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Brachycephalic Obstructive Airway Syndrome (BOAS)

Updated: Nov 30, 2023

Brachycephalic Obstructive Airway Syndrome (BOAS) is a condition that causes difficulty breathing, exercising, and controlling body temperature. It can occur in any brachycephalic dog and is caused by the unique combination of ‘squishy’ features that the dog may have (a short nose, small nostrils and sinuses, large tongue and tonsils, narrow windpipe and wide neck). BOAS episodes can be very dangerous, resulting in extreme panting, overheating and possibly collapse. BOAS episodes are a veterinary emergency, and if the dog does not recover swiftly, they can even be fatal.

French Bulldog face with big tongue

Over time, as brachy dogs have been bred for shorter and shorter faces, their skulls have reduced in length dramatically. However, we now know that the soft tissues of the face such as the tongue, soft palate and tonsils, have not shrunk accordingly. These are now taking up too much room in a dramatically shortened skull, making air exchange much harder.

Dogs cool themselves down by panting, and by exchanging air in the sinuses and nasal passages on the inside of the nose. For a brachy dog, with tiny nostrils and a hugely reduced space inside the nose, this process is dramatically compromised, which can make them very predisposed to heat stroke.

Brachy windpipes have become narrower over time, and the opening to this windpipe is more likely to get blocked by excessive tissue in the way (big tonsils, soft palate and tongue). When these dogs get hot, their throats can swell much more than other dogs, potentially leading to a terrifying combination of not being able to breathe air in, the windpipe being blocked, and gradually getting hotter and hotter until they collapse. When the body gets deprived of oxygen like this, it can go into organ failure. This is what happens when dogs die of BOAS.

brown bulldog sitting on grass

Signs of BOAS to watch out for in your dog:

  • Excessive panting, snoring, snorting or gagging (excessive meaning anything that is more than average for your dog, or going on for longer than is usual for your dog after excitement or exercise)

  • Anything that looks like ‘difficulty breathing’

  • Drooling more than normal

  • Wobbliness or weakness

  • Anything that looks like collapse or fainting

  • Bright red, blue or purple tinged gums, tongue or lips (this one is an EMERGENCY – get straight to your closest vet!) Nb. Pink or pale pink is the normal colour for the tongue and gums, as shown in this photo ^^^

BOAS is particularly prevalent in three breeds: the French Bulldog, British Bulldog and Pug:

Whilst many dog breeds have a degree of brachycephaly, these three are known as the ‘extremely brachycephalic’ breeds as they have the most extreme shortening of the skull. They are the three most common breeds seen presenting to vets for BOAS treatment and surgery. Miniature Bulldogs and Australian Bulldogs, being derived from similar genetics to the British Bulldog, are also susceptible. The Boston Terrier is one of the next most brachycephalic breeds and BOAS can also be a concern for them.

RightPaw breeders of brachy breeds must be aware of BOAS and be actively reducing their incidence of this disease in their kennel. They will never breed from a dog who has ever had a clinical episode of BOAS and are encouraged to test their breeding dogs for exercise intolerance, nostril width and length of nose to try to reduce the incidence of this disease in their puppies.

Click here for more details: RightPaw Brachycephalic Breeding Policy


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