title: The effect of physiologic and mechanical aging on the performance of peak flowmeters.
abstract: OBJECTIVE
  To investigate the effects of physiologic and mechanical aging on peak flowmeters.
  
  
  METHODS
  Eight each of MiniWright (MW; Clement Clark; Harlow, UK), Personal-Best (PB; HealthScan Products; Cedar Grove, NJ), Vitalograph (V; Vitalograph Ltd; Buckingham, UK), and Breath-Taker (BT; Medical Development Australia; Melbourne, Australia) peak flowmeters were assessed for accuracy and repeatability before and after aging using a computer-driven syringe to deliver peak flows from 100 to 700 L/min. Four of each type of flowmeter were physiologically aged by normal subjects performing up to six peak flows daily for 1 year. The remaining four of each flowmeter were mechanically aged using an accelerated aging device to deliver 2,000 exponential waveforms 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 throughout. The SD of the difference between readings before and after aging ranged 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) showed that 16 flowmeters--5 BTs, 6 MWs, 4 PBs, and 1 V had no significant change in slope after aging. Mechanical aging caused a consistent underreading in PEF at high flow rates. Physiologic aging showed a more variable pattern both within and between flowmeter types. The MW was the most affected by physiologic aging, producing overestimates of PEF by 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 while mechanical aging may provide a guide to the effects of aging, studies using physiologic aging would be more appropriate.
authors.affiliation: Department of Respiratory Medicine, The Alfred Hospital and Monash University Medical School, Melbourne, Victoria, Australia.
authors.forename: D P
authors.initials: DP
authors.lastname: Johns
authors.forename: E
authors.initials: E
authors.lastname: Side
authors.forename: A H
authors.initials: AH
authors.lastname: Kendrick
authors.forename: T J
authors.initials: TJ
authors.lastname: Williams
authors.forename: E H
authors.initials: EH
authors.lastname: Walters
mesh_terms: D004868:Equipment Failure; D006801:Humans; D010366:Peak Expiratory Flow Rate; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000295:instrumentation*; D013997:Time Factors