Assessment of within-breath impulse oscillometry parameters in children with asthma.

Abstract

Impulse oscillometry (IOS) measures respiratory resistance and reactance during tidal breaths and is a convenient tool for evaluation of lung function. Respiratory resistance and reactance can be measured separately during inspiration and expiration (inspiratory-expiratory analysis). We investigated the differences in inspiratory-expiratory measurements obtained using IOS between children with and without asthma. We analyzed 819 subjects aged 4-18 years, including asthmatic children (n = 600) and controls (n = 219). Asthma was diagnosed in accordance with the American Thoracic Society/European Respiratory Society guideline. Spirometry and IOS were performed in all subjects. In whole-breath analysis, the asthma group had higher resistance at 5 Hz (R5) and reactance area (AX) and lower reactance at 5 Hz (X5) than the control groups. In inspiratory-expiratory analysis, the asthma group showed increased expiratory R5 and AX and decreased expiratory X5 when compared with the control group. The absolute changes in R5, X5, and AX values between inspiration and expiration were greater in children with asthma than those in controls (0.138 ± 0.195 vs 0.102 ± 0.162, P = 0.014; -0.106 ± 0.200 vs -0.086 ± 0.434, P < 0.001 and 0.460 ± 11.63 vs 0.398 ± 2.88, P = 0.002, respectively). Inspiratory-expiratory IOS analysis differentiated asthmatic children from control subjects, reflecting airway narrowing on expiration in pediatric asthma. The changes in R5, X5, and AX between inspiration and expiration can be a useful index for diagnosis of asthma in children without assessment of the response to a bronchodilator.