THE EFFECT OF AIR FLOW AND ORAL PRESSURE ON THE MECHANICS OF BREATHING IN PATIENTS WITH ASTHMA AND EMPHYSEMA.

Abstract

The purpose of this investigation was to determine the difference in airway functional behavior during expiration in two types of obstructive airway disease: diffuse obstructive pulmonary emphysema and bronchial asthma. That there are differences in airway behavior in these diseases is suggested by pathologic observations indicating that the supporting tissue around the airways of the lungs in the patient with emphysema is reduced (1, 2) and that the walls of the airways become thin and more compliant than normal (3, 4). In contrast, the walls of the airways of the lungs in the patient with asthma are thickened, and the lumen is narrowed by edema and by contraction of bronchial smooth muscle (5). Reported studies suggest that in emphysema the increased expiratory resistance is created, at least in part, by the collapse of the compliant airways during expiration (6, 7). The small bronchioles are probably mainly involved (8), but the larger airways also have been shown to collapse (9, 10). In the present study, a simple technique has been employed to differentiate obstructive airway disease secondary to airway collapse from obstructive airway disease secondary to bronchospasm and edema. The effects of varying expiratory air flow and positive pressure within the airways upon vital capacity were measured in normal subjects and in patients with diffuse obstructive pulmonary emphysema or with bronchial asthma. The concept that suggests that vital capacity will change if airway resistance changes is based on (1) many observations in this laboratory that show an increase in vital ca-