| Description |
A computer-controlled air pump, developed to simulate spirometry, was used to inject standard waveforms in order to comprehensively evaluate 53 currently available spirometers. The pump generated spirometry waveforms reproducible to within +30 ml over a 6.0 1 volume range. Evaluation of spirometry systems was conducted in four areas: (1) manuals and reference materials, (2) operation procedures, (3) static testing with a 3.0 1 calibrating syringe, and (4) dynamic testing with a spirometry simulator. Manuals were examined to determine the inclusion of applicable material. Operational assessment evaluated the useability, maintenance requirements, and cost of operation of each spirometer. Static evaluation was performed using a precision 3.0 1 calibrating syringe to determine volume measuring accuracy. Volume measuring ability was tested at slow and fast syringe emptying rates. In addition, volume-based spirometers were tested with two different starting volumes. Dynamic testing involved injecting 24 standard waveforms into the spirometers to determine the ability to measure actual patient procedures. A record was made of the ability of spirometers to measure A record was made of the ability of spirometers to measure FVC (forced vital capacity), FEVl (forced expiratory volume in one second), FEFmax (maximum expiratory, or peak, flow), and FEF25.75% (mean forced expiratory flow during the mid 50% of exhaled volume). Results from dynamic testing were matched against performance requirements of the American Thoracic Society (ATS) published in 1979 and updated in 1986. Using the 1986 requirements, 26 devices (49%) were found that measured three spirometry parameters acceptably (FVC, FEVX, and FEF25.75%), 1 (2%) was conditionally acceptable, 9 (27%) were marginally acceptable, and 18 (34%) failed. The evaluation process disclosed software errors in 15 out of 50 automated systems (30%). Most manufacturers responded promptly and submitted systems with corrected software. The state of current spirometer technology shows overall improvement when compared to earlier systems. The percentage of volume-based devices found to be acceptable improved from 67% to 72%; acceptable flow-based spirometers improved remarkably from 0% to 54%, when application of 1979 ATS performance standards determined acceptability. More stringent 1986 ATS standards showed that 66% of the volume and 33% of the flow devices were acceptable. |
