In a quasi-experimental design study, the haemodynamic and gas exchange effects of acute permissive hypercapnia and its effect on right ventricle during one-lung ventilation in thoracotomy patients were investigated. The effects of normocapnia and hypercapnia one-lung ventilation in 15 patients undergoing pulmonary resection were compared. Hypercapnia was induced by decreasing tidal volume until PaCO2 increased to 60-70 mm Hg. Cardiac index (from 2.93±0.44 to 3.37±0.54 l min-1 m-2, P value < 0.001), tricuspid annular plane systolic excursion (2.16±0.15 to 2.4±0.17 cm, P value <0.001) and right ventricular myocardial performance index (0.319±0.01 to 0.33±0.0, P value<0.001) increased with hypercapnia. Systemic and pulmonary oxygenation improved. With a reasonable cardiovascular reserve and in particular right ventricular function, permissive hypercapnia as a component of one-lung ventilation management (PaCO2 levels up to 60-70 mm Hg are) is likely to be well tolerated in the short-term and clearly beneficial in terms of lung injury avoidance and attenuation.