Brachycephalic Obstructive Airway Syndrome (BOAS)

What is Brachycephalic Obstructive Airway Syndrome (BOAS)?

BOAS (Brachycephalic Obstructive Airway Syndrome) is the name given to the effects of the passage of air through the upper airways of dogs with shortened heads/flat faces.  The soft tissue structures within the upper airways have not adapted structurally with the shortening of the skull and therefore are squashed and packed within the smaller bony structures and can block the airways. 

Animals suffering from BOAS can struggle to breathe during exercise and warm weather and may suffer collapse due to the lack of air.  They will usually make snorting noises and snore and often have their tongues hanging out.

BOAS is a lifelong and often progressive disorder that can affect an animal’s ability to breathe, exercise, eat, play and sleep.  Extremely brachycephalic dogs have a shorter life span compared to those with less extreme brachycephaly or non-brachycephalic dogs

Which breeds are affected?

The most distinctive feature of these breeds is their shorter and wider skull and shorter muzzle.  Any breed of dog or cat with a brachycephalic head conformation can be affected, the following list gives an example of the most common breeds affected,  this list is not exhaustive. 

Dogs:

• Bulldog
• French Bulldog
• Pug
• Boxer
• Boston Terrier
• Cavalier King Charles Spaniel
• Lhasa Apso
• Shih Tzu
• Japanese Chin
• Pekingese

Cats:

• Persian
• Himalayan
• Burmese
• British Shorthaired

Why do these animals have problems?

The main areas of concern in these animals are:

• Narrowed nostrils/stenotic nares – the narrowing of the nostrils may be so significant that they only resemble a slit meaning airflow is greatly reduced.
• Overlong/elongated soft palate – when this is too large it may partly obstruct the windpipe when the dog is taking a breath which reduces the air they can take in and results in a snorting sound.
• Enlarged tongue – Many of these animals have an enlarged tongue due to the changes in their skull from selective breeding.  This creates an additional barrier to the airflow getting to their lungs.
• Tracheal hypoplasia (reduced size of the trachea or windpipe meaning it is too small for the size of animal) – this will be due to not developing properly, which means reduced air entering the lungs.

Unfortunately, the extra effort required to breathe eventually results in secondary problems, since the airway is not adapted to cope with the turbulence and increased negative pressures which develop.

These secondary effects include:

• Tracheal collapse – The larynx or voice box can become damaged by chronic stress to the cartilage from working too hard to breathe. Laryngeal collapse leads to further blockage of the airway and therefore trouble breathing.
• Everted laryngeal saccules –  In normal anatomy there are two small pockets (saccules) in the back of the throat. In brachycephalic dogs, there is an increased effort to breathe, in turn this effort can cause the saccules to turn inside out and further block the airway.
• Tonsillar eversion and hypertrophy. The tonsils usually lie in shallow recesses towards the back of the mouth. The increased negative pressures can cause them to enlarge and protrude into the back of the mouth, further narrowing the airway.
• Pharyngeal muscle hypertrophy. The pharynx is the term used to describe the area at the back of the mouth and entrance to the larynx. These muscles can become enlarged (hypertrophied) due to the altered pressures in the upper airway.
• Acid reflux from the stomach into the oesophagus (food pipe).  The chronic increase in thoracic airway pressure draws the stomach into the chest, causing gastroesophageal reflux.  This can result in inflammation of the oesophagus and sometimes in ulceration of the stomach. Severe cases may suffer from a hiatal hernia, this is when part of the stomach herniates into the chest cavity during breathing.

How is BOAS diagnosed?

The diagnosis is made based on a combination of factors including the breed of dog, symptoms and our Vets physical examination findings.  When carrying out a physical examination our Vet will assess your pet’s anatomy (some heads are shorter than others) and your pet’s behaviour in certain circumstances, we will also perform a trotting exercise tolerance test.

Most brachycephalic animals will experience a degree of upper airway obstruction, usually evident as snorting or snoring noises. The decision is for the pet owner and our Veterinary Surgeon to decide whether your pet is experiencing a significant level of signs to mean surgery is indicated.  The discussion will involve discussing how your pet copes with exercise or in warm conditions and also any likely susceptibility to secondary deterioration within the airway.  Videos of your pet at home will assist in making this decision.

Unfortunately, only the nares (nostrils) can be properly assessed without the requirement for a general anaesthetic.  Therefore, initially the diagnosis is based on the Veterinary Surgeon’s overall assessment but will require further investigation under general anaesthetic in order to confirm the diagnosis.  In some instances a CT scan or other further investigations may be appropriate before a surgery recommendation is made.

How is BOAS treated?

BOAS is not curable, however upper airway corrective surgery can provide a better quality of life.  Revisional surgery may be required in some severely affected dogs.

General anaesthesia in brachycephalic dogs can be associated with increased risk, particularly during the anaesthesia induction and recovery phases.

Many Veterinary Surgeons choose to refer these cases to a more experienced surgeon in order to carry out an assessment of the airway under general anaesthesia, with the advantage that surgical treatment can be carried out under the same anaesthetic and therefore reduce the risks during the recovery phase caused by repeat anaesthetics.

Here at The Meopham Veterinary Hospital our surgeons perform this procedure on a regular basis and accept referrals in this discipline.  We have dedicated, on site 24 hour care at the Hospital and these patients will have a nurse with them at all times to ensure their recovery is as safe as possible.  We have advanced patient care monitoring equipment and are RCVS accredited to the highest level.

All BOAS procedures are carried out by Dr Martin Hobbs, Dr Rupert Davenport or Dr Penny Barnard-Bosma.  They all continued with post graduate study and have each gained further accredited certificates, one of those being in small animal surgery.  With 57 years of combined Veterinary experience please rest assured that your pet is in experienced hands.

For further information please do not hesitate in contacting us at referrals@meophamvets.co.uk or 01474 815333.

We are a family owned, independent RCVS accredited Small Animal Hospital.  We are situated in North Kent and are easily accessible from both the M20 and the A2.  Conveniently located on the A227 only 15 minutes from Gravesend and less than 20minutes from Bluewater.

We regularly accept referrals from all over the South East including Kent, Essex, Surrey, Sussex and the London Boroughs.