A Portable, Adjustable Forced Vital Capacity Simulator for Routine Spirometer Calibration1

A new, portable calibrating device for verification of spirometer accuracy was tested. The instrument produces a volume-time spirogram similar to an exponential curve. In addition, a micrometer-adjustable orifice is available that produces a variety of timed volumes and flow rates. Four “calibrators” with the same orifice dimensions each produced 10 spirograms. The maximal variation for forced expiratory volume in 0.5 second (FEV0.5) and one second (FEV1), forced vital capacity (FVC), and FEV1/FVC (expressed as a percentage of the mean) was less than ± 1.8 and ± 3.4 %, within and between the instruments, respectively. For forced expiratory flow during the middle half of forced vital capacity (FEF25−75), variation within and between instruments was less than ± 2.3 and ± 5.1 %, respectively. The variation within and between instruments for instantaneous flows at 75, 50, and 25 % of FVC were within ± 6.5 and ± 7.3 %, respectively. The mean values obtained from these calibrators for timed volumes and FEF25−75...