A trial of the comparability of peak expiratory flow meters in schoolchildren.

In many circumstances it may not be possible to measure peak expiratory flow rate on all subjects using the same meter. A small trial was carried out to assess the variability of such meters. Five newly calibrated adult Wright peak expiratory flow meters, which gave comparable readings when rechecked on another rotameter, were compared in a trial on 160 schoolchildren. Each child blew once into each meter, and the design was balanced so that the effect of order of blow was eliminated. Statistically significant differences were found between the meters, although the difference between any pair of meters was less than 5% of the average peak flow rats. Since the meters were chosen because they were very similar it is likely that larger differences would be found in other circumstances. This could be an important source of error in multicentre studies where several meters have to be used.