia.

The distribution of pulmonary blood flow was measured in supine patients before surgery by means of lung perfusion scanning with 99mTc-macroaggregated albumin in an attempt to predict values of PaO2 during subsequent one-lung anaesthesia. The PaO2 values during one-lung anaesthesia were well correlated with the preoperative lung perfusion partition ratios (r = 0.84, p less than 0.05). In 9 of 40 patients, PaO2 was less than 80 mmHg during one-lung ventilation (FIO2 0.99). In these patients the lung perfusion ratios of the dependent lung were as low as 41.0-48.2 per cent. These results indicate that preoperative measurement of pulmonary blood flow can predict values of PaO2 during one-lung anaesthesia.