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.