Kinetic analyses as a tool to examine physiological exercise responses in a large sample of patients with COPD

Abstract

Kinetic features such as oxygen uptake ((V) over dotO(2)) mean response time (MRT), and gains of (V) over dotO(2), carbon dioxide output ((V) over dotCO(2)), and minute ventilation ((V) over dotE) can describe physiological exercise responses during a constant work rate test of patients with chronic obstructive pulmonary disease (COPD). This study aimed to establish simple guidelines that can identify COP]) patients for whom kinetic analyses arc (un)likely to be reliable and examined whether slow (V) over dotO(2) responses and gains of (V) over dotO(2). (V) over dotCO(2), and (V) over dotE. are associated with ventilatory. cardiovascular, and/or physical impairments. Kinetic features were examined for 265 COPD patients [forced expiratory volume in 1 s (FEV1): 54 +/- 19%predicted] who performed a constant work rate test (duration > 180 s) with breathby-breath measurements of (V) over doto(2), (V) over doto(2). and (V) over dotE. Negative/positive predictive values were used to define cutoff values of relevant clinical variables below/above which kinetic analyses are (un)likely to be reliable. Kinetic feature values were unreliable for 21% (= 56/265) of the patients and for 79% (= 19/24) of the patients with a peak work rate (WRpeak)< 45 W. Kinetic feature values were considered reliable for 94% (= 133/142) of the patients with an FEV1 > 1.3 L. For patients exhibiting reliable kinetic feature values, (V) over dotO(2) MRT was associated with ventilatory (e.g., FEV1 %predicted: P < 0.001: r = -0.35) and physical (e.g.. (V) over dotO(2peak) %predicted: P = 0.009; r = -0.18) impairments. Gains were mainly associated with cardiac function and ventilatory constraints, representing both response efficiency and limitation. Kinetic analyses are likely to be unreliable for patients with a WRpeak < 45 W. Whereas gains enrich analyses of physiological exercise responses, (V) over dotO(2) MRT shows potential to serve as a motivation-independent, physiological indicator of physical performance. NEW & NOTEWORTHY A constant work rate test that is standardly performed during a prerehabilitation assessment is unable to provide reliable kinetic feature values for chronic obstructive pulmonary disease (COPD) patients with a peak work rate below 45 W. For patients suffering from less severe impairments, kinetic analyses are a powerful tool to examine physiological exercise responses. Especially oxygen uptake mean response time can serve as a motivation-independent, physiological indicator of physical performance in patients with COPD.