Expiratory and inspiratory forced vital capacity and one-second forced volume in asymptomatic never-smokers in Norway

The objectives of this simd, were to examine within and between individual variation detected during forced expiratory, (FE) and forced inspiratory (F I) manoeuvers in a general population and to investigate the dependence of these variables on age, body size, and gender. A random sample of asymptoma tic never smokers who had never been exposed occupationally to quartz or as bestos and who were living on the south-western coast of Norway were examin ed by spirometry; 81% of the individuals invited to attend did so. Of the 4 88 subjects between 18 and 73 years of age, 98% contributed three acceptabl e recordings for forced expiratory vital capacity (FVC) and one-second forc ed expiratory volume (FEV1) 94% contributed three acceptable recordings for forced inspiratory vital capacity (FIVC) and 85% contributed three accepta ble recordings for one-second forced inspiratory volume (FIV1). The within- subject variation increased wit bod height and was considerably larger for FIV1 than for FVC, FEV1 or FIVC. A four- parameter model of pulmonary funct ion measurement divided by height squared, including a gender term and a li near and quadratic term of age, fit the median of the observed values well. The residuals had a close-to-normal distribution, and the fifth-percentile values were estimated as the lower limit of normal. The peak value of dyna mic lung volumes was observed into the middle of the fourth decade of life, and the decline thereafter did not differ greatly between the genders or a mong the different indices. The forced inspiratory volumes are the first re ported in any reference population.