Description

The cartilage rings of the trachea (windpipe) are shaped like the

letter C, lying on its back. A small membrane covers the top of the

ring. In some dogs, the tracheal cartilages lose their rigidity, and the

membrane stretches. The rings collapse, the windpipe flattens, and

mild to severe obstruction of the airway develops. Tracheal collapse

occurs primarily in small-breed dogs, such as the miniature

poodle, Yorkshire terrier, Pomeranian, and Chihuahua.

This is an acquired, not congenital, disease. Some dogs can

start showing signs of tracheal collapse at a relatively young

age, but it is usually a disease of older dogs. Tracheal collapse

can occur in the neck region, within the chest, or in both

locations.

Causes

The cause is not well understood, but proposed theories include

genetic factors, nutritional influences, neurologic problems, and

degeneration of the tracheal cartilages.

Clinical Signs

Abnormal respiratory noises, difficulty breathing, cyanosis (blue

gums and tongue from lack of oxygen), exercise intolerance, and

possibly fainting may occur. An intermittent “goose-honking”

cough that has a sudden onset is a common sign. Applying pressure

to the trachea often induces a cough.

Diagnostic Tests

Flattened cartilages may be detected when your veterinarian palpates

(feels) the neck area. Chest x-rays demonstrate tracheal collapse

in only 60% of affected patients, but they help rule out heart

and other lung diseases as a cause of the signs. Video x-rays (fluoroscopy)

show the movement of the trachea throughout the entire

respiratory cycle and detect some cases of tracheal collapse that

are missed on plain x-rays. Fluoroscopy is available at some referral

institutions and veterinary hospitals.

The definitive diagnostic method is endoscopy (tracheobronchoscopy),

which involves passage of a fiberoptic viewing scope

into the trachea. This procedure demonstrates the degree and exact

location of the collapse. Endoscopy also allows collection of samples

for bacterial culture, as many affected dogs have a secondary

infection. During the procedure, laryngeal function may also

be evaluated, because 25-30% of dogs with tracheal collapse also

have laryngeal paralysis. Tracheobronchoscopy has some inherent

risks and is not performed in all patients with suspected tracheal

collapse.

Treatment Options

Medical therapy usually is effective in dogs with mild collapse

and signs. It often includes cough suppressants, drugs to dilate

the bronchial tree, and antibiotics for secondary infections. Antiinflammatory

steroid medications (tablets or inhaler) may be used

on a short-term basis to reduce inflammation of the lining of the

trachea. Some dogs benefit from use of tranquilizers during periods

of excitement that could result in severe respiratory distress.

Dogs with additional types of upper airway disease, such as

laryngeal paralysis, may benefit from surgical correction of these

disorders. Avoidance of high environmental temperatures and situations

that induce excitement helps many of these patients. Obese

dogs are placed on a weight-reduction diet.

Because of the inherent risks and potential complications

related to tracheal surgery, most of these cases are managed medically

whenever possible. Surgery is reserved for those dogs with

severe collapse and little or no response to medical therapy or for

those that become refractory to medications. If the collapse is at the

very end of the trachea, where the bronchi of the lungs begin, it is

usually considered unsuitable for any type of surgery.

The purpose of tracheal surgery is to support the tracheal cartilages

and expand the tracheal diameter. Support of the tracheal

cartilages can be accomplished by using prosthetic tracheal rings

that are applied on the external surface of the windpipe. This type

of surgery is usually limited to those dogs with collapse in the neck

region. Placement of stents inside the trachea can be used to correct

collapse of the trachea within the chest or the neck. The stents

are usually inserted using endoscopy or fluoroscopy.

Follow-up Care

Close monitoring is required in the immediate postoperative

period, so the dog may remain hospitalized. Because the placement

of external tracheal rings is difficult and tedious, laryngeal

paralysis may develop that requires another surgery (to treat the

paralysis). Chronic coughing is associated with either surgery,

but especially with stent placement. The coughing can often be

managed with concurrent medical therapy.

Prognosis

Medical therapy can provide relief, in many cases for the life of

the patient. When surgery is successful, it often reduces the clinical

signs and improves the quality of the dog’s life. The duration

of the benefit from surgery is variable, because tracheal collapse is

a progressive disease.