What does brachycephalic mean?
The term brachycephalic comes from the Greek meaning ‘short’ and cephalic meaning ‘head’ i.e. brachycephalic animals are those with flat faces and short snouts.
What is Brachycephalic Obstructive Airway Syndrome (BOAS)?
Brachycephalic obstructive airway syndrome, commonly referred to as BOAS, is the term given to the effects that the shortened head has on the passage of air through the upper airways. The signs can vary in severity from mild snoring or snorting noises to more severe breathing problems.
Animals suffering from clinically significant BOAS can struggle to breathe during exercise and may suffer collapse due to lack of air. The reliance of dogs on panting to cool themselves also makes animals suffering from BOAS very susceptible to overheating and developing potentially serious breathing difficulties in hot conditions.
What breeds are affected?
Brachycephalic breeds include those breeds of dog that have an obvious, characteristic short or squashed nose appearance. There are also several cat breeds that are also brachycephalic. Common breeds include:
Dogs:
- English Bulldog
- French Bulldog
- Dogue de Bordeaux
- Boxer
- Pug
- Cavalier King Charles Spaniel
- Lhasa Apso
- Shih Tsu
- Pekingese
Cats:
- Persian
- Himalayan
Why do these animals have problems?
There are four main areas of concern in these animals:
- Narrow nostrils (nares)
- Overlong palate
- Secondary effects such as collapse of the larynx (voice box)
- Tracheal hypoplasia (the trachea or windpipe is too small for the size of animal – almost exclusively encountered in the English Bulldog breed)
Whilst dogs are commonly presented with problems resulting from BOAS, cats are rarely presented for treatment. This may be because they have a more sedentary lifestyle compared to dogs. Most cats only present for treatment for narrowed nostrils.
Narrowed nostrils can dramatically increase the resistance to air flow into the nose. This, combined with the tendency for the cartilage supports of the nares to collapse during inspiration, requires a much larger effort than normal in order to breathe.
An overlong soft palate can partially obstruct air flow into the trachea (windpipe) and also cause turbulent airflow in the area of the larynx (voicebox). Both of these effects further increase the effort required for an pet to breathe in, and can cause significant inflammation of the upper airway.
Unfortunately, the extra effort required to breathe in eventually results in secondary problems, since the airway is not adapted to cope with the turbulence and increased negative pressures which develop.
How is BOAS diagnosed?
When carrying out a physical examination, your primary care vet will assess your dog or cat’s anatomy (some heads are shorter than others) and your pet’s behaviour in certain circumstances.
Most brachycephalic animals will experience a degree of upper airway obstruction, usually evident as snorting or snoring noises. The key is for you and your veterinary surgeon to decide whether your pet is experiencing a significant level or showing an anatomical conformation that may indicate problems. The discussion will involve how your pet copes with exercise or warm conditions and also any likely susceptibility to secondary deterioration within the airway.
Unfortunately, only the nares (nostrils) can be properly assessed without the requirement for a general anaesthetic. Initially therefore, the diagnosis is based on the veterinary surgeon’s overall assessment but will require further investigation to confirm the diagnosis.
How is BOAS investigated by the veterinary surgeon?
There are a number of tests that may be required, depending on the findings of the initial physical examination. These can include blood tests, cardiac (heart) assessment and chest X-rays. However, full airway assessment will require an anaesthetic.
General anaesthesia in brachycephalic dogs can be associated with increased risk, particularly during the induction and recovery phases.
Many primary care vets choose to refer these cases to an experienced surgeon 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.
The surgeon may use an endoscope (small camera) to examine the oesophagus for signs of gastric reflux.
What treatment options are available?
Stenotic Nares (narrowed nostrils)
Removal of a section of the cartilage of the front of the nose or a section of skin next to the nose can improve the airflow through the nares.
Overlong Soft Palate
The excess length of the soft palate can be reduced by surgery in order to reduce the interference with air flow into the larynx (voice box).
Laryngeal Collapse
Early laryngeal collapse can sometimes be improved by removal of some of the tissue that is slowing airflow. The surgeon will assess the larynx (voice box) and decide whether additional surgery in this area is appropriate or likely to be beneficial. Sometimes, this additional procedure may need to be carried out at a later date.
Severe (Grade 3) collapse is unlikely to benefit greatly from a minor procedure and may require a permanent tracheostomy (breathing hole in the neck), or can sometimes be temporarily improved with a tieback procedure (see laryngeal paralysis information sheet).
Everted tonsils
Some cases may benefit from tonsillectomy (removal of the tonsils). The decision on whether this is appropriate is made at the time of assessment and surgery.
Acid reflux
Treatment for gastric reflux usually involves regular medication, rather like one might take for heartburn.
Hiatal Hernia
In general, conservative management is initially employed in cases suffering from displacement of a section of the stomach into the chest, although some cases do require surgical treatment.
Weight management
The lifestyle of many of these patients can predisposed them to obesity. Weight loss can dramatically improve the airflow through the pharynx and neck and MUST form part of the treatment protocol in overweight patients.
What is the outlook following treatment?
Most dogs suffering from signs of BOAS that receive prompt appropriate treatment can experience a significant improvement in exercise tolerance and ease of breathing. However, due to the fact that the surgeon can never create a completely normal airway for brachycephalic animals, they remain susceptible to heat stress and many are unlikely to be able to exercise to a level that one might expect from animals with normal head conformation.
It is generally hoped that surgery to the nares, soft palate and the larynx will slow the progression of laryngeal collapse (voice box collapse) by improving the airflow and reducing the negative pressures developed during respiration. Early surgery, carried out before the laryngeal collapse has become severe, should maximise the benefit from surgery and minimise the risks of significant laryngeal collapse later in life.
Many dogs do not experience significant further deterioration in the larynx during their lifetime and therefore never require further surgery. Unfortunately, despite treatment, laryngeal collapse can reach a critical level in some cases and may require further surgery at some point in the future.
Despite the many precautions taken by veterinary surgeons in assessment and treatment of these patients, the risk of the general anaesthetic and surgery to the airway can never be eliminated. The surgeons and anaesthetists at Cave are acutely aware of the special needs of brachycephalic patients undergoing general anaesthesia and airway surgery.
Hypoplastic trachea (small windpipe) cannot be treated and these dogs are often severely affected by the impairment to airflow associated with this condition.
