Predicting asthma exacerbation by impulse oscillometry evaluation of small airway function and fractional exhaled nitric oxide in preschool children.

Abstract

To study impulse oscillometry (IOS) indices of peripheral airway function and FeNO as predictors of future loss of asthma control in preschool children. Patients aged 3 to 6 years who were actively being treated for asthma and children without asthma were enrolled in the study. Participants had no change in medication on visit 1 and returned for a follow-up visit within 8 to 12 weeks. At the first visit, nursing assessment, symptom history, IOS analysis, FeNO, and physician evaluation were repeated. Fifty-one (64.6%) subjects had lost asthma control (UC-Group) and 28 (35.4%) subjects had maintained asthma control (C-Group) at their follow-up visit. Thirty-two children without asthma were enrolled in the study as a normal control group (N-Group). R5, R5-20, AX, and Z5 values were all significantly higher in subjects whose symptoms remained uncontrolled compared with those in the controlled asthma group (P < .01) and also significantly higher than those in the normal control group (P < .01). FeNO showed no significant difference between the UC-Group and C-Group (P = .399). Four indices-R5, R5-20, AX, and Z5-had an estimated area under the curve (AUC) of greater than 0.8 and were thus easily able to distinguish the UC-Group from the C-Group. AX had the highest overall AUC (0.884) of the investigated parameters, and the optimal cut-off point of 37.435 cm H2 O/L was able to predict future loss of asthma control in preschool children.