Brachycephalic Obstructive Airway Syndrome (BOAS)
BOAS is a condition that all short faced dogs have to some degree. It manifests as increased noise when breathing during excitement, exercise, humid weather and snoring when sleeping. Affected dogs may pant excessively, gag, cough, regurgitate, vomit, aspirate and in severe cases collapse, asphyxiate and die. The basic problem is there are anatomic structures that are too big trying to fit into a throat that does not have enough space. This creates a bottleneck vacuum which sucks surrounding tissues into the larynx.
The solution is to move and remove those structures that can be done safely and without interfering with ongoing function. Recent data from Dr Moses’ group in Queensland indicates that complication risk increases in middle age 4-5 years and surgery should ideally be performed well before this.BrachyAirwayReport AVJ
Stenotic nares or nostrils
Some dogs are born with very narrow nostril openings and some narrow over time. Surgery involves removing a triangular wedge from the bottom of each nostril fold and opening it to the side in similar fashion to opening a curtain. Sutures are placed to hold this repair in position until it has healed. Our current techniques uses sutures that do not need to be removed but will take 8 weeks to dissolve.
Elongated and enlarged soft palate
The soft palate is the membrane at the back of the the mouth that separates the nasal passages from the larynx. Enlargement and elongation of the soft palate is the main cause of airway obstruction in most dogs. Surgery involves a number of techniques to shorten, stretch out and/or thin this membrane to stop it blocking airflow from the nose the larynx.
Enlarged tonsils
The tonsils sit at either side at the roof of the mouth. They can enlarge to almost touching from side to side and can be removed to provide more air space.
Everted laryngeal saccules
The laryngeal saccules are inverted membranes that allow the vocal cords to move to close. They too can be sucked into the airway and present the second most common reason for airway obstruction. They can be surgically removed to improve vocal cord movement.
The swollen soft palate,tonsils and laryngeal saccules are composed of water and connective tissue. After removal they dehydrate and shrink rapidly.
What we have learnt regarding BOAS surgery and what is on the horizon
The surgeries described above are the most common performed and for the vast majority of dogs, this combination will provide significant long-term benefit. In addition to these surgeries, there have been investigations into laser assisted turbinectomy (LATE) whereby a laser beam is used to reduce the internal scroll membrane and cartilage mass within the nasal passages to create more airspace. The evidence suggests that this procedure may help some dogs if performed early in the disease process but the drawback is cost and availability of the equipment. There has been recent experimental work done in reducing the size of the tongue so that it sits lower in the mouth and occupies less space at the back of the throat. It is a surgery that has been performed in extreme cases and the medium to long-term outcomes are still to be determined.
After reviewing the last 900 cases, as of October 2021, that we have performed, the following observations have been made;
Surgery time varies between 25 to 40 minutes to complete nostril surgery, tonsillectomy, soft palate surgery and resection of the everted laryngeal cycles.
We have had one fatality relating to post-operative reflux and aspiration despite adequate fasting, appropriate medication to reduce vomiting and appropriate monitoring. Our protocol includes the use of metoclopramide or maropitant pre-operatively and all patients are physically held by our nursing staff during recovery. We have found that our nurses are very good at feeling if a dog is about to regurgitate or vomit and simply elevate their hindquarters so that whatever comes out will run down.
All patients receive one week of pre-medication and one week of post-medication with prednisolone and doxycycline. Firstly, after one week many dogs will show an obvious improvement with medication as it reduces much of the swelling that may be present in the soft palate. Secondly, the reduction in swelling makes the surgical landmarks easy to identify. Thirdly, we do not get the same degree of post-operative swelling. This means we have better recoveries and greatly reduce need to keep dogs in hospital. Most dogs will take between one and two hours to sufficiently recover from anaesthesia for us to be happy considering discharge from hospital. We have not had to insert a tracheostomy tube to facilitate breathing in the last two decades!
For those dogs undergoing corrective surgery prior to skeletal maturity, almost one in four will require a revisionary surgery in the future. This is because membranes in and around the soft palate will continue to grow and stretch. For those dogs undergoing corrective surgery after skeletal maturity the requirement for a revisionary surgery reduces to almost one in 50 dogs.
Our pain relief protocol includes the use of local anaesthetic – 2% lignocaine and adrenaline injected into the nose, base of the tonsils, side wall of the soft palate and into the everted laryngeal saccules. We have had two French Bulldogs show adverse reactions to lignocaine and adrenaline requiring the administration of an antidote, stopping surgery, allowing recovery and coming back to repeat the surgery four weeks later. In neither case could this reaction be predicted but it is easy to detect with ECG monitoring and simple to manage.
One in five French Bulldogs will be completely silent after surgery and will lose the soft grunt that they typically make in addition to no snoring at no increased noise with exercise. Ironically, we have had owners comment with disappointment when this happens because they did not understand that the breathing noise and respiratory difficulties coincide. Consistent with previous studies, the post-operative silence is more likely to occur in those dogs with longer noses, longer bodies and longer legs.