James Montgomery, DVMSeptember 21, 2009

8 yo MC Yorkshire Terrier Chronic cough Collapsing trachea

– acute episode night prior to presentation at NCSU

Fluoroscopy

Link to movie

Two types• Dorsoventral – often associated with a

pendulous redundant dorsal tracheal membrane

• Lateral – very unusual (rarely occurs spontaneously)

Obstruction of the trachea• Intrinsic weakness of the tracheal cartilage

rings• Laxity of the dorsal tracheal membrane

With rare exception, toy and miniature breed dogs• Yorkshire terrier: 1/3 – 2/3 of all reported

cases• Chihuahuas• Pomeranians• Toy poodles• Shih Tzus• Lhasa apsos

Usually middle-aged and older dogs No sex predisposition

Coughing is a sign consistently present • Chronic “honking” cough

Cough elicited with tracheal pressure at thoracic inlet (by palpation or pulling on leash), excitement, drinking water or eating food

Acute episodes: Respiratory distress +/- cyanosis

Physical exam usually normal otherwise

Frequently affects the entire trachea, though cervical or thoracic tracheal may be involved alone

Inspiration:• Negative intrapleural pressures expand the

intrathoracic airway lumen, while luminal pressure at the cervical level becomes negative cervical trachea collapses on inspiration

Expiration:• Intrapleural pressure increases, becoming

positive – once intrapleural pressure exceeds the airway opening pressure, the thoracic trachea collapses

Vicious cycle: 1.Collapsed trachea initiates coughing2.Coughing and enforced respiration

increase intrathoracic pressure causing opposing epithelial linings to come into contact mucosal injury

3.Chronic epithelial injury causes inflammation and epithelial desquamation which disrupts mucociliary clearance

4. With chronicity, mucous gland hyperplasia can occur causing increased respiratory secretion

5. Secretions accumulate in the trachea, as mucociliary clearance has been disrupted further aggravates cough and tracheal collapse

A progressive disorder

Medical Management

Surgical• Chondrotomy• Plication of the dorsal tracheal membrane• Extraluminal prostheses• Endotracheal Stents

Treatment of choice initially

Important to identify and manage any triggering event break the pathologic vicious cycle• Allergies• Obesity

Deleterious effects on cardiopulmonary system, decreased lung expansion, and increased breathing effort

• Treatment of existing infectious or inflammatory lung disease

• Management of congestive heart failure

Antitussives• Hydrocodone and butorphanol• Reduce chronic irritation or damage to the

tracheal epithelium Antisecretory drugs

• Atropine• Decrease excessive accumulation of mucus in

the respiratory tract Bronchodilators

• Methylxanthine• Theoretically reduce spasm of the smaller

airways, reducing intrathoracic pressures and decreases tendency of larger airways to collapse

Primary goal is to restore normal tracheal diameter without disrupting the mucociliary flow.

Tracheal Ring Chondrotomy and Plication of the dorsal tracheal membrane• Lead to reduction in tracheal diameter –

techniques out of favor

Extraluminal prostheses• C-shaped polypropylene• Improvement of clinical signs in 75-85% of

patients• Mainly limited to cervical trachea• Difficult procedure• Invasive• Severe complications:

Laryngeal paralysis, tracheal necrosis (decreased tracheal blood flow), loosening or failure of the implant

Intraluminal stents• Promising technique – still

looking for optimal stent material

• Fluoroscopic guidance• Self-expanding biliary

Wallstents most common Uncovered, metallic stent –

epithelialization permanent• Relatively easy to deploy –

orotracheal route• Less invasive• Shorter recovery time• Expensive - $1500

Complications: stent migration, granulation tissue, tracheal perforation

Ettinger SJ, Dantrowitz B. Diseases of the Trachea. In Ettinger SJ, Feldman EC, eds. Textbook of Veterinary Internal Medicine, 6th ed (St. Louis, MO: Elsevier Saunders, 2005) pp. 1217-32.

Moritz A, et al. Management of advanced tracheal collapse in dogs using intraluminal self-expanding biliary Wallstents. Journal of Veterinary Internal Medicine 18 (2004) pp. 31-42.

Sun F, et al. Endotracheal stenting therapy in dogs with tracheal collapse. The Veterinary Journal 175 (2008) pp. 186-93.