454 



TRACHEOTOMY. 



easily carried out with a little care. Its success depends greatly 

 on the cannula used. 



Many of those recommended can only be employed in connection 

 with their appropriate tracheotomes, and, therefore, may be disregarded. 

 The oldest (Barthelemy's) consists of a metal tube, 4 to 8 inches in length 

 and | to 2 inches in width, bent at one end, and provided with a plate to 

 hold it in position. The bend must be confined to the upper end, and 



a, v c 



Fig. 358. — Position of tracheal cannula, a, Normal; b, when too much curved 

 c, when insufficiently curved. 



must be suited to the thickness of the parts between the skin and front 

 wall of the trachea. Where the bend is too short, not only will the skin 

 and muscular tissues be bruised, but the lower end of the tube will press 

 against the posterior wall of the trachea and produce inflammation with 

 proliferations, leading to stenosis (Fig. 358, c). Where the bent portion 

 is too long, there is undue space between the plate and the skin, and if 

 such a tube be pressed home by tapes or straps, it becomes displaced and 

 liable to injure both walls of the trachea (Fig. 358, b). Tracheotomy tubes, 

 formerly made of tin-plate, are now much better manufactured of German 

 silver. 



The objection to Barthelemy's cannula, viz., that it falls out easily, 

 may partially be obviated by straps (with buckles), fastened in the eyes 

 of the plate and passed round the neck. They should not be carried too 

 far forward, as the tube is then liable to fall out during coughing or violent 

 expiratory movements. Barthelemy's tube somewhat disfigures the 

 animal, and where used for long periods very careful fitting is necessary 

 to prevent thickening and narrowing of the trachea. Occasionally, owing 

 to the strap breaking and the tube falling out during the night, the horse 

 has been found dead. This tube is therefore now seldom used for permanent 

 wear. To overcome the above disadvantages models have been designed 

 by Leblanc, Degive, Vachetta, Peuch, Field, Coleman, Jones, and others. 

 Dispensing with the use of straps lessens disfigurement without interfering 

 with the secure fixing of the cannula, and diminishes risk of bruising and 

 irritation. The trachea remains unobstructed in an upward direction as 

 far as the larynx, whilst the cannula is very easily cleaned. Leblanc has 



