[Cardiac autonomic responses to exercise testing in patients with chronic obstructive pulmonary disease]

Incremental exercise testing is used to evaluate exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). The purpose of this cross-sectional, observational study was to compare cardiac autonomic responses of patients to exercise testing with healthy subjects and to investigate their determinants.

Twenty-five COPD patients and 20 healthy subjects participated in the study. Pulmonary function test, arterial blood gas analysis and exercise test were performed. Heart rate, blood pressure and dyspnea were measured before and after the test. Peak oxygen uptake, chronotropic index and heart rate recovery were recorded. Dyspnea perception during daily activities was measured using the modified Medical Research Council dyspnea scale. Student t test, Mann Whitney u test, Spearman correlation coefficients and multiple linear regression analysis were used for statistical analysis.

Peak heart rate, chronotropic index and peak oxygen uptake were significantly lower and exercise dyspnea perception was significantly higher in COPD patients than those of healthy subjects (p<0.05). Forty-eight percent of patients had chronotropic incompetence. Body weight and body mass index of these patients were significantly higher than in those with normal chronotropic response (p<0.05). Baseline, peak and recovery heart rate were significantly lower in patients with chronotropic incompetence (p<0.05). Modified Medical Research Council dyspnea score explained 44% of the variance in chronotropic index (r=0.66; r2=0.44, F (1, 16) =12.46, p=0.003).

Chronic obstructive pulmonary disease patients had chronotropic incompetence to maximal volitional exercise. Dyspnea perception during daily activities is an important determinant of chronotropic incompetence. Effects of desensitization of dyspnea on sympathetic system activation in COPD should be investigated.