Cardiac Autonomic Modulation of Healthy Individuals and Patients with Chronic Obstructive Pulmonary Disease During Spontaneous and Controlled Breathing

Abstract Background: Lung diseases and different forms of breathing may interfere with cardiac autonomic modulation (CAM). Objective: To compare CAM in individuals with chronic obstructive pulmonary disease (COPD) with healthy individuals during spontaneous breathing (SB) and controlled breathing (CB). Methods: Cross-sectional study involving 30 individuals selected by convenience, divided into COPD group (n = 19) and control group (CG; n = 12). All participants were submitted to heart beat recordings during five minutes at rest (SB) and another five minutes during CB performed at six cycles/min. CAM was made by assessment of the heart rate variability (HRV) through time domain (TD) and frequency domain (FD). Comparisons between groups were performed by Mann Whitney test, and significance level was set at p < 0.05. Results: During SB, HRV TD and FD indices were higher in the controls than in the COPD group, respectively - RR intervals (53.2 ms versus 36.6 ms), RMSSD (42.1 ms versus 26.6 ms) (p < 0.05), total power (28322.8 ms2/Hz versus 2011.6 ms2/Hz), and high-frequency band (800.5 ms(2) versus 330.7 ms2). During CB, the CG also showed higher values for the TD parameters pNN50 (11.7% versus 5.1%), RMSSD (48.3 ms versus 26.7 ms), and SD of RRi (64.9 ms versus 44.7 ms), as well as for the low-frequency component of FD analysis (2848.6 ms2 versus 1197.9 ms2). Conclusion: COPD patients have different CAM when compared with healthy individuals during spontaneous (SB) and controlled breathing (CB).

Lactato sanguíneo, antes e após o teste de caminhada de seis minutos, em portadores de doença pulmonar obstrutiva crônica com diferentes graus de obstrução das vias aéreas / Blood lactate before and after the six-minute walk test in chronic obstructive pulmonary diseasepatients with different degrees of airway obstruction

Objective To assess whether the blood lactate of patients with chronic obstructive pulmonary disease elevates more during the six-minute walk test. Methods This cross-sectional study included 29 individuals divided into three groups: control (n=10), mild chronic obstructive pulmonary disease (n=9), and moderate chronic obstructive pulmonary disease (n=10). Disease degree was classified according to the forced expiratory volume of the first second and Tiffeneau index obtained by recent spirometry. All patients underwent anthropometric and clinical assessment. Blood lactate was measured before and after three minutes of the six-minute walk test. The Kruskal-Wallis test compared the data obtained before and after the six-minute walk test, and Spearman's correlation assessed the influence of some variables on blood lactate. The significance level was p<0.05. Results Although the patients with moderate chronic obstructive pulmonary disease had the worst performance in the six-minute walk test as they walked a smaller distance (403.3m) than the patients with mild chronic bstructive pulmonary disease (424.8m) and the controls (541.8m), they had higher mean blood lactate level (2.57mmol/L) than the patients with mild chronic obstructive pulmonary disease (1.46mmol/L) and the controls (0.9mmol/L). Conclusion Higher obstruction of the airways and its systemic repercussions resulted in significant metabolic limitation in patients with moderate chronic obstructive pulmonary disease, expressed by higher blood lactate level and smaller distance walked in the six-minute walk test.