Chapter 102 Trachea and Bronchi Flashcards
Label the diagram
How many terminal bronchioles are dogs estimated to have?
17,000 - 36,000
What type of cartilage are tracheal rings composed of?
Tracheal rings composed of hyaline cartilage
What is the name of dorsal muscle connecting traceal rings (N.B. inserts to external surface of tracheal rings)
Trachealis muscle
Approximately how many tracheal rings are there (and upper range)
Approx 35 tracheal rings (up to 46 reported)
What si the name of the tissue between tracheal rings?
Annular ligament
How many cartilage rings is the left mainstem bronchus typically made up of? And the right?
Typically 3 rings in left mainstem bronchus, only 1 in right.
How are bronchioles distinguised from smaller bronchi?
Smaller bronchi contain overlapping cartilage plates (rather than rings); diasppearance of plates marks transition to bronchiole.
List the layers of the trachea:
- Mucosa
- Submucosa
- Fibrocartilaginous layer
- Adventitia (in cervical trachea), serosa (in thoracic trachea).
where along thelength of the trachea is the cartilage the thinnest and the luminal diameter smallest?
At thoracic inlet
What type of epithelium lines the trachea?
Ciliated, pseudostratified, columnar epithelium
Aside from goblet cells, there are other mucus secreting glands in the trachea.
- What are they named?
- How do they differ from goblet cells?
- What is the pproximate density of these cells in canine trachea?
- What are they named? Tubuloalveolar mucus glands
- How do they differ from goblet cells? Produce equivalent mucous of 40 goblet cells
- What is the pproximate density of these cells in canine trachea? 1 opening/mm
During progression down the bronchial tree, how does ‘cell population’ vary?
Tubuloalveolar glands disappear first, then goblet cells, then ciliated cells.
Where does the trachea receive its segmental blood supply from?
Cranial and caudal thyroid arteries. Branches travel towards midline where they extensively anastomose
Where do the mainstem bronchi/bronchioles receive blood supply from?
Broncho-oesophageal arteries.
What is the venous drainage of the trachea/bronchi?
Thyroid vein, jugular vein, broncho-oesophageal veins
List 4 lymph nodes that drain trachea/bronchi:
- Cranial mediastinal
- Medial retropharyngeal
- Deep cervical
- Tracheobronchial
Which nerves supply the trachea/bronchi?
Is there a dominant side (in dogs at least)?
Vagus/recurrent laryngeal
Right dominant side. (L stimulation –> only 28% response compared with R stimulation)
List 3 functions of trachea
- Conduit fo rair passage
- Warms and humidifies air
- Mucociliary clearance
What is the typical mucociliary clearance rate in dogs?
1 - 1.5 cm/min
List two physiological changes that occur with trachealis m contraction
- Increased airflow velocity
- Increased rigidity
- Creates mucosal inversion ‘furrow’ along which mucus collected and expelled
What is the normal ratio of tracheal:thoracic inlet diameter in:
Normal dogs:
Brachy dogs:
English Bulldogs:
Normal dogs: 0.2
Brachy dogs: 0.16
English Bulldogs: 0.13
List 3 radiographic findings of URT obstruction.
And 3 of lower RT obstruction
URT obstruction:
- Tracheal narrowing distal to obstruction
- Tall, domed diaphragm
- Under-aerated lungs
- (Poss pulmonary oedema)
Lower RT obstruction:
- Flattened diaphragm
- Over-inflated lungs
- –> prominent pulmonary vasculature
*
What is the advantage of fluoro over rads for evaluatio of trachea?
What is the advantage of CT over rads?
List an advantage of tracheobronchoscopy:
- Fluoro allows dynamic assessment (increased intrathoracic pressure (e.g. during cough) can exacerbate collapse)
- CT results in less under-estimation of dimensions (CT validated as method for diagnosing tracheal hypoplasia, collapse, stenosis in non-anaesthetised dogs and cats = “virtual endoscopy”!)
- Tracheobronchoscopy allows grading of collapse and evaluation of bronchial tree (?presence of bronchomalacia), collection of BAL.
what proportion of BAL fluid must be retirieved for sample to be considered representative?
How can yield be maximised?
>33% of infusate to be considered representative
Use of surgical suction pump (max -37 mm Hg, pulsatile) vs manual aspiration
List 3 contraindications for temporary trach tube
- Collapse distal to tracheostomy
- Obstruction distal to tracheostomy
- Tracheal stent in place
What are the recommendation re transverse tracheostomy inscision?
And tracheostomy tube size?
Other tube considerations?
3rd, 4th, 5th ring, no more then 50% of circumference.
Outer tube diameter <75% of tracheal diameter
Cannulated vs non cannulated. If cuffed hig volume low pressure cuff!
List 5 aspects of post-op trach tube care
- Nebulise/instill 0.2ml/kg sterile saline q4h
- Replace/clean cannula of tube bid or suction airway (pre-and post oxygenate, attach to ECG as bradycardia (vagal response) can occur, atelectasis and hypoxia too, max 10-12 seconds at a time)
- Banage surrounding area
- Abx ointment around stoma and clean
- If cuffed, deflate q4h.
What are the to potential points of tracheal stenosis following temporary tracheostomy?
Incision or cuff/tube tip site.
What proportion of dogs with temoprary tracheostomy tubes are reported to survive to discharge?
And cats?
60% of dogs with temp. trach survived to discharge
43% of cats with temp. trach survived to discharge
List 5 potential short term complication sof temporary tracheostomy tube placement, and 2 longer term.
Short term complications:
- Tube blockage
- Inadvertent tube removal
- SC emphysema/pneumomediastinum/pneumothorax
- Coughing/gagging
- Infection
- Respiratory distress
Longer term complications
- Tracheal stenosis
- Tracheal necrosis
In dogs undergoing temporary tracheostoomy tube placement, what is the average percentage loss of luminal size ?
What degree of stenosis is necessary before clinical signs become evident?
On average, luminal size reduced by 18-25%
50 - 75% stenosis necessary before clinical signs are evident.
How does placement of temorary silicone tracheal stoma stent compare to ususal ttt placement (Trinterud)?
More invasive to place, no dogs suffered life-threatening complications
Briefly list steps of permanent tracheostomy
- Ventral midline approach, mattress sutures in sternohyoideus to appose them odrsal to trachea.
- Excision of window 9max 50% circumference) from 3-4 tracheal rings, leaving mucosa intact.
- Incise rotated “H” shape into mucosa to allow it flap dorsally and laterally.
- Suture mucosa to skin using 3/0 or 4/0 monofilament absorbable (approx 2mm apart)
From tobias pic;
A, Mattress sutures are used to appose the sternohyoideus muscles dorsal to the trachea. A segment of cartilage is removed, and the mucosa is incised (dashed line).
B, Interrupted sutures are used to attach the mucosa to the skin at the corners of the stoma. A simple continuous pattern is then used to meticulously attach the tracheal mucosa to the skin.
What did Dahm and Paniello report re stoma loacation in permanent tracheostomy?
Higher mortality rate (57%) when stoma paced caudal to 12th ring (“likely excessive tracheal kinking” ?skin fold)
What occurs to the mucosa following creating of permanent tracheostomy?
Mucosa undergoes squamous metaplasia –> excessive mucou sproduction for up to 4-6 weeks.
What was the most common complication of permanent tracheostomy in cats? What was cat MST?
What were the two most common complications in dogs? And MST in dogs?
Cats:
Mucus plugs –> death (25% of cats)
MST cats 20-42d
Dogs:
Aspiration pneumonia and need for revision sx (stenosis)
MST dogs 328d (also 25% acute death after discharge - assumed airway obstruction)
How can permanent tracheostomy be re-inforced of tracheal collapse is present?
Extratracheal rings (extra-luminal polypropylene rings)
List 5 environmental modification following permanent tracheostomy
- Weight management
- No swimming
- No aerosols/scented candles/dust
- Harness, no neck lead
- Hair clipped
In a tracheotomy/bronchotomy, how long does it take:
For epithelialisation to begin?
For transitional epithelium to rise?
For transformation into goblet cells and ciliated cells?
In a tracheotomy/bronchotomy, how long does it take:
For epithelialisation to begin? 2-8 hours
For transitional epithelium to rise? 2 days
For transformation into goblet cells and ciliated cells? 4 days
What anaestehtic consideration are necessary for tracheal R+A?
- Et tube long enough to bypass incision or sterile ET tube and circuit (for tranincisional intubation)
- TIVA rather than inhalation anaesthesia.
How much adult canine trachea can be resected?
And in puppies? Why?
50% in adult dogs
20 - 25% in puppies (because higher water content and lower collagen content in cartilage –> more fragile)
List 3 tension relieveing techniques following tracheal R+A
- Tension relieving sutures (placed several rings proximal and distal to anastomosis)
- Fixed neck ventroflexion
- Annular ligament release (with preservation of mucosa)
In a growing rabbit model, what was the difference between simple cont vs simple interrupted (absorbable) sutures following trcheal R+A.
Significantly more tracheal growth with simple interrupted absorbable sutures (i.e. alos less growth with non-absorbable, in any pattern)
What did Behrend and Klempnaurer find re electrocautery and tracheal healing?
Slowed mucosal healing i.e. recommedn against electrocautery
List two techniques for tracheal anastomosis
What was the difference in outcom between the two?
“Split cartilage/ring” technique
“Annular ligament cartilage” technique
Split cartilage –> less DV stenosis
What is the approach for intra-thoracic trachea?
What else can be done to maximise exposure?
R 3-5th ICT
Ligate and divide azygous vein
List 6 key steps for tracheal R+A
- Vagus, phrenic and recurrent laryngeal nerves identified and preserved
- R+A + transincisional ventilation if necessary
- Pre-place stay sutures in dorsal tracheal membrane (3/0 - 4/0 Monofilament, 2-3mm apart)
- Pre-place around exit of ET tube.
- +- tension relieving sutures
- Leak test (PEEP to 20 cm H20)
- (Omentum or hyaluronic acid to augment (neither reported clinically)
What is post-op stenosis following tracheal R+A correlated with?
Tension/lenght of trachea resected
How can tracheal stenosis be managed?
Balloon/bougienage, usually need repeat R+A
In cases of tracheal tear, when is surgery indicated (3 scenarios)
- Worsening Sc emphysema
- Worsenign dyspnoea
- Lack of response to oxygen
Where is the typical location of tracheal avulsion?
What is the typical radiographic finding?
1 - 4 cm cranial to carina
Pseudo-airway (dilated lumen bounded by soft tissue)
List 2 probable reasons tracheobronchial FBs are rare
Imminent death so not investigated
Experimentally 20/22 FB coughed up within 2 weeks
HOw accurate is radiography for determining location of tracheobronchial FB?
False negative rate on rads?
66% accurate
15% false negative
List 5 techniques for tracheobronchial Fb removal
What percentage require surgical removal?
- Hold patient upside down + shake
- Tracheobronchoscopy
- Fluoroscopic guidance
- Foley/Fogarty/balloon wedge catheter
- Surgery (tracheotomy)
13-20% require sx removal following unsuccessful tracheobronchoscopic retireval.
List 10 primary tumours of trachea
- Osetosarcoma
- Osteochondroma
- Chondroma
- Chondrosarcoma
- Fibroma
- Fibrosarcoma
- Leiomyoma
- Rhabdomyosarcoma
- MCT
- extramedullary plamsa cell tumour
- Adenocarcinoma
- Lymphoma
- SCC
- Basal cell carcinoma
List 3 organisms that may cause inflammatory tracheal lesions
- Mycobacterium
- Spirocerca
- Onchocerca
Can also get nodular/diffuse amyloidosis, broncholithiasis, tracheal intussusception
How can congenital vs aquired bronhcooesophageal fistulae be distinguished from one another?
What si the most common cause of aquired fistulae?
Histo. Congenital fistulae have squamous epithelium, aquired have granulation tissue
Oesophageal FB
How can an oesophageal fistula be diagosed?
Contrast oesophagram (avoid iodonated - risk of oedema)
Tracheobronchoscopy/oesophagoscopy
CT
What are the histo findings in dogs with tracheal collapse?
Cartilage is hypocellular with a reduction in glycoproteins and GAGs, that is associated with decreased water retention within the matrix.
Decreased chondroitin sulphate and calciummay also allow for replacement if hyaline cartilage with collagen and fibrocartilage.
Breifly diecribe pathophysiology of vicious cycle in tracheal collapse
Cough + inflammation
–> loss of normal epithelium
–> fibrinous membrane epithelium
–> squamous metaplasia of epithelium + hyperplasia of subepithelial glands
–> reduced cilliated cells and increasingly viscous mucous secretions
–> cough becomes primary clearance mechanism
List 4 external factors hypothesised to exacerbate traheal collapse
- Obesity
- Environmental allergens
- Cigarette smoke
- Kennel cough
What is the sensitivity and specificity of radiographs for diagnosis of tracheal collapse?
Sensitivity 60%
Specificity 75%
For diagnosis of tracheal collapse, how did fluoro differ from rads and tracheobronchoscopy?
Fluoro deteced significantly more sites of collapse durign induction of cough
How is tracheal collapse graded (n.b. can only use this when assessed bronchoscopically)
Tangner and Hobson described a three-dimensional, endoscopic grading system still in use today. Grades I to IV represent 25%, 50%, 75%, and 100% collapse
List 5 factors of chronic medical management of tracheal collapse
- Corticosteroids (pred 0.5 - 1 mg/kg/day) for short periods - investigate with BAL etc if requires extended course)
- Weight management
- Environmental modification
- Harness walk/controlled exercise
- Nebulization/Humidification
- (Bronchodilators)
- (Short course abx if infection suspected)
What are the surgical indications for tracheal collapse?
Garde 2-4 collapse + failed medical management
N.B.Check for lar par, laryngeal collapse and long palate on induction.
List 3 broad techniques for surgical management of tracheal collapse
- Extraluminal prosthetic tracheal rings (polypropylene)
- Extraluminal spiral prostehesis
- Intraluminal stent
List a purported advantage of extraluminal spiral prosthesis. And a disadvantage
Advantage:
- Uniform support
Disadvantage
- Thoracotomy necessary for intrathoracic placement
List a key step in the placement of extraluminal prosthetic tracheal rings
Place ring axial to recurrent laryngeal and tracheal vessels
Ensure placement of sutures dorsally in trachealis muscle
What is the survival to discharge following extraluminal prosthetic tracheal rings?
List 5 potential complications
91% survival to discharge
Complications:
- Laryngeal paralysis (11 - 30 %)
- Tracheal necrosis (authors recommend skeletonising only right pedicle (as more space between recurrent laryngeal and trachea, than left pedicle. Or make tunnel only where ring is passed.)
- Implant migration
- Infection
- Collapse beyond rings
- Tearing of trachealis membrane
- Pneumomediastinum/pneumothorax (suspect tear from traction @ thoracic inlet - be clipped for chest drain just in case)
What is nitinol made up of?
Nickel + titanium alloy.
How do intraluminal stents resits migration?
Radial stress against tracheal wall
List 3 advantages of intraluminal stent vs extraluminal prosthetic tracheal rings
Non-invasively placed
Shorter GA
Can span cervical and ontra-thoracic collapse
What are the specific recommendations re stent selection (4 properties)
Nitinol
Wound
Reconstrainable
Foreshortening
Why are laser cut stents not recommended?
High rate of fracture
How specifically should rads be obtained for tracheal stent planning?
How is stent size chosen (diameter and length)?
What radiographic landmarks are used to determine location of cricoid and carina?
Rads
- Calibrated oesophageal probe
- ET cuff at larynx and inflate to 20 cm H2O
- Get expiratory rads too
Stent size:
- Length: Ideally, from 1 cm caudal to cricoid to 1cm cranial to carina (consult manufacturer guide re expected foreshortening). At least spanning collapsed area
- Diameter: 10-20% larger than maximal rad diameter
Landmarks:
- Cricoid: Beneath C3-C4 disc space
- Carina: Level with 4th rib
List 4 post-op meds following intraluminal stent
- Anti-tussives
- Sedative
- Corticosteroids (tapering anti-inflammatory)
- Antibiotics (2 weeks)
Re-assess stent regularly with rads.
What is the rate if major complications in extraluminal prosthetic rings vs intraluminal stent?
Extra-luminal rings: 42%
Intra-luminal stent: 43%
List 5 possible complications of intraluminal stenting
- Stent fracture (initailly try aggressive medical management, otherwise stent inside or remove piecemeal with scope vs tracheotomy/R+A)
- Stent migration
- Inflammatory tissue in-growth
- Tracheitis (60%)
- Tracheal rupture
- Collapse beyond stent
- Persistent cough
How does CT measurement of tracheal diameter compare to rads?
Rads underestimate size by approx 1mm.
What percetage of dogs with tracheal collapse have bronchial collapse?
71-83%
Stenting of mainstem bronchus reported in a dog. Concern re progressive collapse of smaller bronchi is rational efor recommending against bronchial stenting. and bronchial stent will ‘cage off’ smaller bronchi
What breed get congenital lobar emphysema?
Which lobe is most commonly affected?
Pekingese, WHWT, JRT, Shih Tzu, Chow Chow
R midde lobe
What are the three types of bronchiectasis and which is most common in dogs?
Breeds?
Cylindrical, saccular and cystic.
Cylindrical most common in dogs.
Spaniels, Westies, Huskies
If single lobe involved excision can be curative but usually result of chronic underlying condition
Which 3 findings make up Kartagener syndrome?
- Situs invesus
- Chronic rhinosinusitis
- Bronchiectasis
Define ciliar dyskinesia.
How is ciliary dyskinesia diagnosed?
What histological abnormalities may be present?
Ciliary diskinesia = dysfunctional or non-functional cilia
Dx: electron microscopy or generationof cilia in culture
Histo: basal foot processes, microtubule doublets, dynein arms.
