One of the most common causes of chronic coughing in toy and small breed dogs is collapsing trachea. The Meowing Vet discusses the typical clinical signs and treatments of this airway disorder and warns pet owners of its potential complications.
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What is a collapsing trachea? What causes it?
Collapsing trachea, also called tracheal collapse or tracheobronchomalacia, is caused by narrowing of the diameter of the lumen of the trachea. This means that the hollow portion inside your dog’s trachea (or windpipe) becomes narrowed, reducing the normal flow of air through the windpipe. This results in coughing and can lead to a respiratory crisis (dyspnea) in some cases during which your dog may have difficulty breathing. This can be fatal. Turbulent airflow through this narrowed trachea, which can cause inflammation and swelling (edema) of the tissues in the respiratory tract, can increase the likelihood of developing secondary respiratory infections and pneumonia and can also be an additional complicating cause of respiratory distress.
Now that we have collapsing trachea defined, let’s discuss what causes it. Normally, the tissue of the windpipe is held open like a garden hose by the rigid cartilage rings that partially surround the outer circumference of the trachea down its entire length. Gently feel along either side of your own windpipe at your neck, and you may be able to feel your own tracheal cartilage rings. These cartilage rings are C-shaped, being incomplete at the dorsal (or top) aspect of the trachea. With collapsing trachea, the composition of these cartilage structures may start to degrade, becoming weaker and weaker until a portion of the trachea is no longer held rigidly open and may start to sag inward, disrupting airflow. The trachea becomes wider and flatter. The degenerative change of the structure of the tracheal cartilage is not fully understood but is thought to have a hereditary component. This process will progress over time, and additional cartilaginous rings may also start to degrade.
Some dogs may also have a redundant tracheal membrane, excessive tissue at the dorsal aspect (or top) of the trachea that may sag downwards into the tracheal lumen, thus disrupting the normal flow of air. Some veterinarians consider a redundant tracheal membrane to complicate or be a component of collapsing trachea in some canines.
Any portion of the trachea may be affected, including the cervical or extra-thoracic portion (the length of trachea in the neck region) and intra-thoracic portion (the length of the trachea located within the chest cavity). Sometimes cartilaginous degeneration of the entire length of the trachea may occur. Moreover, the mainstem bronchi (singular: bronchus) may also be affected; the intra-thoracic trachea eventually splits into a left bronchus and right bronchus, which carry air to the left and right lung, respectively. Bronchial involvement can be more difficult to treat in some cases.
The severity of tracheal collapse varies among individual dogs. Grade I indicates a 25% decrease in the diameter of the tracheal lumen caused by sagging of the dorsal (top) portion of the windpipe. Grade II represents a 50% decrease due to degeneration in the stability of the cartilaginous rings. Grade III means a 75% decrease with flattening of the cartilage rings, while grade IV means flattening with 100% collapse — a true emergency in which air is not able to pass through this cave-in to make its way to the lungs, and the dog will enter respiratory distress and die without proper veterinary aid.
Which dogs are most at risk?
Toy breeds and small breed dogs that are middle-aged to geriatric are most likely to develop collapsing trachea. As mentioned, a genetic predisposition is suspected. The average age of onset ranges from 4 – 14 years. The most common breeds affected include, but are not limited to:
- Miniature poodles
- Yorkshire terriers
- Chihuhuahs
- Pomeranians
Occasionally, younger large-breed dogs may also be affected. Cats rarely develop collapsing trachea.
Clinical Signs of Collapsing Trachea
- Coughing
- A gradually developing, chronic cough is the most common sign of a collapsing trachea.
- Dry cough
Non-productive cough (i.e. typically no foam or phlegm coughed up unless concurrent secondary respiratory infections or pneumonia)- Coughing may be triggered by or worsen with excitement or exercise activity as well as hot and humid weather.
- May increase in frequency and severity over time
- Gagging or retching after coughing or after eating or drinking
- Increased effort when breathing
- Greater effort when inhaling points to extra-thoracic or cervical involvement (meaning that the portion of the trachea is affected in the neck region before it extends down into the chest cavity)
- Greater effort when exhaling occurs with intra-thoracic involvement (i.e. the portion of the trachea inside the rib cage is affected)
- Sometimes a high-pitched, goose honking sound when breathing in (i.e. inspiratory stridor): This is a sign of laryngeal paralysis, dysfunction of the nerves that open the larynx (the opening to the trachea) during breathing and close the larynx upon swallowing to prevent aspiration into the respiratory tract. Roughly 30% of dogs with tracheal collapse may also have concurrent laryngeal paralysis (“lar par”).
- Can cause respiratory distress (dyspnea) in some instances, an EMERGENCY requiring prompt veterinary attention! If you notice that your dog is gasping for air, panting excessively, or has blue gums or skin (cyanosis), take your pup to the nearest veterinary center ASAP! Unfortunately, sudden death can sometimes occur in cases of full tracheal collapse.
Diagnosis
- Physical examination: Tracheal sensitivity that results in coughing upon palpation (or gentle compression) of the cervical trachea by your veterinarian is a common feature of collapsing trachea. A veterinary physical exam will also allow your vet to discover other causes of tracheal impairment unrelated to collapsing trachea, including enlarged lymph nodes in the neck region as well as other masses that may be compressing the windpipe.
- Radiographs of the neck and chest (i.e. cervical and thoracic X-rays): Because tracheal collapse is a dynamic process (meaning the luminal diameter of the windpipe may become transiently narrowed in diameter only during certain phases of respiration), static radiographic images may not always be able to capture a picture of the trachea at the time that it is most narrowed. However, radiographs still yield much diagnostic information. X-rays can reveal a redundant tracheal membrane and are also still useful in ruling out other causes of coughing in dogs, including congestive heart failure (CHF), bronchitis, and pneumonia.
Fluoroscopy: Since the diameter of the tracheal lumen may become more or less narrowed at different times as your dog takes a breath, wouldn’t it be nice if we could uninterruptedly watch the trachea move instead of taking random snapshots via X-ray images? Luckily, some veterinary centers have the tool of fluoroscopy, which is like a real-time movie version of a still X-ray image. Fluoroscopy is a non-invasive means of observing the dynamic movement of the trachea during inhalation and exhalation.- Ultrasound: Some veterinarians may also be able to visualize sagging of the dorsal (top) portion of the trachea via ultrasound of the neck.
- Tracheoscopy: Passing a scope with a camera on the end down the trachea is also an excellent visualization tool. Tracheoscopy must be performed under general anesthesia. It is considered an ideal gold standard for proper diagnosis of tracheal collapse. Scoping of the lower airways is termed bronchoscopy.
- Tracheal wash: In order to rule out other inflammatory and infectious causes of cough that can mimic, complicate, or themselves be secondary complications of collapsing trachea, your vet may wish to perform a tracheal wash in which a small amount of sterile fluid is instilled in the windpipe and then drawn up to collect a sample of fluids and cells in the upper respiratory system. Certain cancerous cells and infectious agents, such as kennel cough, parasites of the respiratory tract, as well as bacterial and fungal causes of pneumonia can be detected via this manner. Sampling from the lower airways is termed bronchoalveolar lavage (BAL).
Treatment
Unfortunately, collapsing trachea is not curative, and the condition is likely to progress despite the therapies discussed below. These treatments, however, are intended to improve the quality of life of dogs affected with tracheal collapse and to help reduce the critical risk of respiratory distress. Implementing proper lifestyle changes and a tailored medical therapy plan are the most important components of managing tracheal collapse. Surgical intervention has its place in some cases, but due to its potentially very risky side effects and non-curative nature, it is a last-ditch salvage procedure used as a final resort in cases retractable to medical therapy.
Lifestyle changes
Weight management is so, so important for improving the overall quality of life of all pets, including dogs with collapsing trachea. Obesity causes your pet to make more of an effort when breathing, so maintaining a healthy weight will greatly improve your pet’s respiratory tract and will help in cough reduction. Talk to your personal vet about safe weight loss tips if your dog is on the heavier side.- Try to keep your dog calm to reduce over-excitement and prevent heavy exercise, which can trigger coughing. Light exercise is good for your pet if he or she can tolerate it without coughing fits or respiratory distress. Overly anxious dogs who become excited so easily that they begin coughing severely may require behavior modification or anti-anxiety medications if indicated by your vet.
- Keep your dog cool during hot and humid weather.
- Keeping up-to-date on your dog’s vaccines, including kennel cough (canine infectious tracheobronchitis) and canine influenza if you live in an endemic area. Respiratory infections can exacerbate the clinical signs of collapsing trachea, so preventing as many as we can from occurring is important.
Medical Therapies
These medications are the therapeutic mainstays of managing most cases of tracheal collapse. Your veterinarian will prescribe a tailored plan for your individual pet based on his or her needs. The plan may become altered over time depending on your dog’s response or the progression of collapsing trachea. Many dogs require daily, lifelong medical therapy.
Antitussives (i.e. cough suppressants)
- Examples: hydrocodone (syrup or tablet form)
- Antiinflammatory doses of corticosteroids to reduce swelling of the tissues of the trachea, which can occur due to turbulent airflow through a narrowed trachea hitting up against them
- Examples: prednisone, prednisolone
- Bronchodilators to open up the lower airways
- Examples: theophylline, terbutaline
- Antibiotics or antifungal drugs if there is a concurrent respiratory tract infection
Surgery
As previous mentioned, surgical intervention for cases of collapsing trachea is to be performed only as a last resort. It is non-curative and is merely a salvage procedure that may buy your pet a bit more time. It is typically performed by veterinary surgeons with specialized training, and many surgeons are hesitant to perform such a surgery due to the high likelihood of intraoperative and post-op complications.
Such surgery involves either placing a rigid stent inside the tracheal lumen to hold it open (an endoluminal stent, a.k.a. intraluminal stent) or else around the outside of the trachea 
like a collar to pull the trachea open (an extraluminal stent, more technically categorized as either prosthetic tracheal rings or a spiral prosthesis). Endoluminal stents are preferred by most surgeons. Cases of cervical (or extra-thoracic) tracheal collapse are easier surgical procedures in comparison to intra-thoracic collapses in which the chest cavity must be entered.
Complications of extraluminal procedures include laryngeal paralysis, tracheal necrosis (a potentially fatal death of the tracheal tissue around the surgical device), and pneumothorax (i.e. free air outside the lungs in the chest cavity that can interfere with breathing). Complications of endoluminal stents include an overwhelming inflammatory response to the device that causes granulation tissue to form around it as well as stent migration in which the stent can dislodge and cause fatal respiratory crisis if pieces migrate down the airway. Other complications that can occur with both procedures include laryngeal spasm (which can be deadly), tracheal tear, infection, and hemorrhage. That being said, many veterinarians do not advise for such surgeries and may discuss peaceful euthanasia as a kinder yet admittedly very difficult alternative. However, even with successful surgeries, daily medication is still required, respiratory infections can complicate matters, and progression of the airway disease will likely still occur.
Emergency Treatments
In the case of a respiratory emergency in which your dog is having difficulty breathing, your vet will provide oxygen supplementation, may use a nebulizer to deliver inhaled drugs to open up the airways, and shall administer corticosteroids to reduce swelling as well as anti-anxiety medications (anxiolytics) to calm your dog and help reduce panting to ease the flow of air through otherwise swollen airways. In severe cases of cervical tracheal collapse, your vet may place your pet under general anesthesia in order to place a endotracheal tube down your dog’s trachea to provide a patent airway. In the case of a grade IV/100% tracheal collapse, your vet will discuss the possibility of surgery or euthanasia due to the severity of disease and non-response to medical therapies.
Prognosis
The severity and overall long-term prognosis of tracheal collapse truly varies from dog to dog. The extent of tracheal and possibly bronchial involvement may also differ, with some dogs having only a small portion of their airway affected while others may suffer degeneration along the entire length of their trachea to various degrees of severity. Although this airway disorder is incurable and will progress over time (even with surgical stenting), the rate of progression differs among individuals. Some dogs will fortunately remain pretty stable throughout their lifetimes, and their coughing and other clinical signs will be well-managed with medical therapy and proper lifestyle changes. Other dogs, however, may worsen over time and develop complications from pneumonia or a dyspneic crisis that may require peaceful euthanasia due to lack of response to medical and surgical intervention and overall poor quality of life.
– Maranda Elswick, DVM
The Meowing Vet recommends that you follow up with your personal veterinarian if you suspect collapsing trachea in your dog based on the clinical signs discussed in our article.
