Role of Cardiopulmonary Exercise Testing in Stable Chronic Obstructive Pulmonary Disease Patients

Objectives: This study aimed to determine the role of Cardiopulmonary Exercise Testing (CPET) in uncovering the mechanisms of exercise intolerance in mild-to-severe stable chronic obstructive pulmonary disease (COPD) patients and to correlate the spirometry, 6-min walk test (6MWT), and COPD assessment test (CAT) scoring with the exercise capacity in stable COPD patients. This study was conducted at tertiary referral medical college hospital in South India. Methodology: This was a prospective and observational study conducted among all eligible subjects with stable COPD attending outpatient clinic at PSG Institute of Medical Sciences and research over 1 year during 2021–2022. All patients with a history suggestive of asthma, patients with clinically evident active pulmonary tuberculosis, ongoing or recent exacerbations of COPD within 2 weeks prior to enrolment in the study, and coexisting condition that are contraindicated or render forced expiratory maneuver difficult to perform were excluded from the study. A thorough history was taken and systemic examination was performed. Patients with spirometry postbronchodilator forced expiratory volume in 1 s (FEV1)/ Forced vital capacity (FVC) <0.70 was allowed for the study in accordance with the GOLD recommendations. Based on postbronchodilator FEV1, patients who met the criteria were categorized as mild, moderate, severe, and extremely severe. For all qualified participants, the CAT questionnaire, 6MWT, and MMRC grades were evaluated. The treadmill procedure was then used to perform CPET in all individuals. Results: Thirty patients enrolled in our study were subjected to CPET using treadmill protocol and the variables and the nine panel plot were analyzed. The variables tested were minute ventilation, maximum oxygen uptake, anaerobic threshold, breathing reserve, VE/VCO 2 , oxygen pulse, and the maximum heart rate. In mild COPD, ventilatory inefficiency was the primary cause, while moderate and severe stages show overlapping cardiovascular, metabolic, and deconditioning factors contributed to dyspnea. VO 2 max was not significantly correlated with spirometry but showed meaningful associations with CAT score, MMRC grade, and 6-min walk distance. In practice, simpler tools can approximate CPET with readily available questionnaires and 6MWT to assess exercise tolerance in stable COPD patients. Conclusion: CPET is helpful in delineating the causes of exercise limitation in mild and moderate COPD patients. In severe COPD, there may be an overlap of various causes of exercise limitation and specific tests are warranted to know the exact cause of exercise limitation. The maximum oxygen uptake correlates well with MMRC dyspnea grade, CAT score, and 6 min walk distance. CPET can be useful in suggesting individually tolerated and tailored pulmonary rehabilitation program in mild and moderate COPD. Overall, CPET remains a valuable objective measure of exercise intolerance in COPD, but the strong correlations with dyspnea scores and 6MWD highlight that validated symptom/field tests can serve as practical alternatives to assess functional limitation, especially in the resource-constrained settings.