Comparative evaluation of five peak flow devices.
The Wright peak flow meter (WPFM), the pediatric WPFM, the mini-WPFM (MWPFM), the Vitalograph pulmonary monitor (VPM), and prototypes of the newly designed peak flow whistle (PFW) were evaluated and compared under controlled laboratory conditions. With steady flows, all devices compared significantly with the pneumotachygraph standard (p less than 0.001). At transient flows there was distortion of the wave form by the VPM, with significant reduction in the generated peak flow. All devices except the PFW demonstrated progressive increases in resistance with higher flows. The PFW showed a progressive decrease. The WPFM and the pediatric WPFM demonstrated adequate calibration corrections for this increasing resistance. The MWPFM gave slightly higher values than the pneumotachygraph and graph standard. Results with all devices were found to be reproducible after 350 pulses of transient flow of 4 L/sec and no interinstrument variance was detected in the paired devices. Flow values measured at air temperature of 37 degree C tended to be lower than those measured at 28 degree C, but this was not significant at the p less than 0.05 level.