Relation between tracheal size and forced expiratory volume in one second in young men.

Maximal expiratory flow-volume curves and spirometry were measured in 49 white, nonsmoking, asymptomatic men 19 to 23 yr of age and 179 to 184 cm tall. Because of the uniformity of sex, age, height, and ethnic group, conventional predicted values for these men were virtually identical. Nevertheless, the between-subject coefficient of variation in spirometric and maximal flow results varied from 10% for vital capacity (VC) and forced expiratory volume in one second (FEV1) to 29% for maximal flow when 25% of VC remained to be expired. Confirming previous results, between-subject coefficient of variation was not reduced by expressing flow as VC/s instead of L/s. Eighteen of these men had standard posteroanterior and lateral chest radiographs to measure tracheal diameters at total lung capacity. Both tracheal cross-sectional area and anteroposterior diameter were positively related to FEV1 (r = 0.73, p = 0.001), the relationship being slightly stronger than with peak expiratory flow. There was a trend for VC also to be related to tracheal dimensions. As 50% of residual between-subject variation in FEV1 in these men was accounted for by variation in tracheal size, predicted values of FEV1 in an individual subject might be usefully refined by measuring tracheal size in epidemiologic surveys, thus allowing interpretation of small deviations from mean predicted values. Further studies are required on the variation in tracheal size in a more heterogeneous population.