CLINICAL VALIDATION OF THE WELCH-ALLYN PNEUMOCHECK(TM) HAND-HELD SPIROMETER

Pulmonary function is predictive of morbidity and mortality. Therefore , in epidemiologic studies, researchers seek to measure pulmonary func tion with portable spirometers feasible for use in clinics or particip ants' homes. The purpose of this study was to validate a hand held spi rometer, the Welch-Allyn Pneumocheck(TM), against standard pulmonary f unction tests. The authors used a convenience sample of 66 subjects. A ll subjects were asked to perform three vital capacity maneuvers with the Welch-Allyn Pneumocheck(TM) and then either a water seal spiromete r or heated pneumotach in a hospital pulmonary function laboratory. Th e mean forced vital capacity (FVC) obtained with the Pneumocheck(TM) w as 3.50 liters (standard deviation (SD) = 1.28) compared with 3.31 lit ers (SD = 1.24) for the pulmonary function laboratory. The correlation between the two measures was 0.98; the mean difference was 0.19 L (95 % confidence interval = 0.12 to 0.26). The mean forced expiratory volu me at one second (FEV(1)) was 2.31 L (SD = 1.07) for the Pneumocheck(T M) compared with 2.32 L (SD = 1.06) for the pulmonary function laborat ory values. The correlation between the two measures was 0.99; the mea n difference was 0.01 L (95% confidence interval = -0.03 to 0.04). Of the 46 subjects originally classified by the Pneumocheck(TM) as having FEV(1)/FVC ratios of less than 0.75, 10 (22%) had ratios greater than or equal to 0.75 after correcting for the FVC difference between meth ods. Therefore, there was an excellent correlation between the Welch-A llyn Pneumocheck(TM) and pulmonary function laboratory values for FVC and FEV(1). Small systematic differences in FVC measures can lead to s ubstantial misclassification rates when evaluating FEV(1)/FVC ratios.