Lactology Foundation

Cough

Cough, sputum production, and dyspnea are the cardinal features of respiratory diseases. One of these symptoms may prevail according to the underlying pathology, but quite often they occur concurrently. Cough and expectoration are particularly frequent in patients suffering from chronic airway diseases, such as chronic obstructive lung disease, bronchial asthma, bronchiectasis, and, in severe forms, i. e., at a certain level of functional impairment, patients complain about shortness of breath. However, in restrictive lung diseases dyspnea is often the leading complaint, whereas an unproductive cough remains a complementary symptom.

Pathophysiology
Cough is a complex reflex initiated by the irritation of cough receptors located in the upper and lower airways. Cough serves as a protective mechanism against noxious inhalants. It represents an important bronchial clearancemechanism, indicates air pollution, and is a cardinal symptom of various lung diseases. In healthy persons cough is a physiologic reaction to inhaled irritants, in sick people it is the most common and often the first symptom of a diseased lung. Cough may indicate impaired mucociliary clearance, which requires an intact respiratory epithelium and bronchial secretion of normal rheologic properties. Viral infections of the lower airways are the most common causes for transiently impaired mucociliary clearance, whereas cigarette smoking is the most common cause for a permanently damaged clearance.
Clinical Findings
A distinction should be made between acute and chronic, as well as between unproductive, i. e., dry and productive cough, i. e., cough accompanied by sputum production.
Acute episodes of cough are common at any age and are most often due to viral airway infections. In this case, cough is self-limiting and needs no further work up. Treatment is either not necessary or only symptomatic. Chronic cough lasts longer then-eight weeks by definition. It is quite often a diagnostic challenge.
Etiology
The following diseases can cause chronic cough. In children, cough is frequently due to prolonged viral infections or postviral bronchial hyperreactivity. In childhood, cough is quite often the single symptom of asthma. Other causes are: foreign body aspiration, cystic fibrosis, and other lung diseases, which lead to impaired development and growth. In adults, the most common causes of cough are chronic bronchitis in cigarette smokers, bronchial asthma, chronic rhinosinusitis with postnasal drip, and gastroesophageal reflux. Other causes are bronchial carcinoma, tuberculosis, and diffuse infiltrative lung diseases. Chronic coughmay also be due to left-sided heart failure or it is caused by treatment with angiotensin converting enzyme (ACE) inhibitors. In elderly people cough may be due to recurrent aspiration or an aspirated foreign body. Cough is rarely a leading symptom in diseases of the pleura, the diaphragm, or the pericardium. Rare cases have been reported in which cough was due to an irritation of the ear drumby hairs in the external ear channel.

Causes for chronic cough