Increased minute ventilation-to-carbon dioxide slope during cardiopulmonary exercise test is associated with poor postoperative outcome following lung cancer resection

OBJECTIVES: Ventilatory efficiency [minute ventilation-to-carbon dioxide output slope (VE/VCO2 slope)] can be measured at sub-maximal workload during cardiopulmonary exercise test. The aim of this study is to assess the association between VE/VCO2 slope and outcome after lung cancer resections. METHODS: Retrospective, single-centre analysis on all patients undergoing lung resection for cancer (April 2014-August 2022) and with a preoperative cardiopulmonary exercise test. VE/VCO2 slope >40 was chosen as high-risk threshold. Logistic regression analysis was used to test the association of VE/VCO2 slope and several patient- and surgery-related factors with 90-day mortality. RESULTS: A total of 552 patients were included (374 lobectomies, 81 segmentectomies, 55 pneumonectomies and 42 wedge resections). Seventy-four percent were minimally invasive procedures. Cardiopulmonary morbidity was 32%, in-hospital/30-day mortality 6.9% and 90-day mortality 8.9%. A total of 137 patients (25%) had a slope of >40. These patients were older (72 vs 70 years, P = 0.012), had more frequently coronary artery disease (17% vs 10%, P = 0.028), lower carbon monoxide lung diffusion capacity (57% vs 68%, P < 0.001), lower body mass index (25.4 vs 27.0 kg/m2, P = 0.001) and lower peak VO2 (14.9 vs 17.0 ml/kg/min, P < 0.001) than those with a lower slope. The cardiopulmonary morbidity among patients with a slope of >40 was 40% vs 29% in those with lower slope (P = 0.019). Ninety-day mortality was 15% vs 6.7% (P = 0.002). The 90-day mortality of elderly patients with slope >40 was 21% vs 7.8% (P = 0.001). After adjusting for peak VO2 value, extent of operation and other patient-related variables in a logistic regression analysis, VE/VCO2 slope retained a significant association with 90-day mortality. CONCLUSIONS: VE/VCO2 slope was strongly associated with morbidity and mortality following lung resection and should be included in the functional algorithm to assess fitness for surgery.