Cardiopulmonary Exercise Testing versus Pulmonary Function Test in The Assessment of Respiratory Impairment in Chronic Obstructive Pulmonary Disease Patients

Introduction: Cardiopulmonary exercise testing (CPET) is a non-invasive method for the determination of disability and comprehensive evaluation of exercise responses involving the cardiovascular, pulmonary and musculoskeletal systems. Material and Methods: To assess exercise performance measured by CPET in different chronic obstructive pulmonary disease (COPD) stages and to compare between pulmonary function test (PFT) and CPET in assessing the degree of respiratory impairment. Sixty patients diagnosed with COPD were enrolled in the study. Modified Medical Research Council scale (mMRC) and COPD assessment test (CAT) to evaluate dyspnea symptom. PFT and CPET were performed. Results: There was a significant decrease in peak VO₂ and anaerobic threshold in patients with stages III, IV (p < 0.001), while COPD stage I, II had significantly higher minute ventilation, tidal volume and oxygen pulse (p < 0.001). 76.67% of patients were similarly classified by CPET and PFT, while 23.33% were found to be less impaired according to CPET when compared to PFT. A significant correlation between both VE/VO2 (r = 0.31, 95% CI 0.19–0.92, p < 0.001) and VE/VCO2 (r = 0.69, 95% CI 0.86–1.08, P < 0.001) with FEV1. Whereas, an inverse correlation were found between both VE/VCO 2 (r = –0.34, 95% CI –0.77 –1.11, p < 0.001) and VE/VO₂ (r = –0.55, 95% CI –0.88 to –0.15, p < 0.001), with the degree of air trapping as estimated by RV/TLC ratio. No significant correlation between neither CAT nor MRC and exercise testing parameters. Conclusion: CPET is an extremely valuable method for the determination of functional capacity and exercise intolerance in COPD rather than PFT. CPET is considered a gold-standard tool for better evaluation of respiratory impairment in COPD.