FREQUENCY-RESPONSE OF PORTABLE PEF METERS

Peak expiratory Row (PEF) is a dynamic parameter and therefore require s a measuring device with a high-frequency response. This study evalua ted the frequency-response characteristics of eight commercially avail able PEF meters, using simulated forced-expiratory maneuvers with a co mputer-controlled mechanical pump. Three different PEF levels were use d (200, 400, and 600 L/min) at six levels of harmonic-frequency conten t similar to those observed in human subjects. For waveforms with high er frequency content (at the high end or above the physiologic range), the Assess, Vitalograph, Pocket Peak, and Spir-O-Flow PEF meters all overread PEF (greater than 15% difference from target values) at all t hree PEF levels. These results suggest that the frequency response of PEF meters is an important consideration in the selection of such mete rs and should be included in device requirements. The current practice of using various levels of American Thoracic Society (ATS) waveform 2 4 with its low-frequency content may not adequately evaluate the frequ ency characteristics of PEF meters. An upper range (5% of the fundamen tal frequency) of 12 Hz, within the range observed in normal subjects, appears to be more practical than an upper limit of 20 Hz.