Influência da força da musculatura respiratória sobre a variabilidade da frequência cardíaca em portadores de DPOC.

Abstract

Chronic obstructive pulmonary disease (COPD) is an inflammatory illness with higher mortality. Present significant systemic manifestations such as structural and functional alterations of the respiratory and peripheral skeletal muscles and cardiac autonomic control. AIM: Evaluate the relationship between respiratory muscle weakness and cardiac autonomic modulation in COPD patients. METHODS: Ten COPD patients were allocated in this cross-sectional study. Cardiac autonomic modulation by heart rate variability (HRV) was obtained beat-by-beat using a Polar S810i HR monitor at rest (sitting position) and during respiratory sinusal arrhythmia maneuver (M-RSA). Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) were obtained by a digital manovacuometer. RESULTS: COPD patients presented respiratory muscle weakness with MIP 72±31cmH2O (63.3±27 % predict) and MEP 110±34cmH2O (91.1±27 % predict). In the frequency domain of HRV, COPD patients presented an increase of Low Frequency (LFnu) index [46,9±23,7 vs 75,8±27,2 p=0,01] and a decrease of High Frequency (HFnu) index [52,8±23,5 vs24,0±27,0(un), p=0,01] during M-RSA respectively. Moreover, we found positive correlations between MIP and HFnu (r= 0.742 p= 0.01) and MEP with HFnu (r= 0.661 p= 0.03) of M-RSA. In a linear regression model, we found that the MIP isolated explain 44% of HFnu during M-RSA (r=0.707 p=0.022). CONCLUSION: COPD patients present respiratory muscle weakness and an altered response in cardiac autonomic control during M-RSA. Additional, inspiratory muscle strength was associated with vagal control in these patients.