Anatomy of Tracheostomy

7/27/2019 Anatomy of Tracheostomy

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Related Questions:

Anatomy of tracheostomy, cricothyrotomy... Describe the anatomy of the larynx. What is the nerve supply? Candidates must be able to demonstrate their knowledge of practical invasive

procedures, with an understanding of the principles and hazards involved.

Emergency airway management including tracheostomy Describe the technique of percutaneous tracheostomy, including all the relevant

anatomy. What are the complications?

Anatomy of the larynx

The larynx is a valve separating the trachea from the upper aerodigestive tract. It is

primarily thought of as an organ of communication but it is also an important regulator of

respiration, and is necessary for an effective cough or valsalva manoeuvre, and prevents

aspiration during swallowing.

Skeleton

Hyoid bone - attachment to epiglottis and strap muscles. Thyroid cartilage - anterior attachment of vocal folds. Posterior articulation with cricoid

cartilage.

Cricoid cartilage - complete ring. Articulates with thyroid and arytenoid cartilages. Arytenoids - two cartilages which glide along the posterior cricoid and attach to

posterior ends of vocal folds.


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Divisions

Supraglottis - usually covered with respiratory epithelium containing mucous glands. Epiglottis - leaf-shaped mucosal-covered cartilage, which projects over larynx. Aryepiglottic folds - extend from the lateral epiglottis to the arytenoids. False vocal cords - mucosal folds superior to the true glottis. Separated from true

vocal folds by the ventricle.

Ventricle - mucosal-lined sac, variable in size, which separates the supraglottis fromthe glottis.

Glottis - the true vocal folds attach to the thyroid cartilage at the anteriorcommissure. The posterior commissure is mobile, as the vocal folds attach to the

arytenoids. Motion of the arytenoids affects abduction or adduction of the larynx. The

bulk of the vocal fold is made up of muscle covered by mucosa. The free edge is

characterised by stratified squamous epithelium. The vocal folds abduct for inspiration

and adduct for phonation, cough and valsalva.

Subglottis - below the vocal folds, extending to the inferior border of the cricoidcartilage.

Innervation

Branches of the vagus nerve. Superior laryngeal nerve - sensation of the glottis and supraglottis. Motor fibres to

the cricothyroid muscle, which tenses the vocal folds. This nerve leaves the vagus high

in the neck.

Recurrent laryngeal nerve - sensation of the subglottis, and motor fibres to intrinsicmuscles of the larynx. This nerve branches from the vagus in the mediastinum, thenturns back up into the neck. On the right, it travels inferior to the subclavian artery,

and on the left, the aorta.


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Equipment: The percutaneous tracheostomy set illustrated is manufactured by Portex,

although other sets are available. It consists of a Seldinger-type needle and wire, over which

a guide and then a single one-step dilator is passed. In addition to the equipment given, one

also needs :

Sterile field and cleaning fluid

Lubricating jelly

Local anaesthetic with adrenaline

Tracheal dilator

Fibreoptic laryngoscope/bronchoscope

Catheter mount to accept scope

Intravenous anaesthesia

One-step percutaneous tracheostomy kit

Airway management

Although inhalation anaesthesia is possible, a total intravenous technique provides

much smoother anaesthesia and better conditions for performing the bronchoscopy and

tracheostomy. A combined propofol and opioid technique is a favoured option. Full monitoring

is instituted, and ventilatory parameters altered during the bronchoscopy to maintain

adequate oxygenation and end-tidal CO2 levels.

Following induction of anaesthesia, the patient is prepped and draped. The bronchoscope is

passed through a tracheal tube and the anatomy of the airway visualised. The aim of the

fibreoptic scope is to ensure correct initial placement of the introducer needle, in the midline

and through the second or third tracheal rings. Subsequent to this, it will monitor dilation of

the trachea, and ensure that the introducer does not remain in the trachea.

Landmarks

Although not necessary for the procedure, information from

bronchoscopy is very useful and it should always be used when

learning the technique.

The patient is positioned with the neck extended, with an intravenous

fluid bag between the shoulder blades and the head in a head ring.

This brings as much of the trachea as possible into the neck.

The larynx and cricoid cartilage with the intervening cricothyroid

membrane are identified. From the cricoid, moving caudally, the

tracheal rings are identified. The tracheostomy should ideally pass

between the second and third tracheal rings, although a space one

higher or lower may be employed. Placing the airway higher, next tothe cricoid, can cause tracheal erosion and long-term problems.
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Technique: Seldinger method

Local anaesthetic with adrenaline is infiltrated subcutaneously, and a 1 cm incision made

horizontally with a scalpel. Keeping in the midline at all times, the introducer needle and

syringe are advanced, at 45 degrees to the skin, until air is aspirated from the trachea.

The guide wire is passed through the needle, then the small dilator (green) is passed. This is

then removed and the white introducer passed into the trachea. The guidewire is removed.

Now only the white introducer is left in the trachea. Over this the tracheal dilator(s) (blue)

are passed in order, gradually dilating the incision to accommodate the appropriately sized

tracheostomy tube. Plenty of lubricating jelly is applied to each dilator, and they are passed

down the tract with a twisting motion. Only moderate downward force is applied. If the dilator

does not pass easily, return to the previous smaller dilator and ensure that it passes freely

and easily. Often, it is the skin that impedes progress, and the incision has to be slightly

widened with the scalpel. The portex kit consists of a one-step dilatation.

Each size of tracheostomy tube has a corresponding dilator size (see the manufacturers'

instructions), and this should pass freely and easily into the trachea before attempting to

insert the tracheostomy tube. Once the tracheostomy will easily accept the final dilator, the

tracheostomy tube (cuff already checked) is loaded onto the dilator one size lower. The

tracheal tube is wathdrawn, under direct vision, into the larynx, and the tracheostomy tube is

passed over the introducer into the trachea. Once again, undue force should not be

necessary. Use plenty of jelly and, if required, return to the previous dilator.

The use of the tracheal dilator instruments is rarely necessary, and may be hazardous.

However, if the introducer is inadvertently pulled out of the trachea, or some other mishap

occurs, they may be useful in relocating the tract for replacement.

With the tracheostomy tube in place, the tracheal tube is removed and the ventilator isconnected to the tracheostomy. The chest is auscultated for adequate ventilation and the

ventilator checked for appropriate tidal volumes and airway pressures. The tube is secured

with tapes or ties.

References

1. Elective percutaneous dilatational tracheostomy. A new simple bedside procedure;preliminary report. Ciaglia P, Firsching R, Syniec C.Chest 1985; 87: 715-19.

2. Percutaneous endoscopic tracheostomy. Paul A et al.Ann Thorac Surg 1989; 47: 314-15.

3. Percutaneous dilatational tracheostomy. Results and long-term follow-up [seecomments]. Ciaglia P, Graniero KD.Chest 1992; 101: 464-7.
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Anatomy of Tracheostomy