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Brachycephalic Obstructive Airway Syndrome (BOAS)
by admin on May 1st, 2017
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‘BAOS: Too much soft tissue and not enough space’
Brachycephalic breeds are those with squashed up faces! We love them and they are great characters but selective breeding over many generations has encouraged the skull to be progressively shorter over time. However, the amount of soft tissue in the nose and throat has remained the same. These soft tissues include the soft palate, turbinates (cartilage inside the nose) and tongue. These are all crammed into a smaller space. In addition, a lack of underlying nasal bones also causes the nostrils to become very narrow appearing like small slits instead of open holes.
Breathing problems
The crowding of this tissue inside the nose and the back of the throat obstructs airflow through the upper airways. This is why many of these dogs are forced to breathe through their mouth and pant. In an attempt to draw air in through this cramped space many affected dogs will put much more effort into their breathing. This is why if you watch these patients closely you will see them using their abdominal muscles as bellows during breathing. A good analogy for this is comparing how difficult it would be to suck through a very narrow straw compared to a normal one.
The ‘knock-on’ effects of laboured breathing
Unfortunately, the increased effort creates a suction effect in the back of the throat at the opening into the trachea (windpipe). This opening into the windpipe is called the larynx (or voice box in people). It has a tough cartilage frame which keeps it open wide. However, constant suction in this region over a period of months can cause it to fold inwards further narrowing the airway and causing serious breathing difficulty. This secondary problem is called laryngeal collapse.
What about the nose?
The nose is an important part of the anatomy and it functions to warm and humidify the air before it is inhaled into the lungs. It is a crucial part of how dogs maintain a normal body temperature. If affected dogs can’t breathe through their nose then this significantly affects their ability to thermoregulate and explains why they have poor heat tolerance. Of course, it is no surprise that many patients present with breathing problems in the summer months.
What are the clinical signs of Brachycephalic Obstructive Airway Syndrome (BOAS)?
The main clinical signs in approximately increasing the order of concern include:
- Loud snoring during sleep
- Noisy breathing (especially during excitement or exercise)
- Panting
- Poor ability to exercise
- Heat intolerance
- Choking on food
- Regurgitating
- Laboured breathing
- Development of blue gums or tongue
- Fainting
Aren’t some of these signs just ‘Normal’ for the breeds?
Yes and no. The problem is that a large number of brachycephalic dogs show the signs at the milder end of the above spectrum and our tolerance of what is normal for these breeds has become skewed. We frequently see patients coming into our clinic for unrelated problems with marked breathing difficulty. When questioned their owners often state that they consider these signs as normal for the breed. They often add that most other dogs of the same breed that they come across on walks sound and react the same which reinforces this notion! Therefore it is important that we get the message across that these signs are abnormal and if your dog is displaying some of them then a veterinary opinion should be sought.
Be proactive!
A proactive approach is beneficial as there are many surgical treatments which can be carried out that will help these patients breathe. Although these treatments will not produce a ‘normal’ airway it will invariably improve airflow, thus improving their quality of life and ability to exercise. The latter is particularly important as obesity makes this problem significantly worse. Intervention early in life can reduce the amount of suction at the back of the throat and therefore reduce or delay the development of secondary laryngeal collapse for which there are limited options available.
See the excellent new film on BAOS by the Kennel Club on Youtube entitled ‘Dog Health: What Is Brachycephalic Obstructive Airway Syndrome?’
