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
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.
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 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.
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.
Photo 2a: Polypropylene rings used for external tracheal support.
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.
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).
Photo 2b: Partially deployed self-expanding nitinol stent used for intraluminal tracheal stenting.