Analysis of autonomic modulation during maximal and submaximal work rate and functional capacity in asthmatic children.

ABSTRACT

BACKGROUND: Children with asthma experience changes in functional capacity and autonomic control. The literature suggests that this imbalance is responsible for bronchial hyperresponsiveness, primarily during physical effort. OBJECTIVE: The aim of the present study was to evaluate variables of autonomic modulation and functional capacity in asthmatic children after maximum and submaximum work rate. METHODS: A cross-sectional study was carried out with 24 children [18 in the asthma group (AG) and 6 in the control group (CG)]. Evaluations involved heart rate variability (HRV) and functional capacity [shuttle walk test (SWT) and three-minute step test]. Pulmonary function was also evaluated through spirometry and the fractional concentration of expired nitric oxide (FeNO). RESULTS: The asthma diagnostic variables FEV(1) and FeNO differed significantly between groups (p = .01). Distance traveled on the SWT was lower in the AG (333.13 ± 97.25 m vs. 442.66 ± 127.21 m; p = .04). Perceived exertion was greater in the AG. The HRV variables rMSSD and HF did not decrease significantly during the SWT (maximum work rate) in the AG (p = .01 and .04). FeNO was negatively correlated with FEV(1)/FVC (r = -0.70; p = .004) and positively correlated with pNN50 (r = 0.50; p = .03) in the AG. CONCLUSION: From the autonomic standpoint, asthmatic and non-asthmatic children respond differently to stress. No withdrawal of parasympathetic cardiac modulation occurs in asthmatic children after maximum work rate. Children with asthma experience changes in functional capacity and lung function may vary depending on the degree of inflammation of the airways.