FRACTICAL CONSIDERATIONS: THE AIR- PASSAGES. 1841 



Tracheotomy may be required for obstruction in the larynx or above it, for the 

 removal of foreign bodies, or as a preliminary step in other operations, as excision 

 of the tongue. 



It may be done at any point between the cricoid cartilage and a short distance 

 above the suprasternal notch. The difficulties of the operation increase with the 

 distance from the cricoid because (a) the depth of the trachea from the surface in- 

 creases as it approaches the thorax ; (^b') it is more movable ; (r) it is more com- 

 pletely covered in by the sterno-hyoid and sterno-thyroid muscles ; (^ ) it is more 

 apt to be overlapped by the common carotids ; or (/) crossed by the left common 

 carotid when it arises from the innominate artery ; or by (/") various venous trunks, 

 as the transverse branches between the anterior jugulars, or the inferior thyroids, or 

 even by the left innominate vein, which, — lying as it does in front of the trachea, — in 

 the presence of venous congestion, may extend above the level of the top of the 

 sternum. Moreover, in children under two years of age the upper edge of the vas- 

 cular thymus gland may lie in front of the trachea at the root of the neck. The in- 

 nominate artery itself or the thyroidea ima may occupy the same position. 



For these reasons tracheotomy is done with comparative rarity below the level 

 of the isthmus, which lies in front of the second, third, and fourth tracheal cartilages. 

 The incision is made with tfie head in full extension so as to lengthen the trachea, 

 steady it by increasing its tension, and bring it nearer the surface. The chin, thyroid 

 angle, and suprasternal notch should be in the same line. The incision should be 

 exactly in this line, extend about two inches downward from the cricoid, and divide 

 the skin, platysma, and fascia and expose the interval between the sterno-hyoid and 

 sterno-thyroid muscles, which may be separated by blunt dissection. The pretracheal 

 fascia is then divided, exposing the upper ring of the trachea and the thyroid isthmus. 

 The isthmus may be depressed to give more room for the tracheal opening, or may, 

 after ligation on both sides, be di^'ided in the mid-line, where, as Treves says, it, 

 like other median raphes, has but slight vascularity. A large communicating branch 

 between the superior thyroid veins often runs along the upper border of the isthmus, 

 and over its anterior surface there may be a plexus made up by the branches of the 

 thyroid veins of the two sides. These vessels, if present, may be dealt with sepa- 

 rately or may be picked up with the two sides of the divided isthmus in the grasp 

 of heavy haemostatic forceps, which by dropping over the neck raise the trachea 

 into the wound ( Pearce Gould). 



The trachea is then seen and felt, steadied and made still more superficial by 

 upward traction by a small, sharp hook thrust into the lower edge of the cricoid, and 

 opened exactly in the middle line by a bistoury thrust in at about the level of the 

 third or fourth ring and made to cut upward to about the first. 



In very fat or very muscular persons the depth of the trachea is increased. 



In children its small size, its shortness (one and a half inches in the neck in a 

 child of from three to four years of age), its mobility, its depth (on account of the 

 considerable quantity of subcutaneous fat usually present), the compressibility of its 

 thin cartilaginous rings, the height to which the great vessels may rise in front of it, 

 the venous engorgement usually present, and the occasional interposition of the 

 thymus (^vide supra), all increase the difficulties of the operation. 



Foreign bodies in the air-passages are most likely to be arrested at the upper 

 laryngeal opening, at the ventricle or the glottis, at the bifurcation of the trachea, 

 or in the right bronchus. They are apt to enter that bronchus instead of the left 

 because {a) the right lung is larger (the left being encroached upon by the heart) 

 and there is a greater intake of air and a stronger current ; (c5) the right bronchus 

 has the larger transverse diameter ; (f) it is less horizontal and therefore more 

 directly a continuation of the trachea than the left bronchus (page 1838); and (^) 

 the carina tracheae is situated to the left of the middle line in the majority of cases 

 (page 1837). If small enough, they may be drawn into some of the lesser bron- 

 chioles by the inspiration — usually sudden — which has caused their entrance into the 

 air-passages. The immediate symptoms are always those due to obstruction of the 

 air-current, either mechanical — from the size of the foreign body — or reflex, as when 

 spasm of the glottis is excited by the irritation of the superior laryngeal or tracheal 



nerves. 



116 



