Increased sympathetic modulation and decreased response of the heart rate variability in controlled asthma.

Objective: To compare the autonomic modulation of heart rate (HR) in asthmatic and healthy volunteers to correlate it with the forced expiratory volume in the first second (FEV1). Methods: Ten healthy and 14 asthmatic volunteers were included in this cross-sectional study. The volunteers underwent a cardiopulmonary exercise test, spirometry and a register of both resting heart rate variability (HRV) in the supine and seated positions along with HRV during the respiratory sinus arrhythmia maneuver (M-RSA). Results: At rest in supine, asthmatic volunteers presented a higher HR (77.1 +/- 9.9 vs. 68.7 +/- 8.7 bpm), shorter interval between two R waves (R-Ri) (807.5 +/- 107.2 vs. 887.5 +/- 112.7 ms) when compared with the healthy volunteers, respectively. Moreover, in the frequency domain of HRV, there was increased low frequency (LF) index (50.4 +/- 17.1 vs. 29.2 +/- 11.1 n.u.) and decreased high frequency (HF) index (49.4 +/- 17.1 vs. 70.7 +/- 11.1 n.u.). During the M-RSA, the asthmatic presented higher HR (82.6 +/- 10.0 vs. 72.4 +/- 7.6 bpm) and lower values of R-Ri (746.4 +/- 92.1 vs. 846.4 +/- 81.4 ms) and approximate entropy (ApEn) (0.7 +/- 0.0 vs. 0.8 +/- 0.1). FEV1 was strongly correlated with the change of the continuous beat-to-beat variability of HR (SD2) index from the seated to the supine position (r = 0.78). Conclusion: Controlled asthma in adults appears to induce an increased sympathetic modulation and attenuated response to the postural changes and the M-RSA. Furthermore, there is a correlation between the airways' obstruction and HRV, especially during postural changes.