RESUMO
BACKGROUND: The extent of disease in the nonventilated lung is a major determinant of the amount of blood flow to the nonventilated lung during one lung anesthesia. Collapse of a normal lung may be associated with a higher nonventilated lung blood flow and pulmonary shunt. The aim of this study was to compare the difference of pulmonary shunt and arterial oxygenation between right and left one lung ventilation in patients with normal lung in the supine position. METHODS: 50 patients for bilateral thoracic sympathectomy in the supine position were selected. Patient's data (MAP, HR, PaO2, and shunt) were collected and calculated after left lung ventilation (LLV) with 50% and 100% oxygen (20 minutes interval), and after right lung ventilation (RLV) as same method. Patient,s data were compared between left and right lung ventilation. RESULTS: Under 50% oxygen, PaO2 by LLV (78.0 +/- 12.0 mmHg) was lower than PaO2 by RLV (107.7 +/- 27.9 mmHg) and pulmonary shunt by LLV (28.0 +/- 4.8%) was higher than pulmonary shunt by RLV (22.0 +/- 5.7%). Under 100% oxygen, PaO2 by LLV (143.2 +/- 28.5 mmHg) was lower than PaO2 by RLV (201.1 +/- 3.6 mmHg) and pulmonary shunt by LLV (29.7 +/- 2.5%) was higher than pulmonary shunt by RLV (25.8 +/- 2.7%). CONLUSION: Under 50% oxygen, left lung ventilation in patient with normal lung has higher risk of hypoxemia compared to right lung ventilation during one lung anesthesia in the supine position.