One-lung anesthesia: percent shunt and arterial oxygen tension during continuous insufflation of oxygen to the nonventilated lung.

Twenty-four male patients scheduled for elective pulmonary resection were studied to determine whether continuous insufflation of oxygen to the nonventilated lung would reduce intrapulmonary shunting (Qs/Qt) and arterial oxygen desaturation. Measurements of physiologic variables were made using pulmonary arterial and peripheral arterial catheters. Blood was sampled for analysis and Qs/Qt and other hemodynamic variables were calculated. Significant differences were observed in Qs/Qt and arterial oxygen tensions (PaO2) between patients insufflated and those in whom oxygen was not insufflated. Patients with oxygen insufflation had significantly lower Qs/Qt and consistently higher PaO2. Statistically significant differences in Qs/Qt became apparent after 15, 30, and 45 minutes of one-lung ventilation compared with values for patients not receiving oxygen insufflation. Six of 12 patients without oxygen insufflation had peak Qs/Qt levels greater than 50%, whereas none of the patients in whom oxygen was insufflated had levels that exceeded this amount. Of 12 patients given oxygen insufflation, one had a PaO2 of less than 100 torr at the point of maximum decrease in arterial oxygen tension, compared with six of 12 patients in whom oxygen was not insufflated. These findings suggest that continuous oxygen insufflation of the nonventilated lung during periods of one-lung ventilation reduces Qs/Qt and minimizes arterial oxygen desaturation.