Prediction of Postoperative Complications: Ventilatory Efficiency and Rest End-tidal Carbon Dioxide

Cardiopulmonary exercise testing parameters including ventilatory efficiency (V_E/VCO₂ slope) are used for risk assessment of lung resection candidates. However, many patients are unable or unwilling to undergo exercise. V_E/VCO₂ slope is closely related to the partial pressure of end-tidal carbon dioxide (P_ETCO₂). We hypothesized P_ETCO₂ at rest predicts postoperative pulmonary complications.

Consecutive lung resection candidates were included in this prospective multicenter study. Postoperative respiratory complications were assessed from the first 30 postoperative days or from the hospital stay. Student t test or Mann-Whitney U test was used for comparison. Multivariate stepwise logistic regression analysis was used to analyze association with the development of postoperative pulmonary complications. The De Long test was used to compare area under the curve (AUC). Data are summarized as median (interquartile range).

Three hundred fifty-three patients were analyzed, of which 59 (17%) developed postoperative pulmonary complications. P_ETCO₂ at rest was significantly lower (27 [24-30] vs 29 [26-32] mm Hg; P < .01) and V_E/VCO₂ slope during exercise significantly higher (35 [30-40] vs 29 [25-33]; P < .01) in patients who developed postoperative pulmonary complications. Both rest P_ETCO₂ with odds ratio 0.90 (95% confidence interval [CI] 0.83-0.97); P = .01 and V_E/VCO₂ slope with odds ratio 1.10 (95% CI 1.05-1.16); P < .01 were independently associated with postoperative pulmonary complications by multivariate stepwise logistic regression analysis. There was no significant difference between AUC of both models (rest P_ETCO₂: AUC = 0.79 (95% CI 0.74-0.85); V_E/VCO₂ slope: AUC = 0.81 (95% CI 0.75-0.86); P = .48).

P_ETCO₂ at rest has similar prognostic utility as V_E/VCO₂ slope, suggesting rest P_ETCO₂ may be used for postoperative pulmonary complications prediction in lung resection candidates.