Overview of Chronic Cough
One survey of internists demonstrated that cough is the third most common reason for an office visit. Cough can be acute or chronic. The most common cause of acute cough is an acute respiratory infection. Chronic cough is defined as a cough persisting for more than 3 weeks.
Physiology of Coughing
Nerves called cough receptors are located near the surface of the upper and lower airways. Various agents, including noxious gases and fumes, foreign bodies, viruses and bacteria, acid, and other irritants, stimulate cough receptors to send signals to the brain. The brain then sends signals back to the lungs and respiratory muscles. In response, there is first a deep inhalation and then a forced exhalation. A closed glottis initially stops the forced exhalation. Closure of the glottis causes pressure to increase in the lungs. When the glottis opens, air rushes out of the lungs under high pressure and with high velocity. The increase in airflow and pressure dislodges particles and expels them from the airways.
Chemicals produced in the body, such as substance P and bradykinin, can also stimulate the cough reflex. Structures close to the airways—the pericardium, esophagus, diaphragm, and stomach—also have cough receptors. The bronchial tubes in the smaller branches and the alveoli do not have cough receptors.
Complications of Chronic Cough
A chronic cough can lead to a significant reduction in one's sense of well-being and quality of life. Complications such as insomnia, hoarseness, headache, dizziness, exacerbations of asthma, urinary incontinence, rupture of nasal, anal, and subconjuctival veins, disruption of surgical wounds, and rib fractures may result. More importantly, a chronic cough may be a signal that a significant health problem exists.