Effect of permissive hypercarbia on lung oxygenation during one-lung ventilation and postoperative pulmonary complications in patients undergoing thoracic surgery

BACKGROUND The effect of hypercarbia on lung oxygenation during thoracic surgery remains unclear. OBJECTIVE To investigate the effect of hypercarbia on lung oxygenation during one-lung ventilation in patients undergoing thoracic surgery and evaluate the incidence of postoperative pulmonary complications. DESIGN Prospective randomised controlled trial. SETTING A tertiary university hospital in the Republic of Korea from November 2019 to December 2020. PATIENTS Two hundred and ninety-seven patients with American Society of Anaesthesiologists physical status II to III, scheduled to undergo elective lung resection surgery. INTERVENTION Patients were randomly assigned to Group 40, 50, or 60. An autoflow ventilation mode with a lung protective ventilation strategy was applied to all patients. Respiratory rate was adjusted to maintain a partial pressure of arterial carbon dioxide of 40 ± 5 mmHg in Group 40, 50 ± 5 mmHg in Group 50 and 60 ± 5 mmHg in Group 60 during one-lung ventilation and at the end of surgery. MAIN OUTCOME MEASURES The primary outcome was the arterial oxygen partial pressure/fractional inspired oxygen ratio after 60 min of one-lung ventilation. RESULTS Data from 262 patients were analysed. The partial pressure/fractional inspired oxygen ratio was significantly higher in Group 50 and Group 60 than in Group 40 (269.4 vs. 262.9 vs. 214.4; P < 0.001) but was not significantly different between Group 50 and Group 60. The incidence of postoperative pulmonary complications was comparable among the three groups. CONCLUSION Permissive hypercarbia improved lung oxygenation during one-lung ventilation without increasing the risk of postoperative pulmonary complications or the length of hospital stay. TRIAL REGISTRATION NCT 04175379.