Clinical validation of automated spirometry used in surveys of large occupational groups: comparison with conventional water spirometry

An accurate, rugged automated spirometer which provides immediate data is useful both clinically and for screening large groups with various environmental exposures. Because the need for such surveys has been increasing, we compared a computerized mass flow-meter with a conventional water spirometer. The same forced expiration was measured by both instruments in the laboratory and during an occupational survey. Mean values for forced vital capacity (FVC) were 96 cc greater by the automated technique in the laboratory (this equals 2.2% of the value by the conventional method, with a correlation, r, of 0.998) and 97 cc greater in the field (2.3% of the conventional method; r = 0.995). Differences between the two methods in the laboratory and field for forced expiratory volume in one second (FEV 1.0) were +24 cc (0.68%; r = 0.996) and +47 cc (1.6%; r = 0.996) and for forced expiratory flow (FEF)25-75--179cc/sec (4.18%; r = 0.968) and -63 cc/sec (2.1%; r = 0.992), respectively. For FVC and FEV1.0, the differences between paired values were less than or equal to 10% of the value by water spirometry in all instances and less than or equal to 5% in 95.5% and 96% of comparisons, respectively. For FEF 25-75 the differences between paired values were less than or equal to 20% in 97.2% and less than or equal to 10% in 84.7% of comparisons. These findings confirm the validity of the measurements provided by the automated spirometer.