Background: This study assessed whether the minute ventilation-to-carbon dioxide output (VE/VCO2) slope, a measure of ventilatory efficiency routinely measured during cardiopulmonary exercise testing (CPET), is an independent predictor of respiratory complications after major lung resections.
Methods: Prospective observational analysis was performed on 225 consecutive candidates after lobectomy (197 patients) or pneumonectomy (28 patients) from 2008 to 2010. Inoperability criteria were peak oxygen consumption (VO2) of less than 10 mL/kg/min in association with predicted postoperative forced expiratory volume in 1 second of less than 30% and diffusion capacity of the lung for carbon monoxide of less than 30%. All patients performed a symptom-limited CPET on cycle ergometer. Respiratory complications (30 days or in-hospital) were prospectively recorded: pneumonia, atelectasis requiring bronchoscopy, respiratory failure on mechanical ventilation exceeding 48 hours, adult respiratory distress syndrome, pulmonary edema, and pulmonary embolism. Univariable and multivariable regression analyses were used to identify independent predictors of respiratory complications.
Results: Cardiopulmonary morbidity and mortality rates were 23% (51 patients) and 2.2% (5 patients). The 25 patients with respiratory complications had a significantly higher VE/VCO2 slope than those without complications (34.8 vs 30.9, p=0.001). Peak VO2 was not associated with respiratory complications. Logistic regression and bootstrap analyses showed that, after adjusting for other baseline and perioperative variables, the strongest predictor of respiratory complications was VE/VCO2 slope (regression coefficient, 0.09; bootstrap frequency, 89%; p=0.004). Patients with a VE/VCO2 slope exceeding 35 had a higher incidence of respiratory complications (22% vs 7.6%, p=0.004) and mortality (7.2% vs. 0.6%, p=0.01).
Conclusions: VE/VCO2 slope is a better predictor of respiratory complications than peak VO2. This inexpensive and operator-independent variable should be considered in the clinical practice to refine operability selection criteria.
Copyright © 2012 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.