ACCURACY OF MINI PEAK FLOW METERS IN INDICATING CHANGES IN LUNG-FUNCTION IN CHILDREN WITH ASTHMA

Objective-To assess whether mini flow meters used to measure peak expi ratory flow can track changes in lung function and indicate clinically important changes. Design-Comparison of measurements with a spiromete r and different brands of mini flow meter; the meters were allocated t o subjects haphazardly. Subjects-12 boys with asthma aged 11 to 17 att ending boarding school. Main outcome measures-Peak expiratory flow mea sured twice daily for three months with a spirometer and at least one of four brands of mini flow meter. Results-The relation between change s in lung function measured with the spirometer and those measured wit h the mini flow meters was generally poor. In all, 26 episodes (range 1-3 in an individual child) of clinically important deterioration in l ung function were detected from the records obtained with the spiromet er. One mini flow meter detected six of 19 episodes, one detected six of 15, one detected six of 18, and one detected three of 21. Conclusio ns-Not only are the absolute values of peak expiratory flow obtained w ith mini flow meters inaccurate but the clinical message may also be i ncorrect. These findings do not imply that home monitoring of peak exp iratory flow has no place in the management of childhood asthma but th at the values obtained should be interpreted cautiously.