Standard values of the maximal expiratory flow-volume curve normalized by total lung capacity

Standard values for the maximal expiratory flow-volume (MEFV) curve normalized by total lung capacity (TLC) were obtained in one hundred and fifty healthy men. We compared age dependency and the coefficient of variation of parameters of the MEFV curve, obtained at given percentages of the vital capacity and normalized by height to those of parameters obtained at given percentages of TLC and normalized by TLC (V %TLC/TLC). At low lung volumes, every parameter showed a larger age dependency and a larger coefficient of variation than at high lung volumes. V %TLC/TLC showed almost the same age dependency and almost the same coefficient of variation than the other parameters. However, in pulmonary patients, V %TLC/TLC seems to detect obstructive impairment more readily in spite of the changes in lung volume. It is suggested that V %TLC/TLC would be more helpful in screening for airflow limitation in various pulmonary disorders than other parameters.