Mechanisms of ventilatory limitation to maximum exercise in children and
adolescents with chronic respiratory diseases
Abstract
Introduction. Exercise intolerance is common in chronic
respiratory diseases (CRD), but its mechanisms are still poorly
understood. The aim of this study was to evaluate exercise capacity and
its association with lung function, ventilatory limitation, and
ventilatory efficiency in children and adolescents with cystic fibrosis
(CF) and asthma when compared to healthy controls. Methods.
Cross‐sectional study including patients with mild‐to‐moderate asthma,
CF and healthy children and adolescents. Anthropometric data, lung
function (spirometry) and exercise capacity (cardiopulmonary exercise
testing) were evaluated. Primary outcomes were peak oxygen consumption
(VO 2peak), forced expiratory volume in 1 second (FEV
1), breathing reserve (BR), ventilatory equivalent for
oxygen consumption (V E/VO 2) and for
carbon dioxide production (V E/VCO 2),
both at the ventilatory threshold (VT 1) and peak
exercise. Results. Mean age of 147 patients included was
11.8±3.0 years. There were differences between asthmatics and CF
children when compared to their healthy peers for anthropometric and
lung function measurements. Asthmatics showed lower VO
2peak when compared to both healthy and CF subjects,
although no differences were found between healthy and CF patients. A
lower BR was found when CF patients were compared to both healthy and
asthmatic. Both CF and asthmatic patients presented higher values for V
E/VO 2 and V E/VCO
2 at VT 1 when compared to healthy
individuals. For both V E/VO 2 and V
E/VCO 2 at peak exercise CF patients
presented higher values when compared to their healthy peers.
Conclusion. Patients with CF achieved good exercise capacity
despite low ventilatory efficiency, low BR, and reduced lung function.
However, asthmatics reported reduced cardiorespiratory capacity and
normal ventilatory efficiency at peak exercise. These results
demonstrate differences in the mechanisms of ventilatory limitation to
maximum exercise testing in children and adolescents with CRD.