Tracheal collapse: old disease; newer treatment options (Proceedings)

Tracheal stent placement is a novel treatment option for dogs presenting with tracheal collapse refractory to traditional medical management and for those in which the nature and location of the collapse make them poor candidates for prosthetic ring placement. The goal of this handout is to provide the reader with a brief overview of tracheal collapse, treatment options, selection criteria for stent candidates, an overview of the technique, and the expected outcome.

Diagnosis & Medical Management of Dogs with Tracheal Collapse:

Despite the rapidly growing popularity of tracheal stents for the management of tracheal collapse, medical management remains the cornerstone of therapy. Only those refractory to medical management and those in which medical management is compromising quality of life are generally considered as candidates for tracheal stent placement or other palliative surgical options. The majority of dogs with tracheal collapse will present electively for evaluation of cough or a restricted or stridorous breathing pattern noted chronically by the owners. A tentative diagnosis of tracheal collapse is made based on signalment, clinical signs, and physical examination findings. Definitive diagnosis of tracheal collapse is based on various imaging modalities including thoracic radiography (3 view) to help rule out concurrent diseases as well as fluoroscopy and /or tracheobronchoscopy.

Fluoroscopy is the author's preferred method for dynamic evaluation of tracheal collapse. The patient is allowed to spontaneously breathe, and cough while being imaged fluoroscopically. Using this technique, the extent of the tracheal collapse and the presence of main stem bronchial (MSB) collapse can be evaluated. This information is valuable when determining optimal definitive treatment measures (surgery for prosthetic ring placement vs. tracheal stent placement).

Tracheobronchoscopy performed under general anesthesia is a preferred technique for some to evaluate the extent of the tracheal collapse and to grade its severity while concurrently identifying the presence of MSB collapse.

It is important to ascertain the presence of MSB collapse because the presence of MSB collapse significantly impacts response to treatment (and persistence of cough). Finally, the author always evaluates the larynx for evidence of dysfunction, structural abnormalities (collapse), or the presence of a mass.

Medical management is always attempted for the management of dogs with tracheal collapse prior to other interventions (surgery or tracheal stent placement). Anti-inflammatory doses of corticosteroids have a significant place in both the acute and chronic management of dogs with tracheal collapse. Injectable forms of corticosteroids equivalent to prednisone (0.5-1mg/Kg/day) may be administered soon after presentation in an effort decrease tracheal inflammation. Corticosteroid therapy should be weaned beginning one week after treatment begins to a level that is low enough to optimally control clinical signs. To the authors' knowledge, the efficacy of corticosteroid administration in the acute management of tracheal collapse has not been objectively investigated.

Initiating therapy with hydrocodone (0.22mg/Kg PO Q6hrs PRN) is effective for cough suppression. Cough is a significant complaint for many dogs with tracheal collapse, especially those with intrathoracic and main stem bronchial collapse. Finally, comorbid conditions should be treated concurrently.

Palliative Treatments for Dogs with Tracheal Collapse:

When medical management cannot adequately control clinical signs of tracheal collapse such that quality of life is compromised, palliative interventions (surgery for prosthetic ring placement or tracheal stent placement) must be considered. It is critical for the client to accept that these interventions are palliative and will not cure the problem. Instead, the goal of these procedures is an improvement in clinical signs and less reliance on medical therapies.

If the tracheal collapse is only in the cervical region and at the level of the thoracic inlet, surgical placement of prosthetic tracheal rings is a reasonable consideration. It should be noted however, that the success of this procedure is very operator dependent. Intraluminal placement of a self-expanding metallic stent is a rapid, relatively simple procedure that can restore the patency of the tracheal lumen without the need for open surgical intervention.

Tracheal Stent Case Selection Criteria:

Tracheal stent placement is an option, but is not considered optimal by the author for all dogs with tracheal collapse. Younger to middle-aged dogs with cervical collapse and collapse at the thoracic inlet in need of elective intervention may be best treated through placement of prosthetic rings. The reason for this is (at this time) the increased durability of prosthetic rings over time. Tracheal stent fracture and subsequent mechanical failure has been a recognized complication of tracheal stent placement whereas failure of prosthetic rings would be considered extremely rare.

Tracheal stents are most often placed in dogs with intrathoracic collapse or those with diffuse tracheal collapse. In addition, the author will often recommend tracheal stent placement over prosthetic rings in extremely small patients, in those that are extremely old, those with many comorbidities, and those that present intubated in the emergency setting and cannot be extubated due to airway obstruction. Finally, some clients will elect a minimally invasive treatment option over open surgical intervention (prosthetic rings) even if surgical intervention is perceived to be the superior treatment option.

Client Expectations for Dogs Undergoing Tracheal Stent Placement:

It is critical that owners of dogs with tracheal collapse undergoing tracheal stent placement recognize that the tracheal stent procedure is palliative in nature and will not CURE their dog. We expect 70-90% improvement (1 month post-procedure) in clinical signs in dogs without concurrent MSB collapse and approximately 50% improvement in clinical signs in dogs with MSB collapse. Clients must recognize that medical management will be ongoing, but that the procedure will often result in a decrease in dependence on medical management. The presence of MSB collapse in dogs with intrathoracic collapse is challenging because it is often difficult to determine if the cause of expiratory cough is a result of the MSB collapse, intrathoracic tracheal collapse, or a combination of both. It is also unknown how much of the cough and expiratory dyspnea is resulting from the tracheal component of the disease and how much is coming from the MSB component. Complications (please see below) should also be discussed at length prior to the procedure.

Tracheal Stent Placement Technique:

Briefly, the location of the tracheal collapse is known based on fluoroscopy performed when the patient was awake. The length of the collapse is measured precisely during the procedure being sure to account for the effects of magnification. During a positive pressure breath (20mmHg), the tracheal width is measured both cervically and intrathoracically. Based on the needed length and width of the trachea, an appropriately sized tracheal stent is selected. The stent is usually oversized (10-20%) for width to ensure appropriate apposition to the inner wall of the trachea. Tracheal stent sizing is challenging because of the physical and deployment properties of the woven stents commonly used for these procedures.

Recovery and Discharge from the Hospital:

Most dogs that undergo tracheal stent placement are hospitalized for one night after the procedure. Medical management is ongoing and will include a cough suppressant (hydrocodone 0.22mg/Kg PO Q6-12hrs), prednisone (0.2-0.5mg/Kg Q12hrs x 14 days then gradual weaning to lowest possible dose), and an antibiotic. A dry cough is expected for approximately one month. In addition, if MSB collapse is present, coughing related to MSB collapse will persist. Persistent coughing should be treated aggressively. Persistent coughing may apply considerable forces to the stent and may be involved in the pathogenesis of stent fracture. Recheck exam including radiography is usually performed 2-4wks after placement and then every 6 months thereafter to evaluate the stent for fracture.

Complications of Tracheal Stent Placement:

Like many other medical interventions, tracheal stent placement is not without complications. Acute complications are generally avoidable through careful attention to detail when making measurements and meticulous stent deployment. If the stent diameter is undersized in relation to the trachea, stent migration will be a problem resulting in persistent cough and possible stent expulsion. An undersized stent that has migrated should be removed. Malpositioning of the stent is another acute complication. The stent may be deployed into the carina or MSB resulting in persistent coughing and possible "caging-off" of the lobar bronchi. The stent may also be accidentally deployed in the larynx or the endotracheal tube necessitating removal.

Stent fracture is the most commonly recognized long-term complication of tracheal stent placement. Numerous factors may contribute to stent fracture and research/development efforts by stent manufacturers are always ongoing to optimize design to minimize this complication. It is the authors opinion that persistent cough may contribute to stent fracture. Inflammatory tissue formation (especially at the ends of the stent) has been a documented problem in some dogs undergoing stent placement.

Conclusions:

Tracheal stent placement is a minimally invasive, technically feasible palliative treatment modality for dogs with tracheal collapse. The procedure offers a treatment option for dogs with tracheal collapse that are not amenable to medical management.

*Significant portions of these proceedings have been previously published at various veterinary continuing education meetings.

Further Reading:

1. Moritz A, Schneider M, et al. Management of advanced tracheal collapse in dogs using intraluminal self-expanding biliary wallstents. Journal of Veterinary Internal Medicine 2004; 18: 31-42.