Chronic Laryngitis. This may follow the acute form or it may come on independently and by slow degrees. It may accompany nasal catarrh, or chronic bronchitis. Old animals which have had heavy draught work and repeated attacks of sore throat, are frequent subjects of it, and as Fergusson has pointed out it is most prevalent among horses whose throats have been compressed by the inconsiderate use of the bearing rein. Reynal has observed it often in horses that are sweated with difficulty, and in those which remain long wet from the length and thickness of their winter coats.
Symptoms. When acute laryngitis passes into the chronic form all the symptoms subside except a slight nasal discharge, the cough, tenderness of the larnyx, and roaring. The cough is dry, short, and hacking, rarely soft, and is heard mainly when the animal feeds, when he leaves the hot stable for the cold air, and after drinking cold water. During exercise, it is equally excited, the cough becoming harder, and the horse extending his head and neck as if to disengage some body from its throat. The subject may in nearly all other respects maintain the appearance of vigorous health.
Course, etc. This disease is liable to prove obstinate and if of old standing, often incurable. Unless checked, the continued congestion and irritation of the larynx, the frequent, hacking cough, and the consequent violent distension of the lungs bring about extensive and irreparable structural changes. Among these may be mentioned ossification of the cartilages of the larnyx; paralysis of the left laryngeal nerve with wasting of the muscles to which it is distributed, and roaring; dilatation of the bronchial tubes, and permanent distension and rupture of the air cells (emphysema, broken wind, heaves).
Treatment. Acute form. Unless in the very mildest cases unaccompanied by fever, repose is essential. If available, a roomy, clean, dry, and airy loose box should be allowed, care being taken to avoid draughts of cold air and to secure a soft equable temperature neither too hot nor too cold. Blankets should be used and even flannel bandages applied loosely to the legs if the weather is cold, or, if there is any tendency to chills and shivering. The nostrils must be steamed as directed for coryza. A piece of sheepskin with the wool turned in may be tied around the throat and up to the ears. In very acute cases a linseed meal poultice or wet pack may be applied to the throat, while in the milder forms, a mustard poultice or a lotion of Spanish flies or other stimulant may be employed. Unless the malady has an epizootic type, with prostration and a weak, rapid pulse, the bowels may be opened by a laxative (3 or 4 drachms, aloes), and the water or gruel the animal daily drinks should contain ½ to 1 ounce nitre. As an expectorant the patient may take salammoniac 1 oz. daily in the drinking water, or this agent may be evaporated from a clean chafing dish every two hours and inhaled. Or he may take carbonate of potash or soda, or iodide of potassium. If the cough is troublesome, half a drachm of Dover’s powder may be given thrice a day or 1 grain chloride of apomorphine every hour. Bromide of potassium or sodium may also be resorted to. Inhalations or spray of sulphurous acid, or vapor of oil of turpentine and insufflations of calomel may benefit as local applications. The diet must be confined to sloppy bran mashes, cut roots, or boiled barley, or oats. Hay should be withheld in the more acute cases until improvement appears. Under treatment such as the above and even without the medicinal part of it, the great majority of cases will do well.
In cases attended with high fever with strong full pulse and bright red nasal membrane, the purgatives and diuretics are especially called for, and the former should have their action encouraged by frequent hot water injections. Twenty drop doses of the tincture of aconite repeated four times a day, or ten drops every three hours, will be further useful.
When the symptoms are of such a type as portend the access of paroxysms of threatened suffocation, bleeding has been strongly recommended, but unless resorted to in the first twenty-four or forty-eight hours is rarely admissible. Also in weakened constitutions and when the fever is of a low type, with small, weak pulse and general dullness and prostration, the temporary relief obtainable from bloodletting will not often counterbalance the danger of increasing weakness, and the loss of recuperative power. In all such cases the application of a strong mustard poultice for several hours in succession, until an abundant effusion has taken place, into the skin and beneath it, has often the best effect by virtue of its depletive and derivative action. Active friction of the limbs to improve their circulation and increase their temperature is also useful.
Tracheotomy. When suffocation becomes imminent not a moment must be lost in performing tracheotomy. This operation is always available in threatened suffocation from obstruction to the passage of air in the nostrils and throat.
Different methods of opening the windpipe have been resorted to. One is by means of a cannula and trochar at least three-fourths of an inch in diameter and about five inches long and with two large oval orifices in the middle of the cannula, and on opposite sides. This is made to transfix the windpipe with its investing skin and muscles from side to side in the middle of the neck, care being taken to pass it in the interval between two adjacent cartilaginous rings. The trochar is now withdrawn and the orifice in the cannula corresponding to the interior of the windpipe, the animal is enabled to breath freely through the tube. The cannula has only then to be secured in its place by a tape carried round the neck.
The more common plan is by introducing a tube through a circular opening made in the trachea. For this operation are needed, scissors, knife with a thin narrow blade, needle and thread, and tracheotomy tube. The common tube is about an inch in diameter, four to five inches long bent upon itself so as to fit into the trachea, and furnished with a flat shield to slits in which cords may be attached to fix it in its place. A second variety is only long enough to reach into the windpipe. It is provided with a flattened shield externally and from its inner extremity projects downwards at right angles a plate curved so as to adapt it to the form of the interior of the trachea. There is an additional plate to fit into the upper part of the tube, provided with two lips projecting from it at right angles; the outer lip is screwed to the shield after the tube has been introduced into the wind pipe and the inner lip is thus fixed inside the ring of the trachea, immediately above the opening and effectually prevents any displacement of the tube.
In operating the animal is kept standing with the head as nearly as possible in the natural position. The hair is removed from the skin beneath the windpipe between the middle and upper thirds of the neck. The skin having been rendered tense, (without displacement) by the fingers and thumb of the left hand, an incision is made in the median line from above downwards, for about two inches and is carried through the muscles so as to expose two rings of the trachea. The needle and thread are passed through the membrane connecting the two rings, and with the knife a semi-circular piece of cartilage is cut from each of the two adjacent rings. The thread in the connecting membrane prevents them from being drawn in by the rush of air. It only remains to introduce the tube and fix it in position.