TRACHEOTOMY By the operation of tracheotomy one under stands, not only incision of the trachea, but the fixation into it of some appliance through which a free passage of air is obtainable.
Tracheotomy is performed to facilitate respira tion when this is seriously impeded by the existence of any abnormal condition in the air passages above the usual seat of operation. Tracheotomy is undertaken both as a temporary and as a permanent measure. It is performed as a temporary measure for the relief of dyspncea resulting from obstruction due to some acute pathological condition of the larynx or upper air passages, or when necessary to enable the performance of an operation involving any part of these. It may also be performed to enable the carrying out of the necessary correction in malpresentation occurring in difficult parturi tion, if the straining of the parent is so severe that this cannot otherwise be accomplished: by nullifying the closure of the glottis the extra pressure to be obtained by fixation of the diaphragm with the lungs fully distended is unobtainable.
The operation is performed as a permanent measure when chronic obstruction to the free passage of air exists; in a few cases in which the obstruction continuously impedes respira tion, but in a majority of cases in which respira tion is impeded only during exertion.
Although the operation is performed as a temporary measure on the majority of the domestic animals, it is much more frequently performed upon the horse than on any other; and it is almost solely upon this animal that it is undertaken as a permanent measure. The operation upon the horse will be described, and although the operation upon other animals is rendered slightly more difficult owing to the less prominently situated trachea, it is precisely similar in surgical respects.
Since the part of the trachea involved in the operation—the upper third—is readily exposed without mutilation of any vitally important tissue, a detailed description of the anatomical structure other than that mentioned in describ ing the operation itself is unnecessary.
The choice of the exact place in the upper third of the trachea at which to insert the tube depends upon varying circumstances: the existence of disease, conformation, and whether the operation is performed as a temporary or as a permanent measure.
In urgent cases it may be necessary to per form the operation comparatively low down the trachea, either on account of oedema or cellulitis about the larynx and upper part of the trachea, or if dyspncea is very marked. In the latter case it is inadvisable to attempt to raise the head, for any slight disturbance may be sufficient to so aggravate the difficulty in respiration as to cause the animal to stagger or fall and be a danger to the operator. Such cases leave little choice to the surgeon in regard to instruments, technique, or position, the necessity for immediate relief far outweighing all other considerations.
A general rule to be observed in tracheotomy is that it shall be performed as high up the trachea as possible. The observance of this rule is more important when the operation is performed to insert a tube for permanent use. The most suitable position is at about the third, fourth and fifth tracheal rings, and in some cases it may be performed at even the second and third rings. In horses of the heavier breeds having short thick necks and little or no curvature between the submaxillary space and the front upper portion of the neck, it is not possible to place the tube quite so high.
There is no disadvantage in this high position. There are many reasons for adopting it. The longer course the air has to traverse on its way to the lungs is advantageous; the tube having a more downward than forward direction, the entrance of foreign bodies into the trachea during locomotion is less likely, e.g. dirt and other material thrown up by a horse in front while galloping; the tube is less likely to become caught or hung up, and injury to the trachea result, such as might happen by the tube becoming fixed on a manger, rail or rope; and if after a time excessive granulations or any other trouble should become so severe as to render impossible the maintenance of the tube at its original position, the operation can be repeated lower down.
Instruments.Tracheotomy tubes of various patterns have been devised. The simplest is a curved metal tube having at one end a wide oval flange, at the opposite extremities of which are cut two slots from which tape fastened round the neck holds the tube in position. The latest pattern tube is made in several pieces, which when adjusted in position render it self-retaining. This latter type of tube is in variably used when a tube is required for a permanency, and although the former type of tube—slightly varied in pattern, the tube part being flattened or elliptical in cross-section—is still used in some cases in which a tube is required temporarily, one of the simpler self retaining tubes is just as or even more satis factory. Occasionally, however, the operation has to be performed in such urgent circum stances that no tube of any pattern is at hand. The contrivance of some means whereby the incision into the trachea may be maintained patent until a proper tube can be obtained and inserted is left to the ingenuity of the operator, but in case of emergency a tea- or coffee-pot spout, or a piece of strong wire suitably bent, may be employed for this purpose.
The essential points of a tracheotomy tube are: that it is made of some metal that does not corrode; that it is strong and large enough to admit a sufficient supply of air, but not too heavy or cumbersome; that it is readily cleaned; that it is easily inserted; and that it is secure and firm when placed in position. The most essential feature of a tube for per manent wear is that it fits exactly the opening into the trachea after the primary inflammatory swelling has subsided, both as regards the length from the skin to the inside of the trachea, and as regards the coming into contact with every part of this passage. Jones's tracheo tomy tube (Fig. 291) is constructed on lines that enable it to meet these requirements. Arnold's improved Nelson (Fig. 292) is a similar tube. These tubes are of very similar pattern, and are the most suitable for permanent wear. They are made in various lengths and diameters. Each tube consists of four pieces: parts 1 and 2 are flanged, and are inserted, one at the bottom of the opening into the trachea and one at the top of it; part 3 is placed between parts 1 and 2, and when pushed home renders the tube securely held by keeping the flanged portions apart. This third piece has a pro jection at each side of its inner extremity. These projections prevent the ends of the divided tracheal ring from overlapping the inner opening of the tube and curling into the lumen of the trachea. Part 4 is a plug for the external opening of the tube. It should be maintained in position except when the animal is at exercise or work. Gibson's tube is similar in structure to the two already named, but has in addition a valvular arrangement in the lumen of the central or third piece. The valve, which consists of two semicircular metal leaves, opens inwards, allowing for inspiration by the tube. The valve closes on expiration, in which, as a result, the air escapes by the natural passages.
For temporary use, a Field's pattern tube (Fig. 293) is quite suitable. This tube is made in two pieces, similar in structure and consisting of a wide flat oval flange, from the centre of which passes backwards a short round tube which has a half-round long curved lip. The curved lip and tube of part 2 pass through part 1 so that the flanges lie directly super-imposed to each other, and the lips curve in opposite directions. The two pieces are held together by a movable clasp on part 1. This is not a suitable tube for perma nent wear, be cause, owing to the divergence of the two lips, and the other wise loose fitting of the tube, granulation FIG. 293. Field's tracheotomy tube. tissue forms, and soon bulges into the lumen of the tube. For temporary use, however, this tube is quite satisfactory.
A little difficulty is often experienced in inserting a temporary tracheotomy tube when the opening into the trachea has been made by simple longitudinal incision through one or more of the tracheal rings. If a Field's tube, or one of similar pattern, is being used this difficulty can be obviated by holding the part being first inserted sideways so that the lip of the tube can be directed lengthwise through the incision; then by giving the tube an inward and downward twist it assumes its proper position. The remaining part is inserted similarly, but with an inward and upward twist.
Various tracheotomes have been devised for removing the portion of the trachea in order to accommodate the tube.
Spooner's tracheotome (Fig. 294) is an instru ment similar in form and in application to a pair of ordinary compasses, the extremity of one arm being in the form of a scalpel. The FIG. 294. Spooner's tracheotome.
arms have an adjustable screw by which the instrument is set to cut a circular piece of the required size from the trachea.
M`lienny's tracheotome is a very much heavier instrument. It has a hinged disc-shaped knife, which by means of a thumbscrew working on a threaded spindle is protrusible from and retract able into a circular"wad-cutter"shaped knife. The disc-knife is passed transversely between two of the tracheal rings into the lumen of the trachea. On tightening up the screw the disc knife, which has assumed a position at right angles to its spindle, is drawn within the circular knife. completely severing a piece of the trachea.
If it were necessary, or in any way advisable, that the opening into the trachea should be a precise geometrical shape, then, regardless of their disadvantages, the use of such instruments would be justified. There is, however, no necessity for the opening to be exactly circular. More freedom of judgment as to the exact portion and amount of the tracheal rings to be removed is possible by using a knife guided by hand than by using a fixed mechanical cutter. And further, since the operation is not performed under a general anaesthetic there is always a chance—a probability rather that the animal will prove restive just when the instrument is fixed in position and the cutting incomplete. Serious injury might result, especially if the instrument is at all cumber some or heavy. A really serviceable retractor is much more conducive to the neatness and ease with which the operation can be performed. Fig. 295 illustrates one used by the writer, and Fig. 296 shows it in position. The hooks are fixed on to the ends of a buckled strap which passes round the animal's neck. The retractor can thus be adjusted to any sized neck, and by reason of pieces of strong elastic, interposed between the hooks and the ends of the strap, an even pressure is maintained during any movement of the animal's neck.
Other instruments required are: a scalpel, a probe-pointed bistoury, a tenaculum hook, having a barb on it like that of a fish-hook, or in place of the latter a pair of vulsellum forceps, dissecting forceps, scissors, and several pairs of artery forceps.
Preparation.The hair on the front upper third tracheal region should be clipped short and the skin of this area painted with tincture of iodine. A combined local anaes thetic and haemostatic is then injected subcutane ously and submuscularly at the exact seat chosen for the operation, and a suitable time allowed for anaesthesia to be pro duced. During this time an area of skin some 15 cm. long by 10 cm.
wide over the seat of the operation may be shaved and redisinfected. Shaving, however, is by no means necessary, provided the hair is cut short and the area well disinfected.
Operation.The operation should be carried out under strict aseptic conditions when pos sible, and upon the animal in a standing posi tion. The head is raised slightly, just suffi ciently to allow the operator to gain access to the trachea. The head should not be raised excessively, because this not only tends to upset the animal, but by considerably altering the relative positions of the trachea and the over lying skin, will cause some puckering of the latter when the head resumes its normal posi tion. This puckering of the skin, even when the head is only slightly raised, is prevented by removing the lowest part of the exposed portion of the trachea. The animal should be backed into a corner where there is a beam over which a cord can be placed and used for raising the head in a similar manner to that followed in drenching. The cord should have a wide webbing loop at the end. This loop is threaded down inside the nose-band of the head-stall and placed under the lower jaw, not in the mouth. A sling made of a stable rubber can be used and the cord tied to this. If the animal's head is raised in this manner and not too high and a local anaesthetic used, no other form of restraint is as a rule necessary. A twitch in the majority of cases causes more annoyance than benefit.
The skin is rendered tense over the seat of the operation by the thumb and fingers of the left hand, and an incision from 5 cm. to 6 cm. long made through it with the scalpel, the direction of the incision being from above down wards. The subcutaneous connective tissue and the thin layer of the panniculus carnosus muscle are then divided, thus laying bare the muscular tissue. The retractor is now adjusted to the lips of the skin wound, and with such tension that a more or less square opening will be presented. Any remaining connective tissue overlying the muscles is easily and quickly removed. This removal of the loose connective tissue so as to lay quite bare the underlying muscles, and a clear understanding of the anatomical relationship of the latter, are neces sary to avoid injury and to ensure that the tube will occupy a menial position when the operation is completed.
The muscles exposed are the right and left hyoid portions of the sterno - thyro - hyoideus muscles, and the right and left subscapulo hyoideus muscles. The former occupy the middle position, and are in intimate apposition to one another, 'the line of demarcation between the two being very indistinct. The latter occupy a lateral position, the right and left muscles do not come together in the middle line, but they are closely applied to the external side of the first-mentioned muscles, the lines of demarcation being slight but distinct. Division along one or other of these lines is often practised in mis take for its being the middle line; this causes the tube to take a slight tilt to one or other side. If the line of apposition of the muscles cannot be made out, separation of the muscular fibres along a line equidistant from the lateral lines referred to is made, care being taken to avoid cutting the muscle fibres unnecessarily. Separa tion is continued till the trachea is exposed, and is extended a little further than the lower limit of the skin. incision. The separated muscles are now included in the retractor, and the inner free edges of two underlying muscles come into view. These muscles are freed from the trachea and included in the retractor; and any loose connective tissue immediately overlying the exposed portion of the trachea is dissected away.
Procedure now varies somewhat according to whether the operation is for a temporary or a permanent purpose. If temporary, the trachea is incised only; usually a mesial longitudinal incision is made through one or more rings and the tube inserted; or if a tube, flatly elliptical on section, is to hand, it may be inserted through a transverse incision in one of the inter-annular ligaments. If the operation is for a permanent measure, then part of the trachea is removed.
When a portion of the trachea has been excised there is a tendency to collapse of that part of it containing the mutilated rings. This tendency to collapse is in great part due to the normal incompleteness posteriorly of the tracheal rings, and though of no consequence as long as a well-fitting tube is in position, it may lead to serious trouble if a small ill-fitting tube is used, or if it is desired to remove the tube and allow the opening to close. Various opinions have been expressed as to the precise amount of the tracheal rings that should be removed in order to prevent or minimize this result. The amount removed depends necessarily upon the size of the tube that is inserted, and also upon the width of the tracheal rings, which varies in different animals and even in the same animal. If a Field's tube is used the whole width of a portion of one ring, or a part of two rings and the intervening inter-annular ligament, will suffice; but if a tube of Arnold's improved Nelson or similar pattern is employed, then the complete width of one ring will be in sufficient, and if parts of the width of two rings—at least two-thirds of the width of each will be necessary, to prevent undue pressure on them by the tube—are removed, these rings will be so weakened anteriorly that collapse and deformity will not be prevented. In the writer's experience the removal of the whole width of a portion of one ring is attended by the least serious results, provided the rings on each side of it are left sufficiently strong to maintain their normal shape. He therefore removes the whole width of a portion of one ring, the inter-annular ligaments on each side of it, and a part of the width—about one-third —of the ring next above and that next below. A slight disadvantage of this method is that the ends of the divided ring tend to catch on the inner projections of the third or central piece of the tube when it is being inserted. If, however, sufficient of the ring has been removed and the tube is carefully inserted for a day or two until these more or less free ends of the divided ring are healed over, no trouble will occur.
The removal of the portion of the trachea is carried out as follows: The scalpel is passed through the lowestvisible inter-annular ligament, making a transverse incision about 2 cm. long. The barbed tenaculum is passed through this opening, given a quarter turn, and hooked through the middle of the tracheal ring next above. Vulsellum forceps may be used in place of the tenaculum, but they are not so handy for maintaining a continual hold on the piece of the trachea which is removed. Holding the tenaculum firmly, but lightly, with the left hand, the end of the probe-pointed bistoury is passed through the incision and the latter carried out to about or 2 cm. from the mesial plane. The edge of the knife is then turned upwards and at right angles to its former position, and the tracheal ring above it cut through by a sawing motion—the cutting pressure being exerted when drawing on the knife rather than when pushing on it. The incision is carried on through the next inter annular ligament and continued to the left in a curved direction, so that a segment is cut away from the next ring, the width of the segment at its middle part being a third the width of the whole ring. The edge of the bistoury is now from to 2 cm. to the left of the middle line, and by cutting perpen dicularly downwards the ring already severed on the right and the ligament below it are cut through; then by turning the edge of the knife to the right a portion of the next ring, similar to that removed from the top ring, is cut away, and the piece of trachea required to be removed is thus completely freed.
This cutting away of the piece of the trachea can be carried out in a clockwise or anti clockwise direction, whichever suits the operator.
The retractor is removed and the tube at once placed in position and the animal's head lowered. The ha3morrhage, which is slight and almost solely from the cut mucous membrane lining the trachea, invariably causes a certain amount of coughing, and it is for this reason that the head should be lowered as soon as possible in order to enable any blood to be more freely expelled.
During the first few days there is bound to be more or less swelling of the tissues surrounding the seat of operation. To allow for this swelling the tube inserted should be about 1 to cm. longer than the thickness of the tissues from the skin to the inside of the trachea when the head is held in the normal position, otherwise the compression of the mucous membrane lining the trachea by the inside flanges of the tube may be so great as to cause necrosis of the membrane; and if this occurs, granulation of it will follow, which may be troublesome to deal with. The external flange may also exert a similar effect upon the skin, and in addition there may be some difficulty in replacing the tube when it has been removed for cleaning purposes.
The tube should be removed and cleaned daily for the first week or ten days. This cleaning must be done as expeditiously as possible, owing to the rapid contraction of the opening into the trachea when the tube is not in position. A second clean tube may be employed, so as to enable a more thorough cleaning and disinfecting of the used tube.
The removing and replacing of the tube should be done by some one who realizes the necessity of its being done carefully in order that no scratching of or injury to the tissues shall occur, and that the tube shall be correctly replaced. A mild antiseptic should be used for cleansing the wound, and any excess in granula tion of it should be immediately controlled by light cauterizing; a 5 per cent solution of chloride of zinc answers admirably, but it must be applied cautiously, so that no excess of the fluid runs off the raw surfaces.
The greater part of the inflammatory swelling will have subsided in about ten days' time, and a tube should then be fitted to the exact require ments of the throat. This latter tube when once adjusted should not be removed more frequently than is necessary. It should be allowed to remain in position for increasingly longer periods, until it can be worn continu ously for several months. The plug should be removed and any accumulated mucus cleared from the inside passages of the tube by means of a smooth spatula-like instrument, injury to the mucous membrane at the back of the trachea being avoided.
Excessive granulations of the mucous mem brane and septic chondritis of the tracheal rings, the bugbears of tracheotomy, are more easily prevented and controlled by the exercise of special attention to the throat immediately following the operation, by the selection and fitting of a good pattern tube, and by not irritating the tissues by continual removal of the tube, no matter how carefully the latter is done, than by any particular method in per forming the operation itself. E. B. R.