Introduction: Patients with chronic obstructive pulmonary disease (COPD) are at an increased risk of cardiovascular comorbidities such as pulmonary hypertension or heart failure. Impaired cardiovascular function often has a significant impact on patients with COPD. Oxygen pulse (O2P) is a surrogate for stroke volume. However, studies regarding O2P, health-related quality of life (HRQL), and exercise capacity in patients with COPD are lacking. We aimed to confirm the association between O2P, HRQL, exercise capacity, severe exacerbation of COPD, and other parameters in exercise testing.
Materials and methods: This study included 79 patients with COPD who underwent lung function testing, a cardiopulmonary exercise test (CPET), Borg Dyspnea Scale evaluation, completion of the St. George's Respiratory Questionnaire, and echocardiography. Cardiovascular comorbidities, COPD-related hospitalizations, and emergency room visits were recorded. We compared these parameters between two groups of patients: those with normal peak O2P and those with impaired peak O2P. The relationships of peak O2P with CPET and lung function were analyzed using simple linear regression.
Results: Patients with normal peak O2P had higher exercise capacity (peak oxygen uptake and work rate), better HRQL, lower dyspnea score, lower COPD-related hospitalizations, and higher circulatory and ventilator parameters than patients with impaired peak O2P. According to a simple linear regression analysis, the anaerobic threshold (AT) and forced expiratory volume in one second (FEV1) showed a significant association with peak O2P, and the Pearson correlation coefficients (Pearson's r) were 0.756 and 0.461, respectively.
Conclusion: Peak O2P has a significant impact on exercise capacity, HRQL, dyspnea, COPD-related hospitalization, and circulatory and ventilatory functions in patients with COPD. The AT and FEV1 have strong and moderate associations with peak O2P, respectively. Therefore, peak O2P is an important indicator of disease severity for patients with COPD.
Keywords: cardiopulmonary exercise test; chronic obstructive pulmonary disease; health-related quality of life; hospitalization; oxygen pulse.
© 2019 Wu et al.