20 November 2019
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 (O 2P) is a surrogate for stroke volume. However, studies regarding O 2P, health-related quality of life (HRQL), and exercise capacity in patients with COPD are lacking. We aimed to confirm the association between O 2P, HRQL, exercise capacity, severe exacerbation of COPD, and other parameters in exercise testing.
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 O 2P and those with impaired peak O 2P. The relationships of peak O 2P with CPET and lung function were analyzed using simple linear regression.
Patients with normal peak O 2P 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 O 2P. 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 O 2P, and the Pearson correlation coefficients (Pearson’s r) were 0.756 and 0.461, respectively.
Peak O 2P 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 O 2P, respectively. Therefore, peak O 2P is an important indicator of disease severity for patients with COPD.