Effects of hypercarbia on arterial oxygenation during one-lung ventilation: prospective randomized crossover study

BACKGROUND: This study aimed to evaluate the effects of hypercarbia on arterial oxygenation during one-lung ventilation (OLV). METHODS: Fifty adult patients undergoing elective video-assisted thoracoscopic lobectomy or pneumonectomy were enrolled. Group I patients (n = 25) were first maintained at normocarbia (PaCO(2): 38–42 mmHg) for 30 min and then at hypercarbia (45–50 mmHg). In Group II patients (n = 25), PaCO(2) was maintained in the reverse order. Arterial oxygen partial pressure (PaO(2)), respiratory variables, hemodynamic variables, and hemoglobin concentration were compared during normocarbia and hypercarbia. Arterial O(2) content and O(2) delivery were calculated. RESULTS: PaO(2) values during normocarbia and hypercarbia were 66.5 ± 10.6 and 79.7 ± 17.3 mmHg, respectively (mean difference: 13.2 mmHg, 95% CI for difference of means: 17.0 to 9.3, P < 0.001). SaO(2) values during normocarbia and hypercarbia were 92.5 ± 4.8% and 94.3 ± 3.1% (P = 0.009), respectively. Static compliance of the lung (33.0 ± 5.4 vs. 30.4 ± 5.3 ml/cmH(2)O, P < 0.001), arterial O(2) content (15.4 ± 1.4 vs. 14.9 ± 1.5 ml/dl, P < 0.001) and O(2) delivery (69.9 ± 18.4 vs. 65.1 ± 18.1 ml/min, P < 0.001) were significantly higher during hypercarbia than during normocarbia. CONCLUSIONS: Hypercarbia increases PaO(2) and O(2) carrying capacity and improves pulmonary mechanics during OLV, suggesting that it may help manage oxygenation during OLV. Therefore, permissive hypercarbia may be a simple and valuable modality to manage arterial oxygenation during OLV.