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Tracheal Collapse
Overview of the condition
Tracheal collapse is a chronic, progressive disease of the trachea, or windpipe. The trachea is a flexible tube and, similar to a vacuum cleaner hose, it has small rings of cartilage that help keep the airway open when the dog is breathing, moving, or coughing. The rings of cartilage are C-shaped, with the open part of the C facing upward. Between the two ends of the C is a long band of tissue- the dorsal membrane- that runs the length of the airway. In some dogs, the C-shaped cartilage becomes weak and begins to flatten out. Initially it becomes U shaped but, as the dorsal membrane stretches, the cartilage rings get flatter and flatter until the trachea collapses (Figure 1). The collapse can extend all the way into the bronchi- the tubes that feed air into the lungs, resulting in severe airway compromise in the animal.
Figure 1. Diagram of tracheal collapse. Tracheal collapse is graded mild (Grade 1 = 25% collapse) to severe (Grade 4 =100% collapse). The trachea in dogs most often collapses at the thoracic inlet (green arrows) where the trachea bends to enter the chest.
Signs/Clinical presentation
Initially dogs may present with a harsh dry cough that sounds like a goose honking. Coughing may occur when the dog is picked up or if someone pulls on its collar, since either may put pressure on the airway. As the disease progresses, the dogs may develop exercise intolerance or even turn blue with excitement. The strain of breathing may cause secondary heart disease. Some dogs may also have laryngeal paralysis along with tracheal collapse; the cartilages at the entrance to the windpipe will not open properly and the dogs will develop a wheezy noise when they breathe inward.
Risk Factors
Small breed dogs are most commonly affected with the disease, particularly Yorkshire terriers, Pomeranians, poodles, and Chihuahuas. Affected dogs are often middle aged or older, though it can be seen in some young dogs as well. Dogs that are overweight or that live in household with smokers may be more at risk or at least more likely to show clinical signs.
Diagnostic tests
Chest x-rays (Figure 2, 3) may help with the diagnosis in some animals, and are useful for ruling out other conditions and looking at the size of the heart. Tracheal collapse is not always visible on regular x-rays, however. Fluoroscopy- a moving x-ray- will allow the veterinarian to check the condition of the dog's trachea when it is breathing in and out (Figure 4). This is important since the size of the trachea can change with the phase of respiration. Endoscopy- viewing the inside of the trachea with a fiberoptic camera - provides the best detail of the inside of the airway (Figure 5) and allows the veterinarian to take fluid samples for culture and microscopic analysis. Veterinarians may also recommend an echocardiogram- an ultrasound of the heart- to evaluate its function, and blood work to check for any other health problems.
Figure 2. This chest x-ray corresponds to the diagram in Figure 1 and shows a tracheal collapse of varying severity in a Yorkshire terrier. In the lower the neck, the trachea narrows 50-75% (red arrows). As the trachea passes through the thoracic inlet, it narrows 100% (green arrows). Within the chest, the collapse appears to be mild (blue arrows). Endoscopy would be needed to determine whether there is collapse of this area.
Figure 3. This dog has severe (Grade 4) collapse of its entire trachea (green arrows) and its bronchi (red arrows).
Figure 4. This fluoroscopy provides a series of x-rays of the dog in Figure 3 as it breathes. The airway collapses and then widens with air movement out and into the trachea.
Figure 4b
Figure 4c
Figure 4d
Figure 5. Endoscopic views show a normal trachea (Figure 5a.) near the bronchi (smaller airways); a trachea with Grade 2 moderate collapse (Figure 5b); and a trachea with Grade 4 severe collapse (Figure 5c).
Figure 5b
Figure 5c
Differential diagnoses
Any disease that affects the upper or lower airway can be confused with tracheal collapse, including a long soft palate, laryngeal paralysis, infection in the trachea or lungs, foreign object in the airway, heart failure, or tumors.
Treatment Options
Medical management includes weight loss, cough suppressants, antispasmodics or bronchodilators to reduce airway spasms, and sedation to reduce coughing and anxiety. Some dogs may require heavy doses of sedation to break the coughing cycle, since coughing will irritate the airway and lead to more coughing. Additionally dogs should be kept away from smoke and other environmental pollution (coughing may be even stimulated by smoke or other irritants brought in on clothing and hair). Dogs with infections are treated with antibiotics.
Medical management may work for up to 70% of dogs, particularly those that have mild collapse. Some animals do not respond to medical management, however, and require surgical or interventional treatment. Collapse of the trachea in the neck or thoracic inlet- the front part of the chest where the trachea bends- is treated by surgical placement of plastic rings (Figure 6, 7) or spirals around the outside of the trachea. If the collapse is deep within the chest, it can sometimes be corrected by placing a stent- a spring like device- inside of the airway to hold the trachea open (Figure 8). Most dogs that receive stents will require ring placement in the neck or thoracic inlet region as well.
Figure 6. Tracheal rings come in different sizes (Figure 6a). The rings (Figure 6b- green arrows) are placed around the trachea and sutured in place. When the placement is complete (Figure 6c), the airway is held open by the sutured rings.
Figure 6b
Figure 6c
Figure 7. Before the rings are placed, this trachea (Figure 7a) was collapsed 50%. After the rings were placed (Figure 7b), the inside of the airway looks much rounder. Some of the sutures that hold the rings in place are visible (green arrows).
Figure 7b
Figure 8. Stents (Figure 8a) come in different sizes and materials. When the stent is first placed in the airway, the wires are visible (Figure 8b). After several weeks to months, the stent becomes buried under the tracheal lining (Figure 8c).
Figure 8b
Figure 8c
When to seek referral
Tracheal collapse is a very serious disease and surgical treatment is fraught with complications. Specialized diagnostic tests such as fluoroscopy and endoscopy are often not available at general veterinary practices. An ACVS Veterinary Surgeon who has experience with the surgery procedure should perform surgical placement of rings. An ACVS Veterinary Surgeon or a specialist in interventional radiology or internal medicine usually performs placement of stents within the trachea. Any veterinary practice that offers these procedures should have a fully staffed intensive care unit and oxygen available for postoperative care.
Potential complications of surgery
Placement of rings around the trachea requires delicate dissection of the blood vessels to the trachea and the nerves to the larynx (the upper airway). Because of irritation from the surgery or the rings, dogs can develop coughing, bleeding, airway damage, or even paralysis of the larynx. Dogs that have a paralyzed larynx may require emergency surgery to tie open the airway or to temporarily allow breathing through a hole in the neck ("tracheostomy"), and some may die immediately after surgery. Most dogs will continue to cough after the surgery and for the rest of their lives, though the cough is usually milder than before surgery. Some dogs will continue to have clinical signs if collapse of the airway progresses above and below the rings and into the smaller airways (bronchial collapse). At this time bronchial collapse cannot be surgically treated in little dogs.
Stents placed inside of the trachea can also cause irritation and coughing. If enough inflammation occurs, the dogs can develop thick tissue in front of or behind the stent that blocks part of the airway (Figure 9). The tissue may shrink with steroid treatment. Stents that are placed in the neck or at the level of the thoracic inlet, where the trachea bends into the chest, are likely to break because of all the motion (Figure 8), so they are usually placed only within the lower part of the trachea. Even there, the stent can break in dogs that cough continuously. Stents that are too small can also shift forwards or backwards and therefore no longer support the narrowed area.
Figure 9. This dog developed "granulation tissue"- thickening from inflammation around the ends of the stent- which shrank after the dog was treated with steroids.
Figure 10. The stent in this dog (Figure 10a) was placed at the level of the thoracic inlet (arrows), where it was stressed by normal neck movement. The stent subsequently broke (Figure 10b) and narrowed (arrows), causing the dog's clinical signs to return.
Figure 10b
Aftercare
Medical management is continued after the surgery, and most dogs are placed on a course of steroids to reduce swelling and irritation from the ring or stent placement. Owners must continue to keep their dogs thin and avoid exposing them to smoke or other airway pollutants. Also, they should use a harness that is specially made to fit low on the chest so that no pressure is put on the neck area when the dog is being walked. In winter months, a humidifier may help relieve irritation from dry, heated air.
Prevention and prognosis
At this time there is no known prevention for tracheal collapse, although reducing weight or exposure to airway irritants such as smoke may help. About 70% of dogs that are treated with medical management alone will show some improvement. About 20% of dogs that undergo tracheal ring placement will require a tracheostomy- a temporary or permanent breathing hole in the neck. About 75% of dogs improve after surgical placement of rings. Dogs that are older than 6 years of age or that have laryngeal or bronchial disease have more complications and a poorer long-term outcome. Of dogs that receive stents, 95% are immediately improved and 90% are markedly improved at the time of recheck. Control of coughing is important for a good outcome, and dogs with bronchial collapse (and therefore continued coughing) are much more likely to have problems after stent or ring placement.
—DJ Krahwinkel, DVM
Diplomate ACVS
—Karen Tobias, DVM, MS
Diplomate ACVS
Posted 8/23/2006
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