Reduction in cardiorespiratory fitness after lung resection is not related to the number of lung segments removed

AIM: To evaluate the effect of lung cancer surgery on cardiorespiratory fitness (CRF), and to assess the agreement between the predicted postoperative (ppo) V̇O(2peak) and actually measured postoperative peak oxygen uptake (V̇O(2peak)). METHODS: Before and 4–6 weeks after lung cancer surgery, 70 patients (35 women) underwent measurements of pulmonary function and CRF via a cardiopulmonary exercise test. In addition, the 23 non-exercising patients underwent measurements after 6 months. The ppo V̇O(2peak) calculated from the number of functional segments removed was compared with the actually measured postoperative values of V̇O(2peak) for accuracy and precision. RESULTS: After surgery, the V̇O(2peak) decreased from 23.9±5.8 to 19.2±5.5 mL/kg/min (−19.6±15.7%) (p<0.001). The breathing reserve increased by 5% (p=0.001); the oxygen saturation remained unchanged (p=0.30); the oxygen pulse decreased by −1.9 mL/beat (p<0.001); the haemoglobin concentration decreased by 0.7 g/dL (p=0.001). The oxygen pulse was the strongest predictor for change in V̇O(2peak); adjusted linear squared: r(2)=0.77. Six months after surgery, the V̇O(2peak) remained unchanged (−3±15%, p=0.27). The ppo V̇O(2peak) (mL/kg/min) was 18.6±5.4, and the actually measured V̇O(2peak) was 19.2±5.5 (p=0.24). However, the limits of agreement were large (CI −7.4 to 8.2). The segment method miscalculated the ppo V̇O(2peak) by more than ±10 and ±20% in 54% and 25% of the patients, respectively. CONCLUSIONS: The reduction in V̇O(2peak) and lack of improvement 6 months after lung cancer surgery cannot be explained by the loss of functional lung tissue. Predicting postoperative V̇O(2peak) based on the amount of lung tissue removed is not recommendable due to poor precision. TRIAL REGISTRATION NUMBER: NCT01748981.