New approaches to assessing the functional status of patients with chronic obstructive pulmonary disease

Abstract

The aim of this study was to study the relationship between heart rate variability (HRV), 6-minute walking test (6-MWT) and ergoreflex to assess the functional status of patients with chronic obstructive pulmonary disease (COPD). Methods. The study included men with COPD (n = 64; mean age 64.98 ± 8.67) and control group volunteers without respiratory disease (n = 41; mean age 61.68 ± 9.21). Spirometry, 6-MWT, HRV analysis before, during, and after the external peripheral vascular occlusion test were performed in all patients and subjects of the control group to evaluate ergoreflex (reflex regulation of the body by means of the reaction of ergoreceptors located in muscles to the accumulation of metabolic products and mechanical muscle stretching). Results. The distance covered during the 6-MWT differed significantly between patients with COPD and those in the control group (p < 0.01). In 22 (34.4%) of the 64 patients with COPD, a decrease in saturation rate (SpO2) of ≥ 4% (p < 0.01) was observed during 6-MWT, while no data for SpO2 reduction at rest were obtained. During evaluation of ergoreflex by HRV changes in patients with COPD the data testifying to its hyperactivity, causing persistent predominance of the sympathetic VNS in patients with COPD, that is reflected in "deterrence" of HRV changes during the external peripheral vascular occlusion test. Correlations between 6-MWT, spirometry and HRV have been found, indicating a high level of adherence to 6-MWT in assessing the functional status of patients with COPD. Conclusion. Differences in results of external peripheral vascular occlusion test in COPD patients and healthy subjects are interpreted by hyperactivation of ergoreflex in COPD patients, which is consistent with the increase of muscle fatigue during 6-MWT. The data of 6-MWT correlate with HRV indices, and when the techniques are applied together, the possibilities of estimating the functional status of patients during the load tests are extended. Evaluation of ergoreflex is recommended for objectification of ideas about functional status of patients with COPD before implementation of basic rehabilitation programs.