Significance of the deviation of the forced expiratory spirogram from the exponential relation

The forced expiratory curve was divided into individual parts which presented its exponential dependencies. The tau-parameter depicting the speed of exponential process was determined for each part. Variations of this parameter during the course of forced expiration reflected obstructive changes in the bronchopulmonary system of man. The method is highly sensitive to the small airway pathology. It enables the determination of the site of the action of a broncholytic and the differentiation between the obstruction of small and large airways. Moreover, it makes it possible to establish whether the expiratory speed improvement is the result of airways obstruction release or the lung restriction release.