What Is BOAS (Brachycephalic Obstructive Airway Syndrome)?
Wed, April 21, 2021

What Is BOAS (Brachycephalic Obstructive Airway Syndrome)?



Associated with a breed, Brachycephalic Obstructive Airway Syndrome (BOAS) jeopardizes the health of animals who have trouble breathing, explained RSPCA (Royal Society for the Prevention of Cruelty to Animals), the largest animal welfare charity in the UK. Dog breeds such as French Bulldog, Pug, Boston Terrier, and more are likely to be affected by BOAS. Cats such as the Persian and Persian-derived breeds like the exotic shorthair can also have this disorder.

Most brachycephalic animals have BOAS, though not all of them have it. It is a lifelong and progressive disorder, impairing an animal’s ability to exercise, sleep, eat, play, live comfortable lives, and engage in normal behaviors. Extreme brachycephalic dogs live shorter lives than those with less extreme brachycephaly or non-brachycephalic canines.


BOAS In Young, Breeding Age French Bulldogs and Pugs (2019)

M Aromaa, L. Lilja-Maula, and MM Rajamaki of Semantics Scholar, an online research portal, said the brachycephalic population comprised of 44 French bulldogs and 51 Pugs. The authors also had 21 control dog groups representing nine breeds: six Border Terriers, two Cairn Terriers, and seven Miniature Poodles— including one Jack Russel Terrier, West Highland White Terrier, Cavalier King Charles Spaniel, standard Dachshund, Mudi, and Cocker Spaniel.

The authors found that 84% of French bulldogs and 92% of pugs did not have any health complications affecting their daily lives. However, for 36% of French bulldogs and 33% of Pugs, owners said their dogs had exercise intolerance. Two French bulldog and two Pug owners said that respiratory signs limited daily activity.

Gastrointestinal signs, vomiting, or regurgitation were reported to occur every week in 7% of French bulldogs, occasionally in 30% in French Bulldogs, and in 14% of Pugs. Owners also reported a loud upper respiratory noise in 80% of French bulldogs and 82% of Pugs. Owners had noticed that 9% of French bulldogs and 4% of Pugs sometimes slept with their chin elevated, while 5% of French bulldog and 2% of Pug owners noticed that their dog often slept with an item of some sort in their mouth.

According to the owners, 90% of the control dogs did not have any health complications affecting their daily lives, though two dogs had persistent dermatological issues. None of the dogs had exercise intolerance or syncopal episodes. However, vomiting or regurgitation was observed in 38% of control dogs.  

Upper respiratory sounds were assessed at rest during the physical examination. In 55% of French bulldogs and 41% of Pugs, no upper respiratory sounds were observed. In 36% of French bulldogs and 47% Pugs, mild respiratory sounds were recorded, as well as moderate sounds in 7% of French bulldogs and 12% of Pugs. However, severe upper respiratory sounds were observed in one French bulldog, but none in Pugs.

The French bulldogs or Pugs in the study did not have open nostrils. Mild stenosis was observed in 14% of French bulldogs, while 59% and 27% had moderate stenosis and severe stenosis, respectively. Likewise, mild stenosis was observed in 20% of Pugs, while others had moderate (61%) and severe (20%) stenosis. The researchers concluded that exercise tests should be part of the breeding selection assessment for brachycephalic dogs. Future studies should evaluate the long-term impacts of BOAS breeding selection tools like exercise tests on the welfare of offspring. Follow-up studies could be conducted to assess how age impacts the results.   




Symptoms of BOAS

Signs can include increased effort when breathing, noise (snoring sounds) during breathing, exercise intolerance, vomiting and regurgitation, excess salivation, and sudden collapse. Another sign of BOAS is when your dog is more susceptible to heat stroke. If your pet is mildly affected, it will have noisy breathing especially when letting it engage in exercise, stated Krista Williams, BSc, DVM and Cheryl Yuill, DVM, MSc, CVH of VCA, an operator of over 1,000 animal hospitals in the US and Canada.

Severe cases of BOAS have more pronounced airway noise, appear to be exhausted easily with exercise, and may collapse or faint after engaging in physical activity. BOAS has been correlated to changes in the lungs and gastrointestinal tract such as bronchial collapse, gastroesophageal reflux, and chronic gastritis. Since BOAS can affect your dog’s gastrointestinal tract, it can show signs of vomiting, poor appetite, and retching. Dogs with BOAS may develop secondary problems like inflammation of other structures in the airways. In the long run, increased effort in breathing can lead to increased strain on your dog’s heart.


Risk Factors Associated With BOAS

Overweight, elderly, or stressed dogs are more likely to be at risk of BOAS. Animals who are stressed or not used to being in a crate or traveling are more susceptible to this disorder. Traveling by air is not recommended as there have been cases of fatal incidents involving brachycephalic dogs, with many airlines refusing to accept them for air transport because health problems and death may occur.  



Diagnosis of BOAS

Diagnosis will be based on your dog’s breed, signs, and results of its physical examination. Your veterinarian will recommend pre-anesthetic blood work and chest x-rays to assess your pet’s overall health and minimize its risk. This is done because dogs affected by BOAS are likely to have complications linked with general anesthesia.


Treatment of BOAS

Weight loss is a significant part of your dog’s treatment plan as obesity escalates the symptoms of BOAS. If your dog has mild or intermittent symptoms of BOAS, it can be managed by controlling exercise levels, avoiding stress and hot or humid environments, and keeping your dog in an air-conditioned area during the summer. In the short run, inflamed airway or respiratory distress can be treated with oxygen therapy, Corticosteroids, and nonsteroidal anti-inflammatory drugs (NSAIDs). Bear in mind that medically managing BOAS does not correct your dog’s anatomical abnormalities. Surgery is an option if its anatomical abnormalities impair your dog’s breathing.

For example, stenotic nares can be corrected by removing a wedge of tissue from your pet’s nostrils to improve airflow. Meanwhile, an elongated soft palate can be shortened to a more normal length. Everted laryngeal saccules can be removed to remove any obstruction in the larynx.  The success rate of the surgery is higher when abnormalities correlated with BOAS are corrected. Swelling of the surgical sites may occur and interfere with breathing, at least during the early post-operative period. Don’t worry, your veterinarian will closely monitor your dog after the surgery.


Brachycephalic animals are susceptible to BOAS and can suffer from symptoms ranging from trouble breathing to vomiting. Owners should be careful not to expose their pet to hot or humid conditions. It is also advisable not to transport their pet via air for the sake of its health and safety. If you suspect that your dog has BOAS, consult your veterinarian immediately.