Reference Equations for Impulse Oscillometry System Parameters in Healthy Brazilian Children and Adolescents

The impulse oscillometry system is a noninvasive method of evaluating respiratory mechanics that is being increasingly used in the pediatric population. To date, no reference equations have been developed for healthy Brazilian children and adolescents. The purpose of the study was to determine the reference equations for impulse oscillometry system parameters in healthy children and adolescents.

We undertook an observational cross-sectional analytical study with healthy students age 6-14 y from educational institutions in the Greater Florianópolis area. Biometric data were evaluated (weight, height, body mass index, and body surface area) as predictors and for sample characterization. All participants were submitted to evaluation of respiratory mechanics using an oscillometry system following American Thoracic Society standards. Three tests were recorded, with data acquisition for ≥20 s. For data normality verification, the Kolmogorov-Smirnov test was applied, and Pearson's correlation test identified the relationship between the predicted values of height, age, and weight and the oscillometric variables of resistance at 5 and 20 Hz reactance; respiratory impedance at 5 Hz resonant frequency; and reactance area. Models were developed using simple linear regression and multiple analyses.

After the recruitment of 864 children, 123 subjects with an average age of 10.0 ± 2.4 y for boys and 9.9 ± 2.4 y for girls (P = .94) were considered for final analysis. Correlations were identified between the dependent and predictor oscillometric variables, with height identified as having the greatest predictive power in the equations developed for boys in all oscillometric parameters, with a mean adjusted R(2) of 46.51%. Age had greater influence on resonant frequency (adjusted R(2) = 40.1%) and reactance area (adjusted R(2) = 48.8%) for girls.

Reference equations were developed for males and females, and height was the most influential predictor variable for most impulse oscillometry system parameters in the population studied.