An analysis of the distribution of specific tidal volume in children with bronchial asthma.

Abstract

The subject treated here is concerned with a physiological application of a new physico-mathematical concept of the pulmonary system to the study of the abnormal conditions prevailing during the asthmatic attack. In twelve children during the asthmatic attack the pattern of distribution of specific tidal volume was found to differ considerably from that of normal children, in the sense that the maximum amplitude of the distribution function takes place for values of the specific tidal volume several times smaller than those at which the function reaches its maximum value in normal children or in the asthmatic child during the symptom-free periods. The apparent volume of the lung is markedly increased with respect to the functional residual capacity during the asthmatic attack. There is also a considerable increase of the intrapulmonary “obstacles”, here defined, which is out of proportion with the increase in the dimensions of the anatomical structures during the asthmatic attack, indicating the presence of distortional factors, such as secretions inside the bronchial tree, changes in the shape of the structures, etc. There are also significant differences between the distribution of specific tidal volume in the asthmatic attack and in chronic obstructive diseases of the lung. The important notion of “homogeneity” coefficient”, a measureable entity specifically characterizing the functional integrity of the pulmonary system, is introduced here and applied to the study of the acute as well as the chronic obstructive diseases of the lung.