Critical Velocity Determined by a Non-Exhaustive Method in Subjects With COPD

• Published in: Respiratory care 2018-03, Vol.63 (3), p.319-325
• Main Authors: Leite, Marceli Rocha, Uzeloto, Juliana Souza, de Alencar Silva, Bruna Spolador, Freire, Ana Paula Coelho Figueira, de Lima, Fabiano Francisco, Campos, Eduardo Zapaterra, Christofaro, Diego Giulliano Destro, Kalva-Filho, Carlos Augusto, Ramos, Dionei, Ramos, Ercy Mara Cipulo
• Format: Article
• Language: English
• Subjects: Analysis; Chronic obstructive lung disease; Exercise tests; Health care costs; Heart rate; Methods; Physiological aspects
• ISSN: 0020-1324; 1943-3654
• DOI: 10.4187/respcare.05637

Exercise training is an effective and low-cost tool for COPD rehabilitation. Thus, validating a non-exhaustive method to determine a patient's anaerobic threshold would be a very interesting tool in practical settings. We aimed to test the reproducibility of critical velocity values determined in a non-exhaustive manner (CV ) and tolerance for exercise performed at this physiological marker in subjects with COPD. Twelve subjects with COPD were evaluated in this cross-sectional study. The study was divided into 2 phases: Phase A consisted of reproducibility of CV for subjects with COPD, and Phase B determined the tolerance for exercise tests performed at this physiological marker. The proposed protocol for determining CV presented fair reproducibility according to blood lactate concentrations (intraclass correlation coefficient = 0.58). However, we cannot consider that the tests were reproducible due to the wide CI (0.03-0.85). Furthermore, moderate and strong correlations were observed between the CV determined by lactate concentration, by oxygen consumption (V̇ ) (r = 0.66), and by heart rate (r = 0.88). However, a high limit of agreement was observed ±1.45 km/h and ±1.55 km/h, respectively. In the tolerance for exercise test, none of the subjects presented lactate destabilization, whereas 3 tests were interrupted by oxygen saturation decline and 1 test was interrupted by hemodynamic instability. Although most of the subjects presented good tolerance for exercise at CV , fair levels of reproducibility were observed in subjects with COPD, even using lactate. Thus, the use of CV determined through double 3-min efforts should be considered with caution.