Background The heart rate (HR) kinetics as well as other predictors of functional capacity such as the Chronic Obstructive Pulmonary Disease (COPD) Assessment Test (CAT), the Duke Activity Status Index (DASI) and the handgrip strength (HGS) represent important tools in assessing the impact of COPD on exercise performance and health status of individuals with COPD. Purpose To verify the relationship between functional capacity, measured using the six-minute walking test (6MWT), with the HR off-kinetics, HGS and the DASI and CAT scores. Methods For this cross-sectional study, 29 subjects with COPD underwent body composition, pulmonary function and cardiac function tests. Subsequently, the DASI and CAT questionnaires and HGS test were performed. The beat-to-beat R-R intervals (IRR) were collected in rest, during the test and in recovery after the 6MWT. The HR off-kinetics was obtained during a 360-second period in post-exercise recovery through the HR mono-exponential decay. Results Moderate correlations were observed between: 1) walked distance (WD) in the 6MWT and the CAT and DASI scores (r= −0.58, p=0.001 and r= 0.58, p=0.001, respectively); 2) WD and HGS (r=0.37, p=0.05); 3) and WD and HR off-kinetics (τ; r= −0.54, p=0.002 and MRT; r= −0.55, p=0.002, respectively). Conclusion The 6MWT performance is a direct measurement to evaluate functional capacity. Additionally, it is related to other direct and indirect markers for functional evaluation in patients with COPD. These results suggest the application of these tools in clinical practice, based on the accessibility, non-invasive character and easy applicability of these methods.

No abstract

Background: Chronic obstructive pulmonary disease (COPD) leads to pulmonary and systemic involvement that could damage the cardiac autonomic modulation (CAM), increasing cardiovascular risks and mortality rates. The obstructive sleep apnea (OSA) syndrome is also associated to harmed CAM. However, it is not clear if the presence of OSA in COPD patients causes an additional loss on the autonomic nervous function. Objective: To compare the responses of CAM during the respiratory sinus arrhythmia maneuver (RSA-M) between patients with OSA and COPD overlapped and COPD on isolation. Materials and Methods: Twenty-four patients (COPD, n = 11; OSA-COPD, n = 13) underwent pulmonary, cardiac function, and home sleep tests for diagnosis and staging of the disease. Heart rate (HR) and R-R intervals were collected during spontaneous breathing (SB) (sitting [10 min]) and the slow and deep breaths to trigger RSA-M (sitting [4 min]). Results: Both groups showed impaired responses when SB and RSA-M were compared. Both COPD and OSA-COPD patients showed increased sympathetic modulation, observed through increased LF (low frequency), and LF/HF ratio (P < 0.05) and decreased HF (high frequency) (P < 0.05), an opposite pattern to that expected for RSA-M. In addition, OSA-COPD showed worse HR variability complexity response on RSA-M (interaction effect, P < 0.05) and reduced spectral peak when contrasted with COPD alone (P < 0.05). Conclusions: The results suggest the presence of both COPD and OSA lead to a negative impact on the autonomic control of HR and deep-breathing exercises. Future clinical trials that investigate the impact of breathing exercises on these autonomic indices should address the relevance of improving the autonomic balance in these patients.