An evaluation of the Breath-Taker peak flow meter.

This study was designed to evaluate the Breath-Taker peak flow meter, recently released by the Asthma Foundation of Victoria. The performance characteristics of five Breath-Taker units were compared with those of five Wright and five mini-Wright peak flow meters. The between-unit reproducibility of each type of peak flow meter was measured using an explosive decompression device with a peak flow reproducibility of better than 1%. Each individual meter was used to measure the peak flow delivered by the decompression device three times for each of six flow rates (97-622 L/min). The coefficient of variation (CV) was lowest for the Wright meters (mean CV, 4.8%) and, similarly to the Breath-Taker units (mean CV, 8.4%), this decreased with increasing flow. The CV of the mini-Wright meters, however, increased as flow increased (mean CV, 7.5%). The Breath-Taker meter had less inter-unit variability than the mini-Wright meter at peak flows above 200 L/min. The accuracy of the three meter types was assessed by comparing measurements of peak expiratory flow rate (PEFR) made with each type and also with a computerized pneumotachograph system in 30 subjects with various degrees of irreversible airflow obstruction. Each subject performed at least three reproducible PEFR manoeuvres on the pneumotachograph and on each type of meter, in randomized order. The results showed that in comparison with the pneumotachograph system the Breath-Taker meter underestimated PEFRs by a mean of 27 L/min and the mini-Wright meter overestimated PEFRs by a mean of 45 L/min, whereas the Wright meter was not significantly different. Since the differences between the Breath-Taker meter and the pneumotachograph were independent of flow rate, a scale offset would suffice to "correct" the Breath-Taker readings.