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].