Physiological Responses to Functional Exercise Test in Patients Referred to Pulmonary Rehabilitation Clinic

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Background and Purpose: Pulmonary rehabilitation (PR) is now considered a fundamental component of the integrated disease management of this population. The six-minute walk test (6MWT) is commonly performed to evaluate functional exercise capacity, and few studies have evaluated differences in physiological responses to 6MWT across the case mix of patients receiving PR. The purpose of this study was to compare the physiological responses to the 6MWT in patients referred to the PR program. Methods: A total of 60 patients referred to the out-patient PR program at Physical Therapy Center (National Taiwan University Hospital) were included. The 6MWT was performed according to the American Thoracic Society Statement (ATS) guidelines. Blood pressure (BP) and perceived dyspnea were measured before and after the 6MWT. Heart rate (HR) and arterial oxygen saturation (SpO_2) were continuously monitored by pulse oximetry throughout the test and during the first minute of recovery. The 6-minute walking distance (6MWD) was measured. Results: The case mix was categorized into bronchiectasis (n = 15), and stage I, II, III, and IV chronic obstructive pulmonary disease (COPD) (stage I to IV, n = 9, 17, 13, and 5 respectively). SpO_2 decreased significantly in all groups during the 6MWT (p ＜ 0.0001), with the most prominent reduction in stage III (9%) and IV (8%) COPD, and remained significantly low in stage II, III, and IV COPD one minute after the 6MWT. The percent of 6MWD predicted was significantly lower in stage III, IV, and bronchiectasis compared to stage I and II COPD (all p ＜ 0.05). Maximal HR achieved during the 6MWT was significantly higher in bronchiectasis and stage IV COPD patients compared to other groups (p = 0.03). Recovery HR in one minute remained significantly higher compare to baseline in all groups. Perceived dyspnea increased significantly in all groups during the 6MWT, and the mean increment was 2.6, 2.3, 3.3, 4.0, and 3.4 for stage I, II, III, IV COPD and bronchiectasis, respectively (p ＜ 0.0001). Conclusion: Except for stage I COPD, all patients referred to PR presented with reduced functional exercise capacity. Exercise desaturation and slow heart rate recovery was noted in all patient referred to PR. Clinical Relevance: This result provides evidence that insufficient functional exercise capacity exists in patients with chronic respiratory disease and PR should be provided to these patients if resources, reimbursement; and healthcare professional are sufficient. In addition, O_2 supplementation and careful monitor HR response is recommended during exercise training.