Background: The impulse oscillometry system (IOS) is increasingly used to evaluate lung function, but individual results must be compared with appropriate reference values. We aimed to obtain such reference values in Mexican children and adolescents.
Methods: Healthy subjects were recruited from kindergartens and schools after their parents signed a consent letter. Respiratory system impedances (Zrs), resistances (Rrs), and reactances (Xrs) were measured at 5, 10, 15, and 20 Hz, and the resonant frequency, reactance area, and difference between Rrs5 minus Rrs20 were also calculated.
Results: After exclusion of 4 children who were unable to perform an acceptable IOS recording, the final population comprised 283 children (153 females) 2.7-15.4 y of age. As a group, girls tended to have lower Xrs5 and higher Zrs20 and Rrs20 values. In bivariate analyses, all IOS variables had good correlation with age, height, and weight, and a better straight-line fitting was obtained through data transformation to the log10 (age) or reciprocal (height and weight) values. Comparison of regression lines revealed small differences between males and females, especially in Xrs. Multiple linear regression analysis identified height as the most influential variable in the majority of IOS variables, but age also accounted for a moderate-to-large influence in the regression models in many IOS variables.
Conclusions: In this study, we generated reference equations for each IOS variable in healthy children and adolescents. Although these equations were generated in a Mexican population, they are probably also applicable in other Latin American populations with the same ethnic background.
Keywords: impulse oscillometry; normal values; reference values; respiratory impedance; respiratory reactance; respiratory resistance.
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