Effect of spirometer temperature on FEV1 in a longitudinal epidemiologicalstudy

Objectives-To assess the magnitude of error in pulmonary function measureme nts introduced by variation in spirometer temperature under held conditions . in a large scale epidemiological study of school children, the influence was investigated of spirometer temperature on forced expiratory volume in 1 second (FEV1) measured with dry rolling seal volumetric spirometers and co nventional body temperature, pressure, and saturation (BTPS) corrections. Methods-linear regression analyses were performed on data from 995 test-ret est pairs on 851 different children, with 1-110 days between test and retes t, and spirometer temperature differences between -13 degrees C and +9 degr ees C. Results-After adjusting for effects of growth (test-retest intervals) and c ircadian variation (changes in times of testing), differences in standard B TPS corrected FEV1 showed significant (p<0.05) dependence on differences in spirometer temperature between tests (-0.24%\degrees C). Conclusions-When spirometer temperatures vary widely, standard BTPS correct ion does not fully adjust for gas contraction. To improve accuracy of volum e measurements in epidemiological studies, additional correction for variat ion in spirometer temperature should be considered.