Pulmonary shunting during anaesthesia in man.

Qs/Qt was determined during halothane and oxygen anaesthesia in 22 patients. All were believed to have no pulmonary dysfunction. A surgical operation was in progress and respiration was controlled. Qs/Qt was minimal in 15 of these patients (means 3.9 plus or minus 0.3%), indicating that anaesthesia and operation can be conducted in man without a significant increase of pulmonary shunting. The level of shunting was increased in the other seven patients. In neither group was Qs/Qt altered by the passage of time. Age varied between 23 and 61 years and was directly and significantly correlated to Qs/Qt (r=0.57,P less than0.01).