Effects of Positive End-Expiratory Pressure on Biventricular Function During One-Lung Ventilation

After induction of anesthesia, including insertion of TEE probe, change position from supine to lateral position. Measure ABGA and cardiac indices for the baseline value. Apply each PEEP (0, 5, 10 cmH2O) serially at the random order. 6 sequences (0-\>5-\>10, 0-\>10-\>5, 5-\>10-\>0, 5-\>0-\>10, 10-\>5-\>0, 10-\>0-\>5) are equally applied to 6 patients (total 6x6=36 patients) who agreed to this study. Measure ABGA and cardiac indices after 20 min at each step of peep apply(3 times).