Physiology of Cough

Physiologically, a cough is an attempt by the body to remove secretions or foreign material from the airways. An effective cough, i.e., one that generates a high velocity (remember: velocity is not the same as flow) of gas moving through the airways, is the result of the following sequence of events: Inhalation to a high lung volume Closure of the glottis Contraction of the expiratory muscles with generation of high positive intra-thoracic pressures Opening of the glottis Continued contraction of the expiratory muscles. Thus, individuals with expiratory muscle weakness, vocal cord pathology, or tracheostomies are often unable to clear their airways effectively.