Variation in peak expiratory flow in children with asthma.

Twice daily peak expiratory flow measurements were obtained at home from 65 asthmatic children and 34 non-asthmatic controls, and a measure of the daily variation in peak expiratory flow was calculated for each child (mean daily variation). Children aged less than 7.5 years appeared unable to provide reproducable peak expiratory flows, but above that age the mean of the mean daily variations was significantly higher for the asthmatics than the controls. This was true even on days when the asthmatics exhibited no wheeze or took no medication. The significance of the findings is discussed, and it is suggested that calculation of the mean daily variation might assist in the assessment of children presenting with atypical respiratory symptoms.