Patients with poor lung function usually undergo cardiopulmonary exercise testing (CPET) and those with a predicted postoperative maximal oxygen consumption (VO2 max) of >10 ml/kg/min undergo lung resection surgery and still some complications are observed. We aimed to determine other parameters beyond VO2 able to predict postoperative complications in patients undergoing lung resection surgery.METHODS
This is an observational study with longitudinal follow-up. Patients with forced expiratory volume in 1 second (FEV1) or diffusing capacity for carbon monoxide of <40% underwent CPET and those with VO2 max of >10 ml/kg/min were considered fit for surgery. Patients were followed up prospectively for 12 months and postoperative complications and survival were recorded. Physiological parameters obtained during CPET and pulmonary function tests were analysed.RESULTS
Eighty-three chronic obstructive pulmonary disease (COPD) patients were evaluated for surgery between 2010 and 2015. Twenty-four patients were considered unfit for surgery and received an alternative therapy. Fifty-five patients had a VO2 max of >10 ml/kg/min and underwent lung surgery. Among them, 4% died and 41% developed complications postoperatively. Baseline minute ventilation to carbon dioxide output (VE/VCO2) slope was significantly higher among those who developed postoperative complications or died (P = 0.047). Furthermore, VE/VCO2 slope of >35 (at maximal exercise) was the single parameter most strongly associated with the probability of mortality and postoperative complications (hazard ratio 5.14) with a survival probability of 40% after 1 year of follow-up. In a multivariable model, VO2, VE/VCO2 slope of >35 and work load were independently associated with the probability of having an event.CONCLUSIONS
VO2 is not the unique parameter to consider when CPET is performed to evaluate the postoperative risk of lung cancer surgery in COPD patients. The signs of ventilatory inefficiency such as VE/VCO2 slope predict complications better than VO2 does.