Evaluation of the Agreement between Portable Peak Flow Meters and a Calibrated Pneumotachometer

Abstract

INTRODUCTION: Peak flow meters (PFMs) are commonly used in the hospital and in the home to evaluate the response to bronchodilator therapy. The purpose of this study was to evaluate the agreement between four commercially available PFMs and a calibrated pneumotachometer. MATERIALS & METHODS: Four PFM brands were tested (Pulmo-Graph, Pocket, Assess, and Mini-Wright). Manufacturers supplied four of each brand for evaluation. Each device was evaluated when new and again after 200 uses, at an altitude of 150 m above sea level. Peak flow readings measured by these devices were compared to peak flow readings measured simultaneously using a calibrated pneumotachometer. Peak flows generated by 2 healthy subjects ranged from 80-800 L/min. Statistical analysis consisted of calculations of mean (SD), bias, and ANOVA. RESULTS: A significant difference was observed in the bias among the four peak flow meter brands (p < 0.001). The bias changed after 200 uses for the Assess (p = 0.046) and for the Pulmo-Graph (p < 0.001) but not for the Mini-Wright (p = 0.558) or the Pocket (p = 0.267). A significant difference was also observed in the bias among the four units tested for each brand (p <; 0.()1 in each case). The Assess indicated flows less than did the pneumotachometer at low to medium flows, but was in agreement ±10% of the pneumotachometer at high flows. The Mini-Wright indicated flows greater than the pneumotachometer at low flows, less than the pneumotachometer at high flows, and was in agreement ±HI% of the pneumotachometer at medium flows. The Pulmo-Graph indicated flows less than the pneumotachometer at high flows, and was in agreement ±10% of the pneumotachometer at low to medium flows. The Pocket was in agreement±10% of the pneumotachometer over the entire flow range. CONCLUSION: Because we observed differences in the bias of the PFM brands evaluated, we recommend that when serial measurement of peak flow is used to guide management of reversible airways disease, the same device always be used in a given patient.