Clinical comparison of two electronic spirometers with a water-sealed spirometer

Two electronic spirometers which use a hot-wire anemometer to measure air flow were clinically compared with a water-sealed spirometer. The forced vital capacity (FVC), the forced expiratory volume in one second (FEV1), the FEV1/FVC%, the mean forced expiratory flow between 200 and 1,200 ml of the FVC, the mean forced expiratory flow during the middle half of the FVC, the mean forced expiratory flow between 75 and 85 percent of the FVC, and the maximum voluntary ventilation were determined for a group of 67 subjects. Techniques are described for connecting the spirometers in series to permit evaluation by human subjects or by syringe injection. High correlation coefficients generally were obtained when comparing the electronic spirometers with the water-sealed spirometer, but the actual range of percent difference was greater than 11 percent in all spirometric tests. The results indicate the need for systematic evaluation of electronic spirometers to characterize their deviation from accented standards. Frequent calibration is necessary to maintain consistent performance.