Reduced exercise capacity and peak ventilation were significant predictors of early mortality in adults with chronic obstructive pulmonary disease, based on data from 126 individuals.
Cardiopulmonary exercise testing (CPET) is a common assessment for cardiorespiratory disease patients, but its role as a predictor of clinically relevant outcomes in chronic obstructive pulmonary disease (COPD) has not been investigated, and data on changes in exercise capacity over time in COPD patients are limited, wrote Cassia da Luz Goulart, MD, of the Federal University of São Carlos, Brazil, and colleagues.
The researchers hypothesized that CPET threshold values could be used as predictors of mortality in COPD.
In a prospective study published in Respiratory Medicine, the researchers identified 126 adults with COPD who were followed for 42 months. At study entry, each patient completed a clinical evaluation, followed by a pulmonary function test and CPET. The average age of the patients was 65 years, and 73% were men. All patients were on optimal medical management for COPD.
The researchers recorded data on peak oxygen consumption (VO2, mL/min), VCO2 (mL/min), minute ventilation (VE, L/min), the oxygen uptake efficiency slope (OUES), and ventilatory efficiency (the VE/VCO2 slope).
The participants performed CPET on a cycle ergometer, with breath-by-breath analysis measured throughout the test using a computer-based system.
A total of 48 patients (38%) died during the 42-month follow-up period. Overall, the significant predictors of mortality were VE/VCO2 slope of 30 or higher, peak VE of 25.7 L/min, and peak VO2 ≤ 13.8 mLO2 kg–1 min–1 were strong predictors of mortality in COPD patients in a Cox regression analysis.
When comparing the 78 survivors to the 48 nonsurvivors, the researchers found that the nonsurvivors were significantly more likely to be women, with worse lung function, inspiratory muscle weakness, and poorer CPET responses (P < .050 for all).
“The VE peak response is directly related to the FEV1 in COPD patients, factors such as dyspnea and increased leg discomfort negatively impact the VE response during exercise,” the researchers wrote in their discussion of the findings. In this context, our results may hold clinical utility in refining the prognostic accuracy when a patient with COPD has a VE peak ≤ 25.7 L/min,” they explained.
The study findings were limited by the inability to assess complete pulmonary function in the COPD patients, and the assessment only of three CPET measures, the researchers noted.
However, the results support the use of CPET as a clinical assessment tool for COPD patients, they said. “Moreover, therapeutic approaches, such as cardiopulmonary rehabilitation, may consider focusing on improving these metabolic and ventilatory markers as an indicator of clinical improvement and prognosis in patients with COPD,” they added.
The study was supported by the Fundação de Amparo a Pesquisa do Estado de São Paulo, Brazil, and by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil. The researchers had no financial conflicts to disclose.