Mechanics of cough in normal subjects and in patients with obstructive respiratory disease.

' 0 Chronic bronchitis is characterized by Illcreased secretions and may be associated with impairment of ciliary function and with airway obstruction. The increased coughing observed in patients with chronic bronchitis reflects their increased dependence on this clearance mechanism and perhaps also its decreased efficiency; several coughs may be needed to do the job that one effective cough might have accomplished. Changes in caliber of the airways during cough have been studied radiologically _by Di Rienzo (1), who suggested that dunng coughing a swift peristaltic wave runs from the small bronchi toward the trachea. Stutz (2) suggested that the changes in caliber _of the airways during cough, measured radiOgraphically, could be explained by !ntrathoracic pressure changes. Ross, Gramiak, and Rahn (3) and Marshall and Holden (4) have compared changes in bronchial diameter during cough with simultaneous measurements of air flow rate and esophageal pressure, and agree that diameter changes can be explained by intrathoracic pressure changes. Several workers have reported physiologic