Use of impulse oscillometry system in assessment of asthma severity for preschool children.

Objective: The National Asthma Education and Prevention Program/Expert Panel Report (NAEPP/EPR)-3 Guidelines for asthma treatment categorize asthma severity based on impairment and risks and on medications administered. The objective of this study was to determine whether impulse oscillometry system (IOS) measures in preschool children are consistent with asthma severity as defined by NAEPP/EPR-3 Guidelines.

Methods: Asthma severity of the 162 subjects (aged 2-5 years) was classified by impairment and risks for exacerbations requiring oral systemic corticosteroids, by medication usage, and by combination classification (higher severity of impairment and risks or medication usage). An experienced pediatrician determined the appropriate medications for each child and parents completed structured questionnaires regarding day and night symptoms and interference with normal activity over the preceding 4 weeks. All children were tested by IOS.

Results: The mean age was 3.7 ± 0.9 years and 91 (56%) of the total patients were males. When asthma severity was based on (1) impairment and risks and (2) medication usage, asthma was "intermittent" in 17.9% and 11.1% of the total patients, "mild persistent" in 42.0% and 50.6% of total patients, and "moderate-severe persistent" in 40.1% and 38.3% of total patients, respectively. The agreement between severity based on impairment and risks and medication usage was not significant. Xrs(5) z-scores differed between intermittent asthma and mild/moderate-severe persistent asthma, as determined by medication usage and combination classification, but not by impairment and risks. As asthma severity (assessed by medication usage) increased, the duration of asthma increased.

Conclusions: Xrs(5) can be used to discriminate intermittent and persistent asthma in preschool children. Further studies with larger sample sizes are warranted to confirm this finding and to determine the underlying mechanism.