THE EFFECT OF PHYSIOLOGICAL AND MECHANICAL AGING ON THE PERFORMANCE OF PEAK FLOWMETERS

Purpose: To investigate the effects of physiologic and mechanical agin g on peak flowmeters. Materials and methods: Eight each of MiniWright (MW; Clement Clark; Harlow, UK), PersonalBest (PB; HealthScan Products ; Cedar Grove, NJ), Vitalograph (V; Vitalograph Ltd; Buckingham, UK), and Breath-Taker (BT; Medical Development Australia; Melbourne, Austra lia) peak flowmeters were assessed for accuracy and repeatability befo re and after aging using a computer-driven syringe to deliver peak flo ws from 100 to 700 L/min. Four of each type of flowmeter were physiolo gically aged by normal subjects performing up to six peak flows daily for year. The remaining four of each flowmeter were mechanically aged using an accelerated aging device to deliver 2,000 exponential wavefor ms with a peak flow of 600 L/min over a period of 3 h. Results: The V and BT flowmeters were linear and accurate over the range 100 to 700 L /min, while the PB overread at high flows. The MW was alinear througho ut. The SD of the difference between readings before and after aging r anged from 8.6 to 40.6 L/min (mean, 9.2). Comparing the slopes of the relationship of actual against reference peak expiratory flow (PEF) sh owed that 16 flowmeters-5 BTs, 6 MWs, 4 PBs, and 1 V had no significan t change in dope after aging. Mechanical aging caused a consistent und erreading in PEF at high flow rates. Physiologic aging showed a more v ariable pattern both within and between flowmeter types. The MW was th e most affected by physiologic aging, producing overestimates of PEF b y as much as 100 L/min at 500 L/min. Conclusions: We conclude that the effects of physiologic and mechanical aging are different, and that w hile mechanical aging may provide a guide to the effects of aging, stu dies using physiologic aging would be more appropriate.