There is difference of blood flow between right and left lung, and it is also affected by positional change. The purpose of this study is to compare hemodynamics and arterial blood gas changes between two lungs in thoracoscopic surgery with CO2 insufflation

Fourteen thoracoscopic-surgical patient were randomly selected and divided into two groups; Group I : right lung ventilation, Group II: left lung ventilation. Blood gas analysis, blood pressure and heart rate were measured at three stages in lateral position; stage I: 10minutes after two-lung ventilation, stage II: 10minutes after one-lung ventilation and CO2 insufflation, stage III: 10minutes after two-lung ventilation and CO2 deflation.

In both groups, blood pressure and heart rate were slightly increased at stage II, pH was decreased, PaO2 and PaCO2 were increased at stage II and stage III. But changes of pH and PaCO2 were greater in left lung ventilation. Arterial oxygen saturation and base excess did not change in all stages.

Thoracoscopic surgery with CO2 insufflation did not increase the risk of hypoxemia if FiO2 is 1.0. However blood CO2 retension is higher in left lung ventilation than in right one. So we have to observe PaCO2 more carefully when the left lung is ventilated.