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摘要
Portable peak flow meters: physical characteristics, influence of temperature, altitude, and humidity. O.F. Pedersen, M.R. Miller, T. Sigsgaard, M. Tidley, R.M. Harding. ERS Journals Ltd 1994. ABSTRACT: Little is known about the linearity of portable peak flow meters, or about physical gas factors affecting peak expiratory flow (PEF) readings. We there- fore tested five portable peak flow meters of three types in an altitude chamber (sea level to 5,500 m) and in a climate chamber at sea level (7-37°C) to determine the influence of the physical conditions of the gas on the reading of the meters. The nonlinear response of the variable orifice meters was confirmed and, when this was corrected for, the readings of these meters were found to be significantly reduced by higher altitude and lower temperature. The readings from a turbine type of peak flow meter were not affected by altitude but were reduced at low tem- perature. A mathematical model for the variable orifice meters could correct for both their nonlinear behaviour and the effect of gas density (altitude, temperature and humidity). The model showed that correction is not necessary for the differ- ences in gas conditions between calibration and taking of measurements under nor- mal laboratory conditions. All the meters tested had impedances higher than recommended (0.05 kPa·l-1·s) and this may influence PEF at high flows. The mean uncorrected PEF of six healthy subjects when measured with a Mini Wright peak flow meter at sea level and at 3,000 m fell by 5%, but the mean corrected PEF increased by 12%. This increase in PEF was about 60% of that predicted for fully density-dependent flow and agreed with the findings of other similar studies. We conclude that orifice meters give satisfactory PEF readings at different alti- tudes and temperatures, provided adequate correction is made for their nonlin- earity and the influence of gas density.
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关键词
altitude calibration density dependence of peak expiratory flow impedance peak flow meters temperature
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