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


OBJECTIVE
We investigated the differences in inspiratory-expiratory measurements obtained using IOS between children with and without asthma.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
['Sol|In Suk|IS|', 'Kim|Yoon Hee|YH|', 'Kim|SooYeon|S|', 'Kim|Jong Deok|JD|', 'Choi|Sun Ha|SH|', 'Kim|Kyung Won|KW|', 'Sohn|Myung Hyun|MH|0000-0002-2478-487X']
D000293:Adolescent D001249:Asthma D001944:Breath Tests D002648:Child D002675:Child, Preschool D005260:Female D006801:Humans D008297:Male D009991:Oscillometry D012129:Respiratory Function Tests D015656:Respiratory Mechanics
impulse oscillometry asthma within-breath analysis