Assessment of airflow limitation, airway inflammation, and symptoms during virus-induced wheezing episodes in 4- to 6-year-old children

Background It is disputed whether recurrent episodes of wheeze in preschool-aged children comprise a distinct asthma phenotype. Objective We sought to prospectively assess airflow limitation and airway inflammation in children 4 to 6 years old with episodic virus-induced wheeze. Methods Ninety-three children 4 to 6 years old with a history of mild, virus-induced episodes of wheeze who were able to perform acceptable fraction of exhaled nitric oxide (F eno ) maneuvers and spirometry (with forced expiratory time ≥0.5 seconds) were followed prospectively. Lung function and F eno values were measured every 6 weeks (baseline) within the first 48 hours of an acute wheezing episode (day 0) and 10 and 30 days later. Symptom scores and peak flow measurement were recorded daily. Results Forty-three children experienced a wheezing episode. At day 0, F eno values were significantly increased, whereas forced expiratory volume at 0.5 seconds (FEV0.5 ) significantly decreased compared with baseline (16 ppb [interquartile range {IQR}, 13-20 ppb] vs 9 ppb IQR, 7-11 ppb] and 0.84 L [IQR, 0.75-0.99 L] vs 0.99 L [IQR, 0.9-1.07 L], respectively; both P