Ch 102 - Trachea and Bronchi Flashcards
What makes up the trachea?
- Hyaline cartilage rings
- Trachealis muscle
- Annular ligaments
How many tracheal rings do dogs have?
35 (can range up to 46)
How many cartilage rings are present in the right and left mainstem bronchi?
- Left = 3
- Right = 1
What is the major blood supply to the trachea?
- Segmental blood supply from cranial and caudal thyroid arteries
- At the carina, blood supply shifts primarily to bronchoesophageal arteries
List the functions of the trachea
- Conduit for gases to and from the lungs
- Warming and humidification to air
- Mucociliary escalator
What is a normal mucociliary flow rate in a dog?
10-15mm/min - speed and efficiency are hindered by increasing particle size and mucous viscosity
What nerve supplies smooth muscle control to the trachea?
Vagus
- Right branch assumed to be dominant in dogs
What is the expected tracheal diameter to thoracic inlet in normal dogs? Brachycephalics? English Bulldogs?
- Normal: 0.2 +/- 0.03
- Brachy: 0.16 +/- 0.03
- Eng. Bulldog: 0.13 +/- 0.38
What are the options for a temporary tracheostomy?
- Cuffed or uncuffed tube
- Single or double lumen
- Silicon tracheal stoma stent
What muscle needs to be seperated on the approach to the cervical trachea?
Sternohyoideus
What is the maximum length of the transverse temp trach incision?
What is the maximum recommended diameter of the trach tube?
- Maximum incision 50%
- Maximum tube size 75% of tracheal diameter
What is the recommended time for application of a suction device?
- No more than 10-12 seconds at a time and then releases
- Uninterrupted suctioning can lead to severe atelectasis and hypoxia
What options are there to provide adequate humidification for a temp trach patient?
- 0.2ml/kg sterile saline through trach tube every 1-4hr
- Nebulisation
How can you assess the suitability of trach tube removal?
Provided that air can flow around the trach tube, occlude with occlusive dressing for 15-20min while CLOSELY monitoring patient
What are the reported complications with a temp trach tube?
Acute complications in up to 50%
- Plugging of the tube 18-25%
- Inadvertent tube removal
- SQ emphysema
- Pneumomediastinum
- Pneumothorax
- Infection
- Resp distress
Cats: 87% complications, 40% life threatening
- 91% with benign disease discharged from hospital
What is the most significant long term complications of temporary tracheostomy?
Stenosis. Associated with larger tubes and inflated cuffs
- Can occur at stoma or level of cuff or tip of tube
- Average loss of 18-24.7% luminal area
- High-vol, low pressure cuffs have reduced incidence of this complication
What is the overall complication rate and survival for temp tracheostomies in dogs and cats?
Dogs
- Overall complications 86%
- Successfully managed in 81%
- However, only 60% survived to discharge
Cats:
- 43% survived to discharge
List the three options for a temp trach incision
- Transverse
- Tracheal flap
- Vertical
What is the recommended size of the tracheal incision for a permanent tracheostomy?
- Ventral half of 3-4 tracheal rings
Why should a permanent tracheostomy not be performed in the distal trachea?
- Higher mortality rates (57%) when the tracheostomy is performed below the 12th tracheal ring
What happens to the tracheal epithelium after a tracheostomy?
Undergoes squamous metaplasia causing excessive mucous production for the first 4-6 weeks
List reported complications of permanent tracheostomy
- Mucous plugs
- Aspiration pneumonia
- Requiring revision surgery
- Acute death following discharge 26%
- Stenosis up to 60%
- MST cats 20.5 - 42 days
- Major complications in 10 of 20 dogs, MST 328d
If pre-existing collapse, should be reinforced with extraluminal rings
How does a tracheotomy/bronchotomy incision heal?
- Epithelialise within 2-8hr
- 48hr - transitional epithelium
- From 96hr - transformation into ciliated and goblet cells can begin
How long does it lake a 1x1cm defect of the trachea to heal?
15-20 days
What degree of tension produced tracheal stenosis?
- 750g of tension will invariably produce stenosis
- 1500g causes circumferential strictures
Stenosis of 50-75% is required to cause clinical signs
List some methods for reducing tension at a tracheal anastomosis site
- Tension-relieveing sutures placed several rings proximal and distal (can negate pressure over 2000g)
- Fixed ventroflexion of the neck
- Release of the annular ligament wth preservation of the mucosa
How does suture closure of the trachea compare to native tracheal strength?
- Continuous suture closure nearly as strong as native trachea immediately
- By 1-2 weeks, suture repair is stronger then native trachea, regardless of interrupted vs continuous
How does age effect the strength of the trachea?
- Adult trachea can withstand forces of 1700g at the anastomosis site which correspons to removal of 50-58% of the tracheal length
- Juvenile trachea can only withstand 60% of the force of the adult trachea, and therefore can only resect 20-25% of the trachea (higher water content with less collagen)
What complication is associated with nonabsorbable suture material?
Granuloma formation and stricture
List anastomotic options for the trachea
Split cartilage technique
- Less DV luminal stenosis
- More precise alignment
- May be stronger as heals with fibrocartilage
Annular ligament cartilage technique
What is the recommended approach to the intra-thoracic trachea?
Right-sided 3rd-5th IC thoracotomy
Azygous vein ligated and transected
Vagus, phrenic and recurrent laryngeal nerve protected
What options are there for augmentation/reconstruction of a tracheal anastomosis?
- Omentum
- Hyaluronic acid
- Fibrin tissue adhesive
- Auricular cartilage struts
What is the effect on mucociliary clearance after a resection and anastomosis?
Reduced atleast 3 fold, reestablished over the following month
What is the effect of tesion on tracheal anastomosis healing?
- Cartialge seperation beginning laterally and spreading ventrally
- Any gaps will heal by second intention and increase the degree of stricture
- Severity of stenosis appears to correlate with amount of traches resected
What % of cats with tracheal rupture have SQ emphysema?
100%
What is the recommended treatment for tracheal rupture?
- Medical management (cage rest, O2, sedatives). SQ emphysema take approx 2 weeks to resolve
- Surgery if worsening dyspnoea, lack of response to O2, worsening emphysema
Where have all reported tracheal ruptures occured?
At the junction of the tracheal ring and the trachealis muscle
Where does tracheal avulsion tend to occur?
What is the likely cause?
- Occurs at the weakest part of the trachea 1-4cm proximal to bifurcation
- Caused by blunt trauma while in hyperextension of the neck
What is usually seen on imaging for tracheal avulsion?
- Pneumomediastinum
- Pseudoairway (more chronic)
What is the accuracy of radiographs in the diagnosis for a tracheal FB?
66%
Absence of finding in 14.8%
List primary tumours of the trachea
- Osteochondroma
- Osteosarcoma
- Chondroma
- Chondrosarcoma
- Ecchondroma
- Leiomyoma
- etc
What is the treatment of choice for tracheal neoplasia?
What is the exception?
- Surgical resection and anastomosis
- NOT for lymphoma
List some benign masses of the trachea
- Granulomatous
- Abberant Cuterebra larvae
- Nodular amyloidosis
- Broncholithiasis
- Tracheal intussusception
What lesion is often seen in association with bronchoesophageal fistulae?
Oesophageal diverticula
What are the reported histological changes of the tracheal rings with tracheal collapse?
- Hypocellular with reduction in glycoprotein and glycosaminoglycans leading to decreased water retention
- Increased complicance and decreased rigidity
- Decreased chondroitin sulphate and calcium may allow replacement of hyaline cartilage with collagen and fibrocartilage
List DDx for tracheal masses
Neoplastic:
- Osteochondroma, OSA, Chondroma, chondrosarcoma, ecchondroma, leiomyoma, etc
Benign
- Granulomatous disease
- Aberrant curerebra larvae
- Haemorrhage
- Nodular amyloidosis
- Brocholithiasis
- Tracheal intussusception
What condition is often assoc with bronchoesopageal fistula?
Oesophageal diverticulum (potentially predisposing to FB)
What breeds are predisposed to tracheal collapse?
What % may be affected by 6mo?
- Yorkies, min poodles, pom, chihuahua, pug
- As many as 25%
Which imaging technique gives the most valuable diagnostic information regarding tracheal collapse?
Tracheoscopy
What is the grading system for tracheal collapse?
- Grade I - 25% collapse (laxity of dorsal tracheal membrane)
- Grade II: 50% collapse
- Grade III - 75% collapse
- Grade IV - 100% collapse
What is the rate of severe, life-threatening complications with intra/extraluminal tracheal stenting for tracheal collapse?
10% - only recommended if they have failed medical therapy
What are the main complications of extraluminal polypropylene rings?
- Laryngeal paralysis 11-30%
- Tracheal necrosis
- Pneumothorax
- Collapse beyond rings
- Migration
- 91% survival to discharge, 88% survived over 6m
- 65% no longer required medical management
What is the recommended sizing for intraluminal stents?
- Tracheal diameter measured on radigraphs with cuffed ET tube at larynx and positive-pressure ventilation at 20cmH2O
- Stend diameter should exceed widest diameter by 10-20%
- Should span entire trachea from 1cm caudal to cricoid to 1cm cranial to carina
List potential complications of intraluminal stents
- Stent fracture (persistant coughing)
- Stent migration (inaccurate measurements)
- Inflammatory tissue (motion, Ix, coughing)
.
.
. - Immediate improvement 95.8%
- 83-89% improve for over 1yr
- MST significantly shorter than extraluminal (365vs1460d) but dogs were significantly older…
- 43% complication rate (vs 42% extraluminal)
What % of dogs with tracheal collapse will also have bronchial collapse?
71-83%
What breed is overrespresented for congenital lobar emphysema?
What is it?
What lobe is most commonly effected
- Pekingese
- Congenital bronchial cartilage abnormalities or absense allowing lungs to inflate but then become trapped
- Right middle lung lobe most common
What is Kartagener syndrome?
- Situs invertus
- Chronic rhinosinusitis
- Bronchiectasia
What conditions are commonly seen in dogs with ciliary dyskinesia?
- Bronchopneumonia
- Hydrocephalus
- Thickening of typanum due to obstruction of ciliated auditory tube
- Situs invertus
What are the reported complications with a temp trach tube?
Acute complications in up to 50%
- Plugging of the tube 18-25%
- Inadvertent tube removal
- SQ emphysema
- Pneumomediastinum
- Pneumothorax
- Infection
- Resp distress
Overall complications in up to 86%
- successfully managed in 81%
- Only 60% survived to discharfe
Cats: 87% complications, 40% life threatening
- 91% with benign disease discharged from hospital
