title: Accuracy of spirometric and flow-volume indices obtained by digitizing volume-time tracings.
abstract: We tested the accuracy of a new system for deriving standard spirometric indices, maximal expiratory flow rates, and slope ratios from volume-time tracings. A computer-based technique employing a hand-operated cursor was used to put discrete values of volume and time into a memory array. Spirometric values obtained on 102 subjects using the computer system were compared with the corresponding "hand-read" values. The difference between the 2 measuring techniques were not significant for the FVC, the FEV75, and the FEF25-75; however, the average FEV1 differed by 6.7 ml (SD, 20.3 ml), which was significant. In addition, 10 subjects performed FVC maneuvers through a spirometer and flowmeter connected in series. Flows and slope ratios obtained from the volume-time tracings were compared with those obtained directly from the flowmeter. There was a high degree of correlation between the 2 types of flow measurements (r = 0.989), whereas slope ratios were less well correlated (r = 0.589). Configurational detail such as the presence of "bumps" on slope ratio versus volume plots were recovered with the computer technique. Using this new system, it is possible for 1 operator to process 10 to 12 sets of spirometry tracings per hour.
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005069:Evaluation Studies as Topic; D005540:Forced Expiratory Flow Rates; D005541:Forced Expiratory Volume; D006801:Humans; D008838:Microcomputers; D013147:Spirometry / Q000295:instrumentation / Q000379:methods / Q000592:standards*