Cough

COUGH (tussis), a reflex act by which substances accumulated in the respiratory apparatus are expelled (normal secretions of the bronchial mucous membrane, products of exudation and transudation, extravasated blood, and products of decomposition of diseased tissues). By means of the cough reflex, the organism also attempts to rid itself of foreign bodies that have accidentally entered the larynx, trachea, or bronchi. The mechanism of cough is as follows. After a deep inspiration follows a spasmodic forced expiration with the glottis initially closed, then the glottis quickly opens, and the air in the trachea and lungs under high pressure forcefully escapes outward. At the moment of coughing, the soft palate covers the nasopharyngeal cavity, and the strong stream of air passing through the mouth carries with it everything that is in the larynx, windpipe, and large bronchi. The center regulating this entire complex act lies in the medulla oblongata near the respiratory center. The cough center is often excited by reflex from various areas of the mucous membrane of the respiratory tract due to irritation of the sensory endings of the n. vagus and much less frequently by irritation of the sensory endings in other organs.--C. becomes difficult when there is destruction or paralysis of the vocal cords and becomes impossible in exhausted persons with diminished function of the respiratory muscles. Diminished sensitivity of the endings of the branches of the n. vagus in the bronchial mucous membrane also leads to a decrease in the cough reflex. For example, in bronchiectasis, patients develop C. only when changing body position, i.e., when accumulated secretions from the bronchiectatic cavity with destroyed mucous membrane move onto fresh, non-desensitized mucous membrane of the draining bronchus. Diminished threshold of irritation of the endings of the branches of the n. vagus explains the disappearance of C. in patients in an unconscious state (brain diseases, typhus).--Experiments on animals and clinical observations have shown a number of particularly sensitive spots, irritation of which can easily produce the cough reflex. Such sensitive points are the regio interarytaenoidea in the larynx (n. laryngeus superior), the posterior wall of the trachea and the bifurcation (n. vagus). Sometimes true paroxysms of C. are observed with external contact with the skin, with pressure on the mammary glands, ovaries, during probing of the cervix. Cases of C. have been described in diseases of the peritoneum, stomach diseases, during palpation of the liver and spleen. Kolits succeeded experimentally in producing C. from the medulla oblongata. Apparently of the same origin is C. in the clinical picture of laryngeal crises. The origin of cortical C. is also possible under other conditions (e.g., habitual C. with normal mucous membrane of the pharynx and bronchi). To this same group of cortical C. should be included C. appearing under the influence of emotional excitement, fear, embarrassment. From cortical centers, suppression of C. can also arise, i.e., C. can be suppressed to a certain extent. True, if the irritation sent from the periphery, e.g., from the bronchial mucous membrane, reaches a certain limit, then suppression of C. becomes difficult and even impossible. The possibility of suppressing the cough reflex constitutes the so-called cough discipline, often practiced in sanatoriums for tuberculous patients. The patient is constantly impressed that he should not respond to every cough impulse with the cough reflex. Through gradual training, it is possible to raise the threshold of irritation and decrease, and sometimes completely rid the patient of painful coughing attacks. In frequency and importance, first place should be given to C. caused by diseases of the respiratory apparatus. First of all, it is necessary to note C. in diseases of the nose (polypoid growths, inflammatory swellings of the mucous membrane, etc.). With difficulty in nasal breathing, patients are forced to breathe through the mouth and, consequently, by inhaling unheated air, constantly subject the laryngeal mucous membrane to irritation. During sleep, the secretions of the pharyngeal mucous membrane descend along the posterior or lateral wall of the pharynx and often irritate the larynx, causing the cough reflex. Catarrhal condition of the larynx or the mucous membrane below the vocal cords (laryngis subcordalis in children under 4 years) is a frequent cause of barking cough. In these cases, deep spasmodic breathing, laughter, yawning intensify C. The latter is often intensified during physical work due to hyperemia of the inflamed laryngeal mucous membrane. Isolated disease of the trachea is a rare phenomenon, therefore the appearance of pure tracheal cough is observed only in cases of rupture of the mediastinal gland or growth of cancerous masses from the esophagus. All these rare cases are manifested by the sudden appearance of severe intractable cough. Much greater importance is attached to the so-called bifurcational C. The bifurcation possesses exceptionally high sensitivity. The cause of the cough reflex of this area of the respiratory apparatus can be imagined as an inflammatory process in the region of the bifurcation. An inflammatory reaction is often seen in influenza, which as is known causes swelling, redness, sometimes hemorrhages in the upper respiratory tract. Foreign bodies lodged in this place also cause persistent, high-pitched C. But bifurcational C. can also be the result of processes occurring in the mediastinum. These processes (new growths, aneurysm), by compressing the bifurcation, cause stagnation of secretions, and thus constantly maintained irritation leads to characteristic, persistent and non-productive C. Such persistent, dry cough sometimes resembles the characteristic symptom complex in whooping cough. Not only in children but also in adults, a C. continuing for weeks with noticeable redness of the face, mainly at night, sometimes accompanied by vomiting at the height of C. with characteristic tickling in the throat, is suspicious for whooping cough. In various forms of bronchitis, C. is a constant companion; in these cases it can be dry and moist. Particularly persistent C. is encountered in diseases of the small bronchi, the mucous membrane of which has high sensitivity and is the site of origin of the cough reflex. Usually such a catarrhal condition rarely remains isolated, since the large bronchi and trachea, constantly being irritated by secretions from the small bronchi, are also drawn into the inflammatory process. Basal limited bronchitis, accompanied by persistent C., should cause the physician to pay attention to the possibility of a subdiaphragmatic process (abscess of the liver, cholelithiasis). A suddenly begun, persistent, spasmodic C., accompanied by scanty secretions, is often the first symptom of a new growth of the bronchus, hydatid of the lung. It is important to note that in miliary tbc due to irritation of numerous endings of the branches of the n. vagus, a dry, non-productive C. is observed. And finally, painful, dry C. accompanies, almost as a rule, diseases of the pleura (dry pleurisy, new growths of the pleura). A number of infectious diseases (influenza, measles) proceed with a marked reaction from the respiratory apparatus; but also in other infectious diseases (e.g., in typhoid fever) the cough symptom is sometimes so sharply expressed that it can lead to diagnostic error, since such patients are treated for a long time as suffering from influenza. In second place in importance as a symptom is C. in diseases of the heart. Diseases accompanied by insufficiency of cardiac function and causing thereby hyperemia of the lung are accompanied by C., mainly at night. Such cardiac C. is especially frequently observed in mitral stenosis. This is such a frequent symptom that many authors consider it characteristic of this defect. Often this C. (as well as in aneurysm and in sclerosis of the aorta) is accompanied by a sensation of scratching, dryness, a sensation of a foreign body in the throat. These phenomena must be explained by irritation of the n. laryngei sup directly or through rami communicantes. As is known, edema of the lung due to insufficiency of cardiac function is usually accompanied by severe C. and the secretion of serous sputum resembling egg white, often colored with blood. It should also be pointed out that C. which accompanies in patients suffering from extrasystole almost every extrasystole. It has already been pointed out above that diseases of the mediastinum are the cause of persistent and dry C. It is necessary to note that irritation of the n. vagus in the mediastinum is possible due to various pathological processes (malignant and benign new growths, swelling of lymphatic glands of various etiologies, dry mediastinal pleuritis); all these processes can cause spasmodic, whooping cough-like C., which is accompanied by cyanosis of the face, hyperemia of the brain, often hemorrhages into the conjunctiva and nasal bleeding.--Special mention should be made of C., which is sometimes observed in patients in connection with taking food. Such patients after eating begin to cough strongly, and usually this C. brings the patient to vomiting. This C. is explained by irritation of the n. vagus. The reflex from the n. vagus must also explain the C. observed with irritation of the external auditory canal (ram. auricul. n. vagi). Cases of 'hepatic' C. are undoubtedly also observed, mainly in abscess of the liver.

Such a cough is explained by irritation of the sensitive nerve endings of the Glisson capsule or by accompanying diaphragmatic pleurisy. C. in these cases takes on a convulsive character. What has been said in relation to the liver must be applied in equal measure to the spleen. C. due to inflammatory processes in the female genital sphere occurs extremely rarely, mostly in nervous women suffering from diseases of the respiratory apparatus (increased excitability of the center of the cough reflex arc). Even rarer is the so-called nervous C., the diagnosis of which is permissible only in exceptional cases. In practical life, a wet and dry C. are distinguished. In the first case, the cough takes on a special timbre, because secondary noises are added to the cough impulse due to the movement of bronchial secretions. In dry C., the secretion is absent or it is so viscous that it is not set in motion; therefore such a dry C. has a different timbre. For practical purposes, it is also important to distinguish a barking C., which is observed in swelling of the vocal cords (simple and croupous laryngitis). Very often such a C. is accompanied by aphonia. Hoarseness of voice sometimes accompanies a rough C., the cause of which should be sought in deposits of secretion on the vocal cords or in their destructive changes. A completely soundless C. occurs in destruction of the vocal cords or in paralysis of the muscles closing the glottis. A dull C. (resonance in large cavities) can be found in severe pulmonary patients with sharply expressed destructive changes in the pulmonary parenchyma.