Surgery STAT: Tracheal collapse: rings or stents?

Surgery STAT: Tracheal collapse: rings or stents?

Aug 01, 2008

EDITOR'S NOTE: SurgerySTAT is a collaborative column between the American College of Veterinary Surgeons (ACVS) and DVM Newsmagazine. In September, Shawn Mattson, DVM, DVSc, BSc will discuss "Treating Subchondral Bone Cysts in the Fetlock Joint." Dr. Mattson is an ACVS board-certified surgeon who practices at Moore and Company Veterinary Services, a full-service equine hospital in Calgary, Alberta, Canada. Dr. Mattson, previously at the Ontario Veterinary College in Guelph, Ontario, has published scientific articles in the American Journal of Veterinary Research and Veterinary Surgery related to research on orthopedic infections in horses.

Tracheal collapse, or tracheal chondromalacia, is a progressive, degenerative condition of the trachea that can ultimately result in severe respiratory compromise.

Different underlying causes are recognized that can occur alone or in conjunction with one another and include: (1) Hyaline cartilage rings that lose integrity and can no longer support the tracheal lumen or (2) weakening of the trachealis muscle that contributes to the loss of tracheal lumen during different phases of respiration.

The resulting clinical syndrome typically manifests as a "goose honk" cough with varying degrees of dyspnea and is most commonly identified in toy breed dogs. Non-surgical management techniques can be useful to palliate clinical signs for years, but more aggressive treatment often is required for those animals that eventually fail these more conservative approaches.

Photo 1: Lateral radiographs demonstrating dynamic tracheal collapse during inspiration (above) and expiration (below), suggesting the weakness of static radiographs for determining the extent of tracheal collapse.
Aggressive medical therapy always is performed before any more invasive techniques, because these treatments are basically salvage procedures associated with considerable risk to the patient. Other concurrent conditions, such as underlying pulmonary, cardiac, laryngeal/upper airway and endocrine diseases should be managed before invasive tracheal procedures are considered.

Photo 2a: Polypropylene rings used for external tracheal support.
If conservative therapy fails to provide a reasonable quality of life for the patient, surgical rings and tracheal stents are the more commonly used surgical treatments available. There is a tendency to choose one or the other of these two options; however, both should have important roles in the management of tracheal collapse.

I consider the location of the collapse to be one of the most important factors in deciding which technique to recommend. Routine radiography can be useful for the diagnosis of concurrent conditions and the presence of tracheal collapse, but more dynamic studies obtained during coughing are needed to fully identify the extent of the collapse.

During inspiration, the subatmos-pheric airway pressures generated in the cervical trachea lead to collapse in that location, whereas during exhalation the increased intrathoracic pressures lead to collapse of the intra-thoracic trachea. This often can be appreciated upon careful evaluation of the respiratory pattern during physical examination as well.

Photo 2b: Partially deployed self-expanding nitinol stent used for intraluminal tracheal stenting.
Individual static radiographs may fail to document fully the extent of the collapse, as demonstrated in Photo 1 with two subsequent radiographs of the same dog during two different phases of respiration (cervical tracheal collapse during inspiration and intra-thoracic tracheal collapse during expiration).