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cough,sudden, forceful expiration of air from the lungs caused by an involuntary contraction of the muscles controlling the process of breathing. The cough is a response to some irritating condition such as inflammation or the presence of mucus (sputum) in the respiratory tract, as in infectious disease, or to heavy dust or industrial or tobacco smoke. Coughing may also be a reflex action to factors outside the respiratory tract; diseases that are not respiratory in nature (e.g., congestive heart failure or mitral valve disease) often bring on coughing. If there is mucus or a foreign substance in the respiratory tract, the cough should not be hindered since by this action the offending matter is expelled from the body. If, however, the cough becomes exhausting, sedation is indicated.
a reflex act usually occurring as a result of the irritation of the mucous membrane in the respiratory tract during an inflammatory process caused by pathological products (for example, sputum) or foreign bodies. A cough is one of the principal indications of disease in the respiratory organs (larynx, trachea, bronchi, and lungs). The cough center in the brain can sometimes be stimulated without irritation of the respiratory tracts. This is the so-called nervous cough that occurs in cases of fear and embarrassment. A distinction is made between a dry cough (without the formation and secretion of sputum) and a wet cough (with sputum).
The cough stimulus begins by deep inhalation, followed by a tensing of the bronchial and all the respiratory muscles resulting in forced expulsion. In so doing, the rima glottidis is closed, and intrathoracic pressure rises sharply. With the opening of the rima glottidis, the air bursts forth from the respiratory tract, carrying with it the sputum that has accumulated in the bronchi and pulmonary alveoli, dust particles, and so forth. Thus, a cough can be beneficial in helping to cleanse the respiratory tract. However, a protracted and severe cough that occurs with infections of the pleura, liver, and some other organs is harmful to the organism, since a systematic elevation of the intrathoracic and intrabronchial pressure leads to the gradual formation of pulmonary emphysema and impedes the flow of blood through the veins to the heart. This can lead to cardiopulmonary insufficiency.
Treatment is directed at the affliction that has caused thecough. With a wet cough, particularly if it is difficult to bring upthe sputum, expectorants are used; with a dry, persistent cough, cough suppressants are administered.