The relationship between heart rate and VO2 in moderate-to-severe asthmatics

Determinants of exercise capacity in children and adolescents with severe therapy-resistant asthma

OBJECTIVE

To evaluate the exercise capacity of children and adolescents with severe therapy resistant asthma (STRA) aiming to identify its main determinants.

METHODS

Cross-sectional study including individuals aged 6-18 years with a diagnosis of STRA. Clinical (age and gender), anthropometric (weight, height and body mass index) and disease control data were collected. Lung function (spirometry), cardiopulmonary exercise testing (CPET) and exercise-induced bronchoconstriction (EIB) test were performed.

RESULTS

Twenty-four patients aged 11.5 ± 2.6 years were included. The mean forced expiratory volume in one second (FEV₁) was 91.3 ± 9.2%. EIB occurred in 54.2% of patients. In CPET, the peak oxygen uptake (VO_2peak) was 34.1 ± 7.8 mL kg^-1 min^-1. A significant correlation between ventilatory reserve and FEV₁ (r = 0.57; p = 0.003) was found. Similarly, there was a significant correlation between CPET and percent of FEV₁ fall in the EIB test for both V_E/VO₂ (r = 0.47; p = 0.02) and V_E/VCO₂ (r = 0.46; p = 0.02). Patients with FEV₁<80% had lower ventilatory reserve (p = 0.009). In addition, resting heart rate correlated with VO_2peak (r=-0.40; p = 0.04), V_E/VO₂ (r = 0.46; p = 0.02) and V_E/VCO₂ (r = 0.48; p = 0.01).

CONCLUSIONS

Exercise capacity is impaired in approximately 30% of children and adolescents with STRA. The results indicate that different aspects of aerobic fitness are influenced by distinct determinants, including lung function and EIB.