Background. Whether small airway dysfunction (SAD), which is prevalent in asthma, helps to characterize wheezing phenotypes is undetermined. The objective was to assess whether SAD parameters obtained from impedance measurement and asthma probability are linked. Methods. One hundred and thirty-nine preschool children (mean age 4.7 years, 68% boys) suffering from recurrent wheeze underwent impulse oscillometry that allowed calculating peripheral resistance and compliance of the respiratory system (markers of SAD) using the extended RIC model (central and peripheral Resistance, Inertance and peripheral Compliance of the respiratory system). Children were classified using the probability-based approach of GINA guidelines (few, some, most having asthma). A principal component analysis (PCA) that determined the dimensions of wheezing disease evaluated the links between SAD and asthma probability. Results. Forty-seven children belonged to the few, 28 to the some and 64 to the most having asthma groups. Whereas their anthropometrics and measured parameters were similar, the most having asthma group exhibited the lowest mean value of airway inertance after bronchodilator probably due to airway inhomogeneities. PCA characterized nine independent dimensions including a peripheral resistance (constituted by baseline peripheral resistance, AX, R5-20Hz, X5Hz), a central resistance (baseline central resistance, R20Hz) and an airway size dimension (post-bronchodilator inertance and central resistance). PCA showed that the SAD markers were independent from clinical dimensions (control and asthma probability were two other dimensions) and did not help to define wheezing phenotypes. Conclusions. Lung function parameters obtained from impulse oscillometry and asthma probability were belonging to independent dimensions of the wheezing disease.
Background: The Childhood Asthma Management Program study revealed that 25.7% of children with mild to moderate asthma exhibit a loss of lung function. The objective was to assess the trajectories of function by means of serial FEV1 in asthmatic children participating in out-of-hospital follow-up. Methods: A total of 295 children (199 boys) who had undergone at least 10 spirometry tests from the age of 8 were selected from a single-center open cohort. The annualized rate of change (slope) for prebronchodilator FEV1 (percent predicted) was estimated for each participant and three patterns were defined: significantly positive slope, significantly negative slope, and null slope (non-significant P-value in the Pearson test). The standard deviation (SD) of each individual slope was recorded as a variability criterion of FEV1. Results: The median (25th and 75th percentile) age at inclusion and the last visit was 8.5 (8.2, 9.3) and 15.4 (14.8, 16.0) years, respectively. Tracking of function (null slope) was observed in 68.8% of the children, while 27.8% showed a loss of function (negative slope) and 3.4% showed a gain in function (positive slope). The children characterized by loss of function depicted a better initial function and a lower FEV1 variability during their follow-up than children with tracking or gain of lung function. At the last visit, these children were characterized by a lower lung function than children with tracking or gain of lung function. Conclusion: Children with a better initial FEV1 value and less FEV1 variability are more prone to loss of lung function.