 Video-assisted thoracoscopic surgery VATS has become a standard technique for addressing all types of thoracic pathology. Insufflation of carbon dioxide CO2 into the operated chest cavity could increase lung collapse and improve surgical field view. The actual thoracic pressure values may not be identical with the presetting on the insufflator display. This overshoot pressure during VATS may compromise cardiac and pulmonary function. The purpose of this study is to evaluate the effects of intrathoracic pressure overshoot during two-lung ventilation on the hemodynamic and respiratory function and clarify the relative safety of two different techniques of insufflation. 