Brachycephalic Obstructive Airway Syndrome = Short and Flat-Faced Dogs
Most lay people are not familiar with the term brachycephalic, but if you own a Persian cat, Pug dog, Boston Terrier, Pekingese, Boxer, Bulldog, Shih Tzu, French or English Bulldog, any one of the other myriad breeds with smooshed or short faces OR a mixed breed animal with any of these and short nose, you should become familiar with this word and all the baggage it carries. The word comes from the Greek roots brachy, meaning short and cephalic, meaning head.
Brachycephalic dogs have been overbred to possess a relatively normal lower jaw in proportion to their body size and a compressed nasal bone/upper jaw. This occurs because when the puppy is growing, there is a genetic defect resulting in early growth plate closure. The early cessation of nasal bone growth results in the rest of the structures inside the nasal cavity continuing to grow (ie: redundant nasal turbinate bones) plus narrow to pinched off nostrils (the ultimate cause of elongated soft palate and everted laryngeal saccules). English Bulldogs also have a hypoplastic (very small) trachea. In promoting this cosmetic appearance, breeders and, out of ignorance vs actual nefarious drive, people purchasing these dogs/cats, have severely compromised the welfare, health, quality of life and life span in these breeds. If you own a brachycephalic breed, dog or cat, you are obligated to educate yourself and become familiar with the additional surgical, medical and husbandry needs of your pet.
The Respiratory System & Brachycephalic Obstructive Airway Syndrome (BOAS)
Brachycephalic breeds make a lot of snorting respiratory sounds secondary to obstructed airflow because of the way their nostrils, nasal passages and the back of their mouths are shaped. These sounds are generated from the combination of anatomic deformities described below. These deformities occur in every brachycephalic breed and other breeds mixed with brachycephalic breeds to varying degrees of severity. Brachycephalic dogs have limitations that must be recognized – they do not tolerate high temperatures or moderately high/high humidity because their ability to regulate their body temp by panting is significantly reduced. They also can develop a sequalae of difficulty breathing called laryngeal collapse – this is one of several possible breed-related respiratory emergencies and requires a hole in the trachea because the upper airway is obstructed, often permanently.
Stenotic Nares
This is the medical terminology for narrowed nostrils. The brachycephalic animal’s respiratory passages begin with very small, often slit-like, nasal openings for air to enter the nasal cavity. This causes excessive open-mouth breathing and panting as the small openings result in much more resistance to moving air into the nasal cavity, across the tortuous turbinate bones inside the nasal cavity, past the often-swollen palate and larynx, down a too-small trachea and into the lungs. Think of how difficult it is to fill your lungs if you hold your nose and try to inhale through a straw – that is how these animals feel with every breath they take. Stenotic nares can be surgically widened which can drastically help many animals.
Elongated Soft Palate
It is difficult to fit the soft tissues of the canine and feline, to some degree, mouth and throat into the brachycephalic animal’s short face. As a result, the soft palate, which separates the nasal passages from the oral cavity, flaps loosely down into the throat, obstructing the laryngeal opening and causing strangling/stridorous sounds. Virtually all brachycephalic dogs suffer from this to some degree. The English and French Bulldogs, typically the most severely deformed of the brachycephalic breeds, can often have more severe clinical signs of BOAS. Excess barking and panting leads to swelling in the throat that can lead to respiratory collapse. The palate can be surgically shortened and some animals may need to have this procedure performed several times in their lifetime.
Tracheal Stenosis/Hypoplastic Trachea
The trachea is also known as the windpipe. The brachycephalic animal may have an abnormally narrow windpipe. If the trachea is unexpectedly small, intubation may be delayed or not be possible and it is important to know this in advance of any planned surgical procedure. The English bulldog is particularly predisposed to this anatomical defect. There is no treatment for this abnormality.
Everted Laryngeal Saccules
The normal larynx has two small pockets called ventricles or saccules. When a dog has increased effort to breathe, over time these little pockets can turn inside out and obstruct the throat. This condition can be corrected surgically; however, it can resolve on its own after the stenotic nares are corrected. The Pug seems to be especially predisposed to this situation.
Enlarged Tongue (macroglossia)
The brachycephalic dog’s tongue can be particularly thick and wide, contributing to overall airway obstruction. The French and English bulldogs seem particularly predisposed to this issue.
Heat Stress, Excitement, and Exercise
Because of these upper respiratory obstructions, the brachycephalic dog’s panting is inefficient. A dog with a more conventional face and throat moves air quickly over the tongue while panting. Saliva evaporates from the tongue as air passes across the moist surface and the blood circulating through the vessels near the surface of the tongue is also cooled and circulated back to the rest of the body, helping to lose heat and reduce the internal body temperature. In brachycephalic dogs, so much extra work is required to move the same amount of air due to airway resistance and obstructions in the airway, that the tissues lining the airway become swollen and thick. This inflammation leads to more severe obstruction, distress and often heat injury or heat stroke, which is a life-threatening emergency. These details should always be considered during stressful situations, especially air travel. The American Veterinary Medical Association publishes travel guidelines for brachycephalic pets.
The American College of Veterinary Surgeons has further information on brachycephalic obstructive airway syndrome (BOAS).
Brachycephalic dogs are the most likely to develop heat stroke.
Altogether, the upper airways of the brachycephalic dog compromise the ability to effectively and efficiently move air into and out of the lungs. Under normal conditions the compromise does not cause significant problems; however, owners should take care not to let the dog become overweight or get hot in the summer. These animals should not be exercised when it is more than 80F outside or if the humidity is greater than 40-50%. Should your dog require general anesthesia or sedation – anesthetic risk is inherently higher than in a nonbrachycephalic breed. Generally, most animal hospitals are equipped and experienced in managing the special needs of BOAS animals.
BOAS is typically progressive over the life of the animal. Even if surgical intervention is elected at a young age, some more severely affected dogs require additional surgery or go on to develop laryngeal collapse and require a permanent tracheostomy (a hole in the throat for breathing).
Gastrointestinal Tract
There are stomach and swallowing issues that correlate to the increased abdominal and intrathoracic pressures caused by the components of BOAS. In brachycephalic breeds, the esophagus (the tube that conducts swallowed food from the throat to the stomach) experiences reflux of stomach contents – like reflux or heartburn in humans. This reflux generates pain and inflammation. Compounding this problem is the retention of food in the stomach for prolonged periods. Pooling of food in the stomach creates a sensation of nausea and increases the potential for vomiting and/or stomach acid reflux. The English and French bulldogs seem particularly predisposed to these GI issues. This may seem like a separate issue from BOAS, but in fact, the reflux, regurgitation and even herniation of part of the stomach into the chest cavity stems from the extreme inhalation efforts made against the upper airway obstruction that results from the shape of the brachycephalic animal’s nose/back of the throat. Medications are helpful for intestinal issues as is weight control, but often correcting the upper airway obstruction significantly improves gastrointestinal problems as well.
Chronic corneal exposure and irritation/trauma
With most of the nasal bones compacted, brachycephalic dogs tend to have trouble with the way their eyes sit in their heads. The eye sockets are shallow making the eyes especially prominent and vulnerable. Often a fold of nasal skin will rub on the eyeball or there can be eyelashes rubbing on the eyes. This constant irritation and trauma to the cornea can result in ulcers, and pigmentation that obscures vision and pain.
Lagophthalmos
Sometimes, the eyes are so prominent that the lids cannot close all the way over them. This leads to irritation and drying of the center of the eye and sometimes repeated ulceration, pain and possible blindness unless surgical correction is performed. If you cannot tell by watching your pet blink, watch as your pet sleeps to be sure the eyelids close all the way. If the eyelids cannot protect the eyes, pigmentary changes will form where the eyes are chronically irritated and can ultimately cause blindness.
Modified from Brachycephalic Airway Obstruction Syndrome in Flat-Faced Dogs-Veterinary Partner – VIN, accessed 12/21/22, 4:25 PM
Nasal Fold Irritation
Many brachycephalic dogs have a fold of skin between the nose and eyes. This skin fold may need regular cleaning as it tends to collect skin oil and moisture but it can also be prominent enough to rub on the actual eyeball. Chronic irritation will show as a pigmented area on the eye surface, especially on the side nearest the nose. This is hard to see without a bright light if it is noted, a search for the cause is warranted. Depending on the location of the pigmentation, surgery may be recommended.
Entropion (Turned-In Eyelids)
The shortened face leads to rolling of the eyelids in such a way that the eyelashes or even haired skin can rub the eye. This is not only uncomfortable but will damage the eye. Some dogs have eyelids that droop or turn out in one area but turn inward in another area (usually the corner of the eye). Surgical correction may be needed to protect the eye and restore comfort.
Dry Eye (Keratoconjunctivitis Sicca)
Brachycephalic breeds tend to get more than their share of tear production problems. In this situation, inadequate tears are produced so a thick, goopy, yellow eye discharge results. In response to the irritation, the eye becomes pigmented and can become blind if treatment is not instituted. This condition is treatable with medication so it is important to recognize it before it progresses to a point where vision is lost and the goal is simply restoring comfort.
Risk of Proptosis
Recognize the prominence of the eyes on brachycephalic. The bony eye sockets are very shallow. This means that any blow to the back of the head, even a fairly minor one, can cause an eye to pop from its socket (proptosis) and require surgical replacement even removing the eye. This can happen also with too much pulling against the leash if the pet is wearing a collar. You may wish to consider a harness for your pet. Traumatic proptosis frequently blinds the eye that was popped out.
Other Concerns
The normal dog has 42 teeth in the mouth. The brachycephalic dog also has 42 teeth but a lot less space to fit them in. This means that the teeth will be crowded and growing in at oddangles which, in turn, traps food debris and leads to periodontal disease at a far younger age than in non-brachycephalics. The earlier you begin using home care dental products, the longer you will be able to postpone full dentistry under general anesthesia.
As mentioned, skin fold infections are common amid the facial folds of the brachycephalic breeds. Be sure to examine these areas periodically for redness. Even if the fold does not rub on the eyeball, it will likely need regular cleaning and topical disinfection.
The broad-headed nature of these breeds makes reproduction a tricky matter as a Cesarean section is frequently needed. Difficult labor is common and, as surgical assistance is often necessary, it is important not to breed females with tracheal stenosis (see above). Brachycephalic breeding is not for the inexperienced.
Altogether, the brachycephalic breeds show plenty of personality and intelligence, just as all dogs do, but because of their specific needs, their owners need extra knowledge. If you have any questions about your brachycephalic dog, don’t hesitate to call your veterinarian.
URL: https://veterinarypartner.vin.com/doc/?id=4951534&pid=19239f9cf1801-4bd2-4642-97e6-84efa68683eb.1671668713 accessed 8 AUG 24
Modified from Wendy Brooks, DVM, DABVP
Reviewed/Revised: 05/05/2021
Brachycephalic Obstructive Airway Syndrome (BOAS) = flat-faced animals
This condition is also known by other names including brachycephalic syndrome, brachycephalic airway syndrome, brachycephalic respiratory syndrome, or congenital obstructive upper airway disease.
What constitutes a brachycephalic dog or cat?
This is a scientific term describing a dog that has a shortened muzzle (or nose) due to its genetics (breed). The skull bones of these dogs are compressed such that the dog has a more flattened or “pushed-in” facial conformation compared to other dogs.
What breeds of dogs are considered brachycephalic?
This condition is seen most frequently in the English bulldog, Pug, French bulldog and Boston terrier. Other affected breeds include the boxer, Pekingese, Shih-Tzu, Chinese sharpei, Lhasa apso, and bull mastiff.
What problems are associated with this condition?
The anatomical variations of the skull bones result in abnormalities of the upper respiratory system. Overall, there can be varying degrees of breathing difficulty depending on the extent of the abnormalities. The severity of symptoms may increase as the dog ages.
• Noisy breathing (e.g. snoring, wheezing, snorting)
• Reduced inability to exercise
• Gagging when swallowing food or water
• Labored breathing/heavy panting
• Open mouth breathing
• Bluish coloration (instead of pink) of the gums
• Collapse
• Heat Intolerance
What causes BOAS?
There are several respiratory tract variations and some or all of them can be found in an individual dog. All of them contribute to the obstruction of airflow from the nose to the lungs and significantly increase resistance to airflow into the lungs, making it incredibly difficult for these animals to move air from the outside into their lungs.
The major findings include:
• Stenotic nares are congenitally small nostrils that may also collapse as the dog inhales
• An elongated soft palate can cause obstruction of airflow into the larynx
• Everted laryngeal saccules refer to tissue near the vocal cords that are pulled inward during inhalation in these animals and can block airflow
• Some dogs may have a windpipe that is proportionally too narrow, the most common in English Bulldogs, and is referred to as a hypoplastic trachea
• Redundant nasopharyngeal turbinate bones that are crowded and tortuous inside the nasal passages, further reducing airflow and increasing resistance.
Other possible findings that can contribute to airflow obstruction include:
• Laryngeal collapse
• Large tongue
• Enlarged or everted tonsils
Over time the condition worsens because of the dog working harder to breathe. Tissues in the throat can become swollen or inflamed, further obstructing the flow of air.
How is BOAS diagnosed?
Most dogs are diagnosed between one and four years of age. Males and females are affected equally.
The diagnosis is made based on a combination of factors including the breed of dog, symptoms and physical examination findings. Stenotic nares are observed during routine exams. Further evaluation requires your dog to be lightly anesthetized to assess the soft palate, larynx and laryngeal saccules. The diameter of the trachea can be assessed by taking X-rays of the neck and chest. Advanced testing can include an endoscopy or a CT scan of the upper airway.
How is BOAS treated?
Mild cases can be treated conservatively.
- Maintenance of a healthy weight/weight loss
- Minimize panting
- Avoid of excessive heat and humidity
- Controlled physical activity and eliminating outdoor physical activity when the temperature is over 80F or humidity is greater than 50%.
- Minimize stress
- Use a harness instead of a neck collar
More severe cases require surgical correction. The earlier intervention leads to better outcomes but many dogs will require additional surgery later in life because the redundant/tortuous turbinate boned cannot be remedied and will continue to cause difficulty moving air into the lung through the nasal passages.
- A consultation with a veterinary surgeon experienced in the component of BOAS surgery is recommended for ALL flat-nosed dogs and cats.
- Stenotic nares can be treated by removing a small wedge of tissue to make the openings larger.
- Everted saccules can be excised.
- If the soft palate is elongated and edematous, contributing respiratory problems, it can be shortened surgically.
- There is no surgical procedure to correct a hypoplastic trachea.
- There are anesthetic risks associated with these patients.
- Surgical risks include bleeding and swelling
- A temporary tracheostomy may be necessary in some cases
BOAS can become an emergency situation. If your dog is experiencing a respiratory crisis, immediately providing a cooler environment and transport to your veterinarian or nearest emergency hospital is essential.
Treatment may include:
• Sedation
• Oxygen therapy
• Medications to reduce inflammation
• Tracheostomy (either temporary or permanent) to bypass the upper airway obstruction
Other conditions associated with BOAS
• Laryngeal collapse can occur as a result of chronic upper airway obstruction
• Bronchial collapse is often associated with laryngeal collapse
• Gastrointestinal disorders such as hiatal hernia and gastroesophageal reflux can improve following treatment for BOAS
• Aspiration pneumonia
What are the possible outcomes?
• Dogs with milder cases of BOAS can have normal life expectancies.
• Early surgical intervention (dogs under 2 years of age) leads to better outcomes.
• Dogs with laryngeal collapse have less favorable outcomes, with or without surgery.
• Dogs with milder or fewer defects have a better prognosis.
• There are risks of complications including mortality associated with surgery.
Prevention
Because this is a genetic condition, dogs that have difficulty breathing, require surgical therapy, or that have a hypoplastic trachea should not be considered for breeding.