2.1. Study design
All procedures performed in this study have been approved by local
ethical committee from Universidade Brasil (registration number
2.939.688).
Twenty-four asthmatic children and twenty-four non-asthmatic children
were recruited and took part in the study, after parents’ agreement and
signature of the term of consent. To be include into the study, children
must had at least ≥ 6 months in clinical treatment and be clinically
stable, that is, at least 2 months without exacerbation. The exclusion
criteria were to be non-obese [(BMI ≤20) evaluated by BMI and
multi-frequential octopolar bioimpedance Bioscan 920 II-S (% Body Fat ≤
20%) Maltron Inc, Essex, England], non-hypertense, non-dyslipidemic,
without cardiovascular diseases, never smokers (even not passive
smokers), previous respiratory diseases (except asthma and bronchitis)
and neurological diseases. The anthropometric characteristics of
children enrolled in the study is presented in Table 1.
2.2. Lung Function and
Mechanics
Spirometry and impulse oscillometry were performed to measure pulmonary
function by using Jaeger Masterscreen pulmonary function instrument
(Masterscreen IOS, Erich Jaeger, Hoechberg, Germany) in strict
accordance with the American Thoracic Society/European Society of
Respiratory Diseases guidelines [10]. The reference values for
spirometry were specific for the Brazilian population. Total respiratory
impedance (Z5Hz), total resistance of respiratory system (R5Hz),
resistance of proximal airways (R20Hz), resistance of distal airways
(R5-R20Hz), and pulmonary reactance (X5Hz), resonance frequency (Fres),
and respiratory impedance (Z5Hz) were recorded by impulse oscillometry
as described previously [11].