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 (V̇o2) mean response time (MRT), and gains of V̇o2, carbon dioxide output (V̇co2), and minute ventilation (V̇e) 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 COPD patients for whom kinetic analyses are (un)likely to be reliable and examined whether slow V̇o2 responses and gains of V̇o2, V̇co2, and V̇e 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 breath-by-breath measurements of V̇o2, V̇co2, and V̇e. 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, V̇o2 MRT was associated with ventilatory (e.g., FEV1 %predicted: P < 0.001; r = −0.35) and physical (e.g., V̇o2peak %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, V̇o2 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.

Association between patient-reported outcomes and exercise test outcomes in patients with COPD before and after pulmonary rehabilitation

“…Several laboratory-and field-based exercise tests can be performed to measure exercise performance, which is typically affected in patients with COPD [3,8], due to a downward spiral of dyspnea, disability and physical inactivity [9]. Important aspects from the patient's perspective like health-related quality of life (HRQoL), dyspnea, anxiety, depression, and the level of care dependency, all of which have a direct impact on daily life [10], are measured using PROs.…”

Physiological Changes Differ between Responders and Nonresponders to Pulmonary Rehabilitation in COPD

“…V ̇O2 response kinetics, i.e. V ̇O2 MRT and gain, quantify the fundamental parameters of this V ̇O2 response (10,23) (Supplemental Digital Content 1, http://links.lww.com/MSS/C223). MRT describes the time needed to reach 63% of an anticipated steady state, indicating the speed of the V ̇O2 increase at exercise onset.…”

“…For the calculation of V ̇O2 MRT, Box-Jenkins transfer functions with a first order system model and a second order noise model were fitted to the V ̇O2 time series from 30 s before the WR increase until isotime at 180 s after this step WR increase (10,23). The system model fit was then assessed by the normalised root-mean-squared error value (10).…”

“…For the calculation of V ̇O2 MRT, Box-Jenkins transfer functions with a first order system model and a second order noise model were fitted to the V ̇O2 time series from 30 s before the WR increase until isotime at 180 s after this step WR increase (10,23). The system model fit was then assessed by the normalised root-mean-squared error value (10). V ̇O2 gain was calculated as (V ̇O2,isotime -V ̇O2,unloaded)/∆WR where V ̇O2,unloaded was the mean of the last 30 s of unloaded cycling and ∆WR was the WR increase at t=0 s (Supplemental Digital Content 1, http://links.lww.com/MSS/C223).…”

“…Patients exhibiting unreliable kinetic feature values (i.e. unreliable V ̇O2 MRT or gains of V ̇O2, V ̇CO2 and V ̇E) pre-or post-PR were excluded for subsequent kinetic analyses (Figure 1) (10). Kinetic feature values could not reliably be calculated due to (see (10)):…”