What does “brachycephalic” mean?
Brachy means shortened and cephalic means head. Dogs that are described as brachycephalic have skull bones that are shortened in length. This gives the face and nose a flattened, “pushed-in” appearance. Due to the shorter bones of the face and nose, the anatomy and relationship with the other soft tissue structures are altered. The throat and breathing passages of these dogs are frequently undersized or flattened, restricting the dogs’ ability to breathe efficiently.
What is brachycephalic airway syndrome?
Not all brachycephalic dogs suffer from compromised breathing, but many do. Brachycephalic airway obstructive syndrome (BAOS) is a condition affecting short-nosed dogs that can lead to severe respiratory distress. There are several different anatomical abnormalities that contribute to this syndrome, all of which occur more commonly in brachycephalic breeds.
Stenotic nares are abnormally small or narrowed nostrils. The narrowing restricts the amount of air that can flow into the nostrils. The malformed nostrils may also collapse inward as the dog inhales, making it difficult for the dog to breathe through its nose.
Elongated soft palate is a condition where the soft palate (the soft part of the roof of the mouth behind the hard palate) is too long so that the tip of it protrudes into the airway and blocks the entrance to the trachea (windpipe). This obstruction interferes with the movement of air into the lungs.
Laryngeal saccules are small sacs or pouches that are located just inside the larynx (throat box) in front of the vocal cords. In the condition known as everted laryngeal saccules, these saccules evert, or turn outward, and are sucked into the airway by the pressure created with the increased respiratory effort from the stenotic nares or elongated soft palate. Everted laryngeal saccules will further obstruct airway flow.
Nasopharyngeal turbinates are ridges of bone covered by tissue that help humidify and warm the air that is inhaled. Extended nasopharyngeal turbinates extend past the nose and into the pharynx, which is the area behind the nose and mouth, and cause obstruction of the airflow.
Laryngeal (voice box) collapse is caused by the chronic stress placed on the cartilage of the larynx by other conditions of BAOS. Eventually the larynx is not able to open as wide as normal, which causes further restriction in airflow. Over time, the laryngeal cartilages may become paralyzed. This condition does not allow for adequate air intake and may result in sudden death by asphyxiation.
Because all these components make it more difficult to breathe in situations of exercise, stress or heat, dogs with these abnormalities may be unable to take deep enough breaths or breathe fast enough to blow off carbon dioxide or cool themselves. This leads to respiratory distress and further increases the heart and breathing rates, creating a vicious cycle that can quickly become fatal.
Dogs experiencing a crisis due to BAOS benefit from oxygen therapy, cool temperatures, sedatives and, in some cases, more intense medical intervention including intubation. I have found these dogs respond well to being placed in front of a fan.
What are the signs of BAOS?
All the airway abnormalities that make up BAOS cause breathing problems. Most dogs with this syndrome breathe more easily through their mouths than their noses. The more BAOS components present, the more severe the signs.
Mildly affected dogs have noisy breathing, especially with exercise, and most will snort when excited and snore when relaxed or asleep. Severely affected dogs have louder airway noise, tire easily, and may collapse or faint after exercise. Signs tend to be worse in hot and humid weather. Affected dogs are prone to overheating, since they are unable to cool themselves effectively.
BAOS dogs may sleep with a toy between their teeth to keep the mouth open to compensate for the nasal obstruction. Many dogs with elongated soft palates prefer to sleep on their backs. This is probably because this position allows the soft palate tissue to fall away from the larynx, opening the airway.
There may be bluish-purple discoloration of the tongue and gums. This is called cyanosis and is the result of poor blood oxygenation in the lungs.
Symptoms tend to progress with age and typically become severe by 12 months of age. Many owners of brachycephalic dogs become used to the snoring and wheezing signs of airway compromise and perceive them as normal until a particularly severe attack occurs.
While waking from anesthesia, most dogs that are intubated will try to spit out their endotracheal tube. Brachycephalic dogs, however, are often content to leave the tube in place as it provides an open airway and makes breathing easier.
How is BAOS diagnosed?
This syndrome is diagnosed on the basis of the dog’s appearance, clinical signs and the results of a physical examination by a veterinarian. Stenotic nares can be diagnosed on visual inspection. Diagnosis of an elongated soft palate, everted laryngeal saccules or other anatomical changes in the mouth and throat will require heavy sedation or full general anesthesia.
Generally, brachycephalic breeds have a thick tongue, which makes visualization of the larynx in an awake dog very difficult. Attempts to restrain the dog and pull the tongue out enough to look down the throat are usually unsuccessful. Your veterinarian may also recommend chest X-rays to evaluate your dog’s heart and lungs.
Is there treatment for BAOS?
Since obesity worsens the signs of BAOS, weight loss is an important part of treatment if your dog is overweight. For dogs with only mild or moderate signs, the condition may be managed conservatively by controlling exercise and avoiding overheating and stress.
Corticosteroids, non-steroidal anti-inflammatories (NSAIDs) and oxygen therapy may all be useful for short-term relief of airway inflammation or respiratory distress. However, medical management of this condition does not correct the underlying anatomical abnormalities.
Surgery is the treatment of choice and consists of procedures to widen the nostrils, remove the excess tissue of an elongated soft palate, and remove everted laryngeal saccules. Early treatment prevents secondary complications from developing. These complications include bleeding, pain, and swelling during and after the surgery. When these procedures are performed with surgical lasers, the risk of complication is greatly reduced.
Occasionally, a temporary tracheostomy must be performed. An incision is made the neck through the trachea (windpipe), and a tube is sutured in place to allow the dog to breathe until the swelling in the nose and throat subsides enough that the dog can breathe normally on its own.
In chronic cases in which the laryngeal cartilages have become rigid and inflexible, removal of the elongated soft palate and laryngeal saccules may not provide enough relief. The creation of a permanent tracheostomy, which is a new permanent opening into the trachea, may be the only solution, although there are complications associated with this procedure as well.
What is the prognosis for dogs with BAOS?
The overall prognosis for dogs with BAOS depends on how many anatomic abnormalities are present and how old the dog is at the time of treatment. The prognosis is good for young dogs following corrective surgery. They breathe much easier and have significantly reduced respiratory distress. These dogs are able to lead more active lives.
Older dogs have a more guarded prognosis, especially if the process of laryngeal collapse has already started. If the laryngeal collapse is advanced, the prognosis is poor. Appropriate management can significantly improve the quality of life for these dogs.