Defense Mechanism

Scope of Problem

Necessity to Cough

Cough is an important normal protective reflex activity which can become a major sign and symptom of lung disease and a significant clinical problem for a large number of patients.

The normal mechanism occurs with an inhalation of gas above FRC followed by closure of the glottis and an increase in intrapleural pressure to 100 cm H2O. About 0.2 seconds after glottis closure, it reflexively opens with resulting turbulent expiratory flow.

Cough Reflex

The cough reflex has 5 components: 1) cough receptors, 2) afferent nerves, 3) a poorly defined cough center, 4) efferent nerves, 5) effector muscles. Key to cough particularly in pathology is the cough receptors. In summary, cough receptors are throughout all the airways and upper G.I. tract. as well as the pericardium and diaphragm.

Causes of Cough

Acute Cough


Chronic Cough


Mechanism - Voluntary or Psychogenic

Reflex Stimulation

Productive Cough

Nonproductive Cough: Irritative Phenomenon




Diagnostic Features

Physical Examination

Roentgenographic Examination

Laboratory Examination

Pulmonary Function Testing

Fiberoptic Bronchoscopy