Collapsing Trachea

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Collapsing Trachea

• Mark Bohling, DVM
• Diplomate, American College of Veterinary
  Surgeons
• Assistant Professor of SurgeryUniversity of
  TennesseeCollege of Veterinary Medicine

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What is Tracheal Collapse?

• Normal airflow dynamics in respiration
• Inspiration
• Expansion of chest by muscles of respiration
• Pressure gradient - chest negative
• Effect on the air conduit
• Thorax - expansion
• Neck - compression
• Expiration
• Reverse effects

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History of Collapsing Trachea in Veterinary
Medicine

• Described as early as 1960
• Review of early treatments
• Single plastic tube
• Ventral chondrotomy
• Modified ventral chondrotomy
• Dorsal membrane plication

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Tracheal Collapse in Other Species

• Tracheal collapse in human beings
• History
• Dates to 1930s
• Similarities
• Softening of tracheal cartilage
• Lateral collapse (same as dorsoventral in dogs)
• Differences
• Classification
• Primary vs secondary collapse
• Pediatric vs adult collapse

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Tracheal Collapse in Other Species

• Tracheal collapse in large animals
• Horses
• Congenital
• Secondary to laryngeal paralysis
• Cattle
• Acquired neonatal
• Tracheal collapse in birds
• Bordetella avium in turkeys

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Tracheal Collapse in the Dog

• Miniature breeds
• Middle aged to older
• Other risk factors
• More pronounced in obese individuals

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Levels of Collapse
Normal
G1
G2
G3
G4
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Levels of Collapse
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Clinical Signs

• Chronic, dry nonproductive cough (honking)
• Intermittent dyspnea (worsens with excitement)
• Cyanosis syncope in severe cases
• Inspiratory/ expiratory dyspnea
• Prone to heat stroke

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Clinical Signs
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Pathophysiology

• Disease causes the trachea rings to weaken
• Dorsal ligament and trachealis muscle weaken and
  stretch
• Trachea changes from oval tube to a flattened
  conduit

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Etiology

• Congenital
• Nutritional tracheomalacia
• Obesity
• Bacterial infection
• Neurologic
• Chronic airway disease
• Idiopathic who knows why

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Diagnosis

• Tracheal palpation
• Radiographs (inspiratory / expiratory )
• Fluoroscopy
• Tracheoscopy

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Radiographs
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Tracheoscopy
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Medical Management

• Cough suppression(Hydrocodone, butorphanol)
• Bronchial dilators(Aminophylline, terbutaline)
• Sedation(Acepromazine)
• Weight loss

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Medical Management

• Help control symptoms
• Can not be cured
• Disease usually progressive

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Surgical Correction

• External stenting with plastic rings

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Before
After
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Surgical Correction

• External spiral stent

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External Stent Complications

• Collapse between rings

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External Stent Complications

• Damage to recurrent laryngeal nerve

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External Stent Complications

• Interruption of tracheal bloodsupply

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Internal Stenting

• What is a stent?
• History of stenting
• History of tracheal stenting
• Modern stents and stent materials
• Stents in veterinary medicine

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Ultraflex Stent

• Radiopaque, self-deployed
• 4 - 8 cm length, 10 - 20mm diameter
• Made of nitinol (nickel-titanium alloy)
• Proximal or distal deployment
• Single strand, open loop knitted design
  (flexible, contourable)
• Boston Scientific/ Microvasive.

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Ultraflex Stent
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Ultraflex Stents
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SmartStent

• Nitinol tube
• Laser cut
• No overlapping wires
• Less breakage in human vascular applications
• Cordis Endovascular

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Infiniti Stent

• Also nitinol
• Single woven wire
• Only stent produced exclusively for vet use
• Claims as yet unproven

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Stent Placement

• Stent deployed under fluoroscopic guidance
• Target 5mm cranial to bifurcation
• Placement checked with tracheoscopy

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Stent in Place
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Radiographs
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Postoperative Care

• Perioperative antibiotics
• Corticosteroids for 7 days
• Sedation
• Cough suppression
• 24 hours oxygen if needed
• Humidification

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6 Month Post Implant
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Stent Results

• The little girl with the curl syndrome
• Good outcomes
• Immediate improvement
• Breathing near normal
• Mild chronic cough
• And the not-so-good outcomes

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Stent Complications

• Stent fracture
• Granulation in stent
• Tracheal exudate
• Additional collapse at ends of stent

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Fractured Stent
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Fractured Stent
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Stent Fracture

• Originally thought to be due to bending stresses
• All brands/types of nitinol stents can fracture -
  there is NO unbreakable stent
• At this time, removal is best option - BUT - not
  for the fainthearted!

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Granulation Tissue
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Tracheal Mucus
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Collapsed at Ends
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Stent plus Rings
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Stent Advantages

• Preserves tracheal blood supply
• Preserves recurrent laryngeal nerve
• Continuous tracheal support
• Easy deployment
• Multiple, sequential deployment

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Rings vs. Stents

• Cost to client (stent more expensive)
• Stents are easier and quicker
• Complication rate similar
• Neither cure, only control symptoms
• Stent placement requires expensive equipment
• Rings require surgical expertise
• Lack of proper size stent

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A typical case with tracheal rings

• Day 1 Preop workup (bloodwork, radiographs,
  tracheoscopy)
• Day 2 Surgery
• Postop recovery in ICU
• Day 3 Still in ICU
• Day 4 Discharged from hospital
• Home monitoring continue medical therapy 2 4
  weeks
• Recheck time variable, depends on outcome
• Long term outcome usually good, but

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A typical case with tracheal stent

• Day 1 Workup as for rings. Order stent from
  supplier
• Day 2 Stent arrives (usually). Stent is placed
  in a 30 minute procedure and patient recovers in
  ICU
• Day 3-4 Recovery in ICU
• Day 5 Discharge from hospital
• Home care for 2-4 weeks
• Re-check tracheoscopy at one month to check if
  stent is embedded

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Miss Piggy - Stent disaster case 1

• Signalment Miss Piggy
• 6 year old spayed female Yorkie
• Body weight 13 lbs (BCS 8/9!!)
• Grade III/VI heart murmur
• History
• Coughing for past 2 years, getting worse past yr
• Presented to emergency clinic Saturday night
• Unable to breathe, cyanotic
• Oxygen dependent

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Miss Piggy

• Presentation at UT
• Still oxygen dependent
• Tracheoscopy findings
• Cervical - Grade 3 entire length
• Thoracic - Grade 3-4 entire length
• Left main bronchus Grade 2-3
• Plan stent entire trachea
• Poor anesthetic risk
• Guarded prognosis given

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Miss Piggy

• Stent placement
• Thoracic stent 1 cm cranial to carina
• 5mm overlap at thoracic inlet
• Cervical stent 1 cm caudal to cricoid

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Miss Piggy

• Postop first 24 hours
• Doing well in oxygen
• Next day
• Trial period out of oxygen - - cough and cyanosis
• Back to oxygen and medical mgmt
• Antitussives
• Bronchodilators

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Miss Piggy

• 3rd postop day
• Brief trial out of oxygen - - same result
• Still looks good in oxygen
• 4th postop day
• 4am cant get comfortable
• 7am - 7pm awake all day
• 9pm lung sounds getting harsh
• 11pm crackles ausculted

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Miss Piggy

• 5th day.
• Early am hours - No response to bronchodilators
  or diuretics
• Patient very tired, has not slept in 24 hours
• 9am - respiratory failure

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Stent disaster 2 - Tuffy

• Signalment
• 4 year old male castrated Yorkie
• BW 8 lbs, BCS 6/9
• History
• Started at 2 years old
• Now coughs at slightest exertion
• Cyanotic with mild exercise

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Tuffy

• Tracheoscopy
• Cervical collapse - grade 3
• Thoracic collapse - also grade 3
• Bronchi both open
• Plan
• Stent entire trachea

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Tuffy

• Immediate postop
• Doing well!
• 3 weeks later
• gagging noticed
• Recheck at UT
• BOTH stents fractured
• Tracheal lumen open but small
• Lots of exudate

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What next?

• Immediate plan
• Stabilize his condition
• Antibiotics
• Some antitussives
• Definitive plan
• Stent removal
• Re-stent over the broken ones

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Tuffy the outcome

• Survived the procedure!
• Immediate improvement in breathing
• Went home doing well, but some cough
• Continued to improve
• Still coughs some
• Overall quality of life better than before
• Cost to owner 5K total, lots of gray hair!

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Future Needs

• Immediate needs
• Improved surgical treatment options
• Less breakable stents
• Improved rings - can we go intrathoracic?
• Improved medical management options
• Cough suppression with less sedation
• Tracheal cartilage - can malacia be arrested?

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Future Needs

• Long-term needs
• Greater understanding of the etiology of this
  process
• What is happening at the cellular and molecular
  level?
• Identification of molecular/genetic marker(s)
• Creation of a breed registry for this disease
• Apparent genetic cause
• Can we breed it out?

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Special thanks to

• Dr DJ Krahwinkel
• Sue Schwarten
• Danielle Browning
• UT photo and media services
• Linda Hicks and Mr T

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Thank you any questions?