Autonomic modulations in patients with bronchial asthma based on short-term heart rate variability

Background: Although enhanced cholinergic activity of asthmatics has been established early on, little heart rate variability (HRV) studies were done on asthma patients. Previous HRV studies were based on 24-hour recordings and therefore have not considered the extremely labile activity of bronchial asthma.

Objective: To evaluate the pattern of autonomic modulations in asthmatic patients based on short-term HRV studies.

Materials and methods: The study involved 100 asthmatic patients with an age range of 20-40 years. Asthma activity was evaluated over the last month prior to patients' assessment using asthma control test (ACT). Allflow Spirometer was used for assessing pulmonary function, while Biocom 3000 electrocardiography recorder was used for studying 5-minute HRV. Data was analyzed using the Statistical Package for the Social Sciences Software. Heart rate and asthma medications were introduced as a covariate when studied variables were screened for significant correlation between measurements of asthma severity and heart rate variability indices using partial correlations.

Results: The level of asthma control correlate positively with both normalized low frequency (LF Norm) and the ratio of low frequency/high frequency (LF/HF) (CC = 0.302, 0.212 and P = 0.002, 0.036, respectively) and negatively with HF Norm (CC = -0.317, P = 0.001). Duration of asthma correlates positively with normalized high frequency (HF Norm) (CC = 0.235, P = 0.020) and negatively with LF Norm (CC = -0.250, P = 0.013).

Conclusion: Poor asthma control is associated with lower HRV, depressed sympathetic and enhanced parasympathetic modulations especially in those with longer asthma duration.