Tracheobronchial Collapse During Couqh

Abstract

CINEBRONCHOGRAPHIC studies in more than 100 adult patients with chronic pulmonary diseases have shown areas with abnormal degrees of airway collapse during cough (Fig. 1) in all cases. The degree of airway collapse was considered abnormal when the cross-sectional area of the lumen was reduced to one-half or less during cough (Fig. 2). Both the location and the degree of airway collapse were found to follow a pattern which varied with the extent of the pulmonary disease. Patients with an early stage of pulmonary disease and a hacking cough for several months or a few years had Type I airway collapse involving the proximal subpleural bronchi which are supported by horseshoe-shaped cartilages and the distal subpleural bronchi which are supported by cartilaginous plates (Fig. 1). These bronchi are the basal bronchi of the lower lobes, the right middle lobe bronchus, the bronchus intermedius, the lingula, and the distal portion of the left main bronchus. In patients with an intermediate stage of the disease, the mediastinal airways consisting of the right main and proximal portions of the left main bronchi and the trachea, all supported by the horseshoeshaped cartilages, were involved in Type II airway collapse during cough. Patients in a late stage of chronic pulmonary disease, which is associated with parenchymal fibrosis and/or emphysema, were seen to have Type III collapse of the intrapulmonary segmental and distal airways during cough. After the glottis opens during the cough cycle, the intrathoracic pressure momentarily remains slightly higher than the intraluminal, and this causes the normal decrease in the caliber of the airways (Figs. 2 and 6). This normal decrease in the cross-sectional area of the airways serves to increase the speed of airflow, thus making the cough more effective. Patients with habitual cough due to chronic pulmonary disease have repeated exercise of their respiratory muscles and can produce abnormally high intrathoracic and intraluminal pressures as the glottis closes during the cough cycle. The time required for equalization of these higher pressures as the glottis opens during cough is likewise increased, and this is responsible for the abnormal degree of tracheobronchial collapse in patients with chronic pulmonary disease. Tracheobronchial collapse during cough produces obstruction to the flow of air, as well as a decrease in the expulsion of pulmonary secretions and exudate. In this way, the severity and peripheral location of the inflammatory reaction become progressively greater during repeated acute respiratory infections. Resolution of subsequent clinical, as well as subclinical, foci of pneumonia is usually followed by parenchymal fibrosis and the development of varying degrees of emphysema. Type I airway collapse during cough, limited only to the proximal and distal subpleural bronchi (Fig. 1), was found to be reversible by satisfactory medical therapy in two patients.