Inspiratory airflow limitation after exercise challenge in cold air in asthmatic children

SummaryMethacholine and histamine can lead to inspiratory flow limitation in asthmatic children and adults. This has not been analyzed after indirect airway stimuli, such as exercise. The aim of the study was to analyze airflow limitation after exercise in cold, dry air.72 asthmatic children with mild to moderate asthma (mean age 13.2 ± 2.2 yrs) performed a treadmill exercise challenge. A fall of >10% in FEV1 was the threshold for expiratory flow limitation and a fall of >25% of MIF50 was the threshold for inspiratory flow limitation. The occurrence of wheeze, stridor and cough were quantified before and after exercise.After exercise, the mean fall in FEV1 was 17.7 ± 14.6%, while the mean fall in MIF50 was 25.4 ± 15.8%; no correlation was found between fall in FEV1 and MIF50 (R2: 0.04; p = 0.717). 53 of the 72 children showed an inspiratory and/or expiratory airflow limitation. 38% (20/53) of these children showed an isolated expiratory flow limitation, 45% (24/53) showed both expiratory and inspiratory flow limitation and 17% (9/53) showed an isolated inspiratory flow limitation. The fall in FEV1 peaked 9 min after exercise and correlated to expiratory wheeze. The fall in MIF50 peaked 15 min after exercise and correlated to inspiratory stridor. The time difference in peak fall between FEV1 and MIF50 was statistically significant (5.9 min; p < 0.001, 99% CI: 2.3–9.5 min).In conclusion, this study shows that an exercise challenge in asthmatic children can give rise to inspiratory airflow limitation, which may give rise to asthma like symptoms