The Trachea Flashcards
Number of trachea layers?
What are they?
4: mucosa, submucosa, cartilaginous-muscle layer and adventitia
What is the thickest structure in the trachea, how doe sit run?
Hyaline cartilage is thickest ventrally and then tapers along the curved arms.
What happens to Hyaline cartilage with age?
Calcifies
What is different in the dorsal trachea?
Dorsally there is no cartilage, instead there is a dorsal tracheal ligament
Wat 3 things is the dorsal tracheal ligament composed of?
mucosa, connective tissue, and smooth muscle
What breeds are predisposed to hypoplastic trachea? (2)
French bulldog
english bulldog
What is seen anatomically with a hypoplastic trachea?
Rings are overlapping with minimal tracheal membrane.
Trachea:
A) What is it lined by?
B) How dos it lubricate? (2)
A) pseudostratified ciliated columnar epithelium
B) lubricated by goblet cells and lubricating glands
The cilia sweep bronchial mucus towards the larynx at a rate of ?
12 mm per minute.
What allows contraction and expansion of the diameter?
Pleated mucosa
What sized tube for tracheostomy in dogs?
Size 5 and 6 tubes
What sized tube for tracheostomy in cats?
3 or 4
Emergency tracheostomy:
How to?
Cut down onto the needle or go straight down with an 11 blade - stay ventral. Split the rings to access the trachea.
The incision can also be made vertically through the rings but the risk of stenosis is greatly increased.
Emergency tracheostomy; What can be used to locate the trachea if it is swollen?
Needle
Cuffed tracheostomy is only used when?
ventilation is required
Stylets or cannulas decrease the lumen of the tracheostomy tube, thus what effect on airway resistance
increasing
What causes stenosis during tracheostomy?
Transecting rings (not splitting)
The presence of the tracheostomy tube results in what damage? (3)
loss of cilia,
inflammation,
mucosal erosion
Effect of tracheostomy on arytenoid abduction.
Reduces
What surgery is tracheostomy useful in? When do you place?
intraoral surgery
- Ideally placed as an elective surgery after oral intubation.
When to remove tracheostomy? (2)
- obstruction gone
- the animal can manage with occlusion or removal of tube
What tracheostomy tube is used?
simple silicon tubes are used, with no inner cannulas or cuffs (unless ventilating). Shiley™ tubes work well.
First removing the trach tube; what to do?
Obseverve patient
When do trach tubes commonly need replacing?
night if the obstruction is nasopharyngeal or nasal and titrate the use of the tube down over a couple of days.
How to heal tracheostomy?
2ry intention
Benefits of 2ry intention healing for trach tubes? (2)
additional airflow for a few days
prevent subcutaneous emphysema.
What proportion of the tracheal lumen should be occupied by the tracheostomy tube?
50-60%
Why is the trach tube smaller than trachea diameter? (2)
- breathing around the tube if it occludes
- reduce damage to the laryngeal mucosa.
Tracheostomy tubes: How to position
- Extend the head over a sandbag.
Tracheostomy tubes:
Where is the incision?
Which muscles do we go through? (2)
- ventral midline incision over trachea from caudal larynx to 7th or 8th tracheal ring and continue through subcutaneous tissues
platysma and sphincter coli muscles.
Tracheostomy tubes:
Separate the two ? muscles along the midline to expose ventral trachea.
sternohyoid
Tracheostomy tubes:
In thick neck dogs such as bulldogs, consider bluntly dissecting dorsal to the trachea and placing what through the strap muscles to bring them into apposition dorsal to the trachea. This suture pushes the trachea superficially closer to the skin, enabling tube changes.
a mattress suture
Tracheostomy tubes:
Where is the trachea incised? How large is incision?
Make circumferential tracheal incision ventrally between cartilage rings 3 and 4 or 5 and 6. Incision should be around 50% of the tracheal circumference
Tracheostomy tubes:
Care to avoid what? Where are they?
taking care to avoid recurrent laryngeal nerves dorsolaterally.
Tracheostomy tubes:
A) Where are stay sutures place?
B) Using what?
C) How long are they there for?
A) around the cartilage ring above and below the tracheal incision
B) Place 2 or 3 metric monofilament, non-absorbable (e.g. polypropylene) stay sutures
C) Duration of management, used to open stoma during replacement. UNTiL REMOVED
Labels should be placed on trach tube stay sutures; saying what?
Head and tail end!
After trachea incision, how is the trach tube placed?
Withdraw the ET tube so the tip is just cranial to the tracheostomy incision and insert the tracheostomy tube through the tracheal stoma and into the trachea below the ET tube. Switch anaesthetic circuit to the trach tube and remove ET tube from mouth.
Place a what between the tracheostomy tube and the subcutaneous tissue/trachea
sterile swab
How to tie trach tube in?
Use nylon tape to tie the tube in place around patient’s neck.
How to care for a trach tube? (3)
Intensive care – the patient needs continuous monitoring
Use a humidifier/nebulisation (steam) for 10-15 minutes every 3-4 hours
Remove and clean every 8-24 hours depending on discharge being produced.
ABx with trach tube?
Within 24 hours the tube will be colonized with oropharyngeal flora. Avoid antibiotics whilst the tube is in unless indicated for i.e., aspiration pneumonia.
Indications for a Permanent Tracheostomy? (3)
laryngeal collapse,
permanent upper airway obstruction
damage to proximal trachea.
What is the longterm consequence of a permanent tracheostomy?
Alter vocalisation
What is the incision for a Permanent Tracheostomy
Make a ventral cervical incision and approach to the trachea.
Permanent Tracheostomy:
Blunt dissection allows elevation of trachea to the skin over which area?
Ring 3-8
Permanent Tracheostomy:
muscles are sutured together dorsally to the trachea, pushing it more superficially?
sternohyoideus
Permanent Tracheostomy:
After the incision, what is the next step?
The ventral aspect of 3-5 rings are removed, leaving the mucosa intact if possible. An oval shape of skin is resected, the subcutaneous tissue is sutured to the tracheal fascia and cartilage and the mucosa sutured to the skin with simple appositional sutures (interrupted or continuous).
Permanent Tracheostomy:
How big to make teh stoma?
50% larger than anticipated
Permanent Tracheostomy: what additional steps in brachy dogs?
Excise any skin folds that could obscure the stoma. This usually means removing large crescents
Primary collapsing trachea:
A) Where is affected?
B) Breed size?
C) What age?
D) When is collapse?
A) cervical trachea and can be fixed or dynamic.
B) larger dogs
C) young age.
D) inspiration if dynamic.
Secondary collapsing trachea:
A) Exacerbated by? (2)
B) Affects which part?
C) Collapse seen when?
D) What breed?
A) Other disease such as chronic bronchial disease or heart disease.
B) dynamic in nature and affecting the thoracic trachea.
C) expiration.
D) smaller breed
Tracheal collapse is perpetuated by?
Chronic inflammation of the dorsal tracheal membrane
Inflammation of the mucosa can lead to (2)
squamous metaplasia
polypoid changes
Tracheal collapse: the normal ciliary function is replaced by what as the main tracheobronchial clearing mechanism.
a cough
It is critical that concurrent conditions are identified for appropriate management of tracheal collapse since secondary factors such as ? (2) will exacerbate the condition as will co-existing medical conditions.
obesity
cigarette smoke
Is there a role of bacteria in tracheal collapse?
One study that investigated the role of bacterial infection in tracheal collapse (TC) looked at tracheobronchial brush samples. Whilst significant numbers (83%) of dogs with TC had positive bacterial cultures (mostly Pseudomonas spp.) there was no cytological evidence of inflammation or infection so the role of bacteria in this condition was unconfirmed
Pathophysiologt of tracheal collapse?
Cartilage rings degenerate and become hypocellular with decreased content of hyaline cartilage and increased fibrocartilage. There are reduced amounts of glycoprotein and glycosaminoglycans, notably chondroitin sulphate and calcium which leads to a loss of rigidity.
Breed for tracheal collapse? (4)
Toy Yorkie,
Pomeranian,
Pug,
Maltese Terrier
Age for tracheal collapse?
All ages are affected but most presented when middle aged (7 years)
What % of cats have tracheal collapse?
0.5
Clinical signs of tracheal collapse (5)
Mild productive cough to harsh honking cough: the honking cough is produced when the flaccid tracheal membrane resonates during forced expiration of air
Can be a clicking noise in cervical trachea
Exercise intolerance
Overweight (often)
Other signs of respiratory or cardiac disease
How can tracheal collapse lead to right sided cardiac hypertrophy?
Increased respiratory expiratory pressures can lead to increased pulmonary vascular resistance and right-sided cardiac hypertrophy.
How t diagnose tracheal collapse? (7)
CE
Tracheal palpation
Tracheal compression test
Laryngeal examination
Fluoroscopy
Radiographic examination
Endoscopy
How to have a dynamic view of collapse?
Fluoroscopy
What xrays are taken for tracheal collapse?
Inspiratory and expiratory extubated views.
Define grade I tracheal collapse
< 25% trachealis mm impinging on tracheal lumen
Define grade II tracheal collapse
50% decrease lumen diameter
Define grade III tracheal collapse
75% decrease in lumen diameter
Define grade IV tracheal collapse
Total tracheal collapse trachealis muscle lies on tracheal floor
Medical Tx of tracheal collapse (6)
Remove noxious inhaled stimuli from environment
Advise weight loss where appropriate
Consider antitussives (e.g. butorphanol)
Consider bronchodilators
Prescribe antibiotics where necessary:
Consider anti-inflammatory doses of corticosteroids
Most common isolated from tracheal collapse (4)
Staphylococcus spp., Pasteurella spp., Pseudomonas spp. and E. coli
What drugs improve mucociliary clearance? (1 e.g. (2))
Methylxanthines such as aminophylline or theophylline
When should surgery be considered from tracheal collapse? (2)
progressive disease in spite of good medical management,
when the collapse is Grade III or IV
Before resorting to tracheal surgery correct what?
other surgical airway problems such as BOAS, elongated soft palate, laryngeal paralysis.
Surgical options for tracheal collapse (2)
External prosthetic support
Internal stents
Sx has best prognosis at what age?
<6 yr
External prosthetic support:
A) What is used?
B) Where is this most useful? (2)
C) Where is this not useful? (2)
A) Split plastic rings of 5-8 mm thickness are placed around the trachea to provide support.
B) cervical trachea and access at the thoracic inlet
C) intra-thoracic or bronchial collapse.
External prosthetic support:
A) How are rings placed to maintain flexibility ?
B) placed with as little disruption as possible to the fascial pedicles to avoid damaging? (2)
A) The rings are placed 2-3 ring apart
B) recurrent laryngeal nerve or vascular supply.
External prosthetic support complications?
Tracheal necrosis
Laryngeal paralysis
Persistent cough that may last for 3-4 weeks
Why may External prosthetic support lead to laryngeal paralysis? (3)
- Pre existing
- Manipulation of the recurrent laryngeal nerve
- Scarring/firbosis weeks later affecting nerve
What can be done at surgery to avoid laryngeal paralysis with External prosthetic support ?
left arytenoid lateralisation
Internal prosthetic support:
Initially Palmaz stents were tried but movement occurred; there were improved success rates with (2)
stainless steel wall stents
nitinol stents.
Nitinol:
A) An alloy of?
B) What 2 beneficial properties does it have?
A) Nickel and titanium
B) Thermal shape memory + Elasticity
How are Internal prosthetic support placed? (2)
fluoroscopically
under endoscopic visualisation
When are Internal prosthetic support used?
thoracic
bronchial collapse
Intraluminal surgical intervention is essentially a salvage procedure and intra-luminal stenting is best reserved for dogs that (2)
not good candidates for extra-luminal prosthesis
have failed medical treatment (i.e., end-stage
Internal prosthetic support pros? (3)
short anaesthetic/short post op convalescence
minimally invasive deployment,
rapid restoration of lumen
Post op coughing after Internal prosthetic support is common why?
stent interferes with mucocilliary clearance and predisposes to lower respiratory tract infection
Internal prosthetic support
Unfortunately, due to their location, they are also prone to severe bending forces which cause stents to be prone to kinking and fracture leading to
granuloma formation.
Internal prosthetic support:
These stents are impossible to remove once they have been deployed. It is possible to carry out repairs by
telescoping
Tracheal trauma can occur secondary to (4)
blunt or penetrating traumatic incident,
foreign body,
traumatic avulsion injury
mucosal damage by traumatic endotracheal intubation
What are the most common clinical signs of tracheal trauma? (4)
Subcutaneous emphysema
Pneumomediastinum
Pneumothorax
Dyspnoea
When is conservative tx appropriate for tracheal trauma?
small tracheal lacerations which will seal without surgical intervention.
How to choose tracheal trauma treatment options? (2)
respiratory rate and effort
progression of any pneumothorax.
How to approach trachea for direct appositional repair
A ventral approach to the neck can be used to approach the trachea
What can be used to strengthen any surgical repair to the trachea.
Muscle flaps comprising of the sternohyoideus or sternothyroideus
When should tracheal anastomosis be considered?
If there is mucosal loss of more than 35% of the tracheal diameter then resection of the damaged tracheal section
What stents have been used in the trachea (2)
How long can stents be left in?
Montgomery T-tube tracheal stent or Fingercot stents
Leave for months
Tracheal transection/avulsion is usually reported in what size dog or cats?
Small dog
What typically causes Tracheal transection/avulsion?
hyperextension
The trachea ruptures proximal to the carina and the peritracheal tissues can form a
pseudotrachea
Tracheal transection/avulsion treatment?
resection and anastomosis
With Tracheal transection/avulsion; which part of the trachea may stenose?
Distal
What causes internal tracheal injury?
High pressure, low volume cuffed endotracheal tubes
Tip of ET tubes
Pathophysioology of ischaemic necrosis of the internal trachea?
Local collapse of the mucosal vessels and nutrient vessels
Clinical signs of progressive dyspnoea will occur when there is a what% decrease in luminal diameter.
60-70
What cuff pressure/volume is preferred?
low pressure, high volume cuffs
