Results
Of the 445 asthmatic children initially included, 42 were excluded (9 preschoolers and 2 schoolchildren did not perform properly the IOS, and 41 patients did not sign the consent); therefore, 403 (88.6%) asthmatic were included, the mean age was 8.9 years, 57.1% were males, and 22.6% were preschoolers, 59% schoolchildren, and 18.4% adolescents. The severity of asthma according to GINA was 28.3% mildly persistent, 63.8% moderately persistent, and 7.9% severely persistent, and 32.5% were atopic according to the SPT.
Among the demographic characteristics by age category, the presence of an inversion of the reactance curve and the X5 approx. correction is shown in Table 1. The schoolchildren and adolescents with X5 approx. were older, and schoolchildren with X5 approx. were shorter than those without X5 approx. The prevalence of atopy, asthma severity, and use of controller therapy were similar between children with and without X5 approx. correction, by age category. A total of 264 children (65.5%) presented an inversion of the reactance curve and correction of X5 to X5 approx. Patients that required an X5 correction showed a significant lineal tendency by age category (Figure 2).
The percentage of abnormal values in R5, Fes, AX, and D5-20 was significantly higher among preschoolers and schoolchildren who exhibited an inversion of the reactance curve. However, only abnormal values of D5-20 were found among adolescents with an inversion of the reactance curve (Table 2). The mean of all the IOS parameters was significantly higher in children with X5 approx. for all age categories, while the mean of the spirometry parameter (FEF25-75%) was significantly higher in children with X5 approx. for schoolchildren and adolescents (Table 3).
The correlation of X5 approx. with all the IOS parameters and the FEF25-75% was higher than the correlation of X5. The correlation of X5 approx. with AX and D5-20 was strongly negative in adolescents and with D5-20 in preschoolers. The correlation of X5 approx. was considerably negative with R5 and Fres in adolescents, with R5, AX, and D5-20 in schoolchildren, and with R5 and AX in preschoolers (Table 4).