Brachycephalic airway obstructive syndrome
Brachycephalic syndrome is a pathological condition affecting short nosed dogs and cats which can lead to severe respiratory distress. There are four different anatomical abnormalities that contribute to the disease, all of which occur more commonly in brachycephalic breeds: an elongated soft palate, stenotic nares, a hypoplastic trachea, and everted laryngeal saccules (a condition which occurs secondary to the other abnormalities). Because all of these components make it more difficult to breathe, in situations of exercise, stress, or heat, an animal with these abnormalities may be unable to take deep or fast enough breaths to blow off carbon dioxide. This leads to distress and further increases respiratory rate and heart rate, creating a vicious cycle that can quickly lead to a life-threatening situation.
Dogs experiencing a crisis situation due to brachycephalic syndrome typically benefit from oxygen, cool temperatures, sedatives, and in some cases more advanced medical intervention, including intubation.
Causes and risk factors
- Stenotic nares (narrowed nostril)
- Elongated soft palate
- Hypoplastic trachea (reduced trachea size)
- Short/irregular nasal turbinate
Muzzle length scales with the risks of brachycephalic syndrome. Other risk factors identified include neck girth and body condition score.
Signs and symptoms
- Dyspnea (breathing difficulty)
- Noisy/labored breathing
- Stridor (high pitched wheezing)
- Continued open-mouth breathing
- Extending of head and neck to keep airway open
- Sitting up or keeping chin in an elevated position when sleeping
- Sleeping with toy between teeth to keep mouth open to compensate for nasal obstruction
- Cyanosis (blue/purple discoloration of the skin, due to poor blood oxygenation in the lungs )
- Sleep apnea
- Stress and heat intolerance during exercise.
Symptoms progress with age and typically become severe by 12 months.
Despite observing clinical signs of airway obstructions, some owners of brachycephalic breeds may perceive them as normal for the breed, and may not seek veterinary intervention until a particularly severe attack happens.
After awaking from surgery, most dogs that are intubated will try to claw out their tracheal tube. In contrast, brachycephalic dogs often seem quite happy to leave it in place as it opens the airway, making it easier to breathe.
Other conditions may be observed concurrently. These include swollen/everted laryngeal saccules, which further reduce the airway, collapsed larynx, and chronic obstructive pulmonary disease caused by the increased lung workload.
Brachycephalic syndrome has been linked to changes in the lungs, as well as the gastrointestinal tract including bronchial collapse, gastroesophageal reflux, and chronic gastritis.
This syndrome is diagnosed on the basis of the dog's breed, clinical signs, and results of a physical examination by a veterinarian. Stenotic nares can usually be diagnosed on visual inspection. Diagnosis of an elongated soft palate, everted laryngeal saccules, or other associated anatomical changes in the mouth will require heavy sedation or full general anesthesia.
Treatment consists of surgery for widening the nostrils, removing the excess tissue of an elongated soft palate, or removing everted laryngeal saccules. Early treatment prevents secondary conditions from developing.
Potential complications include hemorrhages, pain, and inflammation during and after surgery. Some veterinarians are hesitant to perform soft palate correction surgery. With CO2 surgical lasers, these complications are greatly diminished.
To prevent or limit exacerbation of symptoms, avoid stress and high heated climates. Maintain ideal body weight and avoid overfeeding. Use harnesses instead of collars to avoid pressure on the trachea.
The risk of brachycephalic syndrome increases as the muzzle becomes shorter. To avoid producing affected dogs, breeders may choose to breed for more moderate features rather than for extremely short or flat faces. Dogs with breathing difficulties, or at least those serious enough to require surgery, should not be used for breeding. Removing all affected animals from the breeding pool may cause some breeds to be unsustainable and outcrossing to non-brachycephalic breeds might be necessary.
Other health problems
Non-airway problems associated with brachycephalia may include
- Inflammation in skin folds
- Mating and birthing problems
- Malocclusion - misalignment of the teeth.
- Dental crowding
- Brachycephalic ocular syndrome
- Ectropion/entropion - inward/outward rolling of eyelid
- Macropalpebral fissure
- Lagophthalmia - inability to close eyelids fully
- Exophthalmos/eye proptosis - abnormal protrusion of the eye
- Nasal fold trichiasis - fur around the nose fold rubs against the eye.
- Distichiasis - abnormally placed eyelashes rubs against the eye.
- Poor tear production.
- Gastrointestinal problems
List of brachycephalic dog breeds
- Boston Terrier
- Brussels Griffon
- Cane Corso
- Chihuahua (apple-headed)
- Chow Chow
- Dogue de Bordeaux
- English Mastiff
- French Bulldog
- Griffon Bruxellois
- Japanese Chin
- King Charles Spaniel
- Neapolitan Mastiff
- Shih Tzu
- Valley Bulldog
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