Laboratory and clinical evaluation of a portable computerized peak flow meter

A mini-Wright based peak flow meter (VMX Mini-Log), which stores the readings together with the time and date of each measurement, has recently been marketed but has not yet been evaluated. The accuracy, reproducibility, and interdevice variability of this instrument were investigated using a pneumotachograph connected in series as a standard. Flows from 100 to 700 L/min were generated by an explosive decompression chamber. The performance of this instrument was also tested in 20 normal subjects and in 20 patients with airflow obstruction. The accuracy of the instrument was expressed as the percentage of error, and reproducibility and interdevice variability were assessed using the coefficient of variation. In the laboratory evaluation, all devices recorded flow rates that were within +/-10% of the pneumotachograph readings at flows between 200 and 600 L/min. At the extreme flow rates of 100 and 700 L/min, the mean error was higher than 10%. The reproducibility of the VMX was within +/-5% at all the flows tested. The interdevice variability was less than 5% at flow rates between 200 and 700 L/min. When tested on normal subjects with PEF between 400 and 700 L/min, the VMX performed well. In patients with airflow obstruction, four devices had greater than 10% error. The largest error was observed in those patients with PEF below 200 L/min. The VMX Mini-Log peak flow meter is accurate and precise in the flow range between 200 and 600 L/min. Its performance, however, may be affected in subjects with airflow obstruction and PEF below 200 L/min.