Pulmonary arterio-venous fistula. A shunt equation exercise during thoracotomy.

A report is given of a patient with multiple bilateral pulmonary arterio-venous fistulae who underwent right thoracotomy for this condition. Blood-gas studies before and during surgery showed that the arterio-venous oxygen content differences of 1-16-1-34 mmol/l were less than normal, and the calculated venous admixture during the procedure varied from 44 to 60% of cardiac output. The changes in venous admixture at various stages of the operation could not be predicted on the basis of evidence derived from normal lungs.