Hypoplastic Trachea

One of our biggest concerns with brachycephalic breeds, especially British Bulldogs that are severely over represented for this condition, is hypoplastic trachea. Very simply, this is a trachea (windpipe) that is narrower than normal.

Here are the breed averages:

• Normal nose dogs 0.20 (or 20% the diameter of the thoracic inlet)
• Brachycephalics generally 0.17
• British Bulldogs 0.13

 

So generally speaking, all brachycephalics have a 15% reduction in the size of their trachea, and British Bulldogs in particular have a 35% reduction in the size of their trachea. Here’s the real problem with this – these breeds already struggle for oxygen for the following reasons:

• Short noses
• Crowded intranasal turbinates
• Enlarged tongues and tonsils
• Swollen laryngeal saccules further blocking their small tracheas
• Elongated soft palates entering the larynx
• Stenotic nares

Adding a significant hypoplastic trachea to the above list of restrictions, is a major problem.

The Veterinary Problem

We remain concerned the veterinary profession, generally speaking, is uneducated with regards to this concern. We have seen many cases of moderate to significant hypoplastic tracheas that have been completely missed by vets (that have a reputation for experience with bulldogs), and even specialists.

Melbourne Bulldog Clinic is calling for the University curriculum to address this problem (along with many other misunderstandings of these breeds), at the student level to improve the veterinary profession service to brachycephalic owners. In the meantime, we hope to educate both owners and veterinarians with our thoughts and recommendations from our experiences, and welcome open discussion on this topic.

The non-diagnosis of this problem by many vets leads to the following concerns:

• These dogs when young, have significant bouts of reflux pharyngitis, often misdiagnosed as aspiration pneumonia and unnecessarily hospitalised for days.
• There is significant increased sedation and anaesthesia risk in the dogs, especially when young, that needs to be explained and accepted
• We feel these dogs should wait until 10 months of age before anaesthesia if possible. If they are struggling with breathing and non-responsive to medical management, then the risk of early anaesthesia and airway improvement needs to be understood and accepted.

Diagnosis of Hypoplastic Trachea

We feel the following guidelines should be considered:

• With risk breeds if excessive congestion, snoring, panting and exercise concerns exists, a single lateral x-ray should be taken to rule hypoplastic trachea in or out.
• Although our clinic generally sedates all dogs for x-rays for both accuracy and staff safety, these dogs do carry higher risk with sedation – especially if there is a significant to severe concern, that must be communicated and understood. Hence, we choose not to sedate if possible, and just quickly take an X-ray in the consultation to diagnose. If this is not possible then we will risk a mild sedation, even though that risk is still very low.
• There are two ways to measure the trachea. Either visually by guesstimating the degree of concern compared with a normal trachea, or officially by measuring the thoracic inlet to trachea diameter ratio. There is so much variation with the official measurement, and so much vet to vet subjectivity over how to measure these that we actually prefer the first method, (but we also do an official measurement). But depending on who does that official measurement and exactly where they take their measurements from, we view these measurements with scepticism.
• We start by simply assessing whether the trachea is hypoplastic then if it is, grouping it into on of the following estimates:

1. Mild 0.14 to 0.16

2. Moderate 0.12 to 0.14

3. Significant 0.08 to 0.12

4. Severe Less than 0.08

This diagram shows how to correctly measure the trachea diameter as a ratio of the thoracic inlet. The width of the trachea, in this case 1.14 cm, is divided by the thoracic inlet distance, in this case 5.22cm. This gives a trachea ratio of 0.218 – slightly above the average for a normal dogs trachea.

But far more importantly than the maths, just look at the trachea. Look how wide it should be in a normal dog.

Important Management Considerations

The ratio does seem to improve with age up to 10-12 months in many individuals, but this is not a given in all dogs. This fact is why we feel anaesthetic risk will be lower at that age if the ratio has improved, hence we prefer to manage breathing restrictions medically in these patients, rather than going straight to surgery. The management of hypoplastic trachea includes the following:

1. Steroids at 0.2mg/kg dexamethasone for 24 hours, to then continue prednisolone at 1mg/kg daily for 3-5 days only in acute cases. (Just start with oral prednisolone in less acute cases)

2. Metoclopromide at 5-10mg 2x daily for 7-15 days. (This can be adjusted according to weight etc.)

3. Omeprazole at 10-20mg once daily ongoing if a good response is achieved, but again this can be adjusted as appropriate.

 

A few points for vets on the above triple treatment to manage these cases:

• If there is not significant improvement after 24 hours of starting steroids, or indeed if the patient is worse, then stop steroids and consider radiology in case true aspiration pneumonia is of concern. Almost all improve significantly, but just keep this safety check in mind.
• Although we only really use steroids for short “recover” bursts to get quick control of excessive gagging, coughing, vomiting, increased breathing effort, we occasional may consider a low 0.25mg/kg every second day dose for weeks to a few months if really needed to control signs well. But ideally if this is needed, we may recommend an initial early surgery.
• Omeprazole can be used two times daily and in higher doses, but about 10-20% of cases actually respond poorly to Losec, potentially worsening vomiting or at least having no effect. So monitor and manipulate as appropriate.

Managing these cases as per the above is preferential to surgery if it is working really well, but is also a bit of an artform rather than an exact science given the different responses different individuals can have to the various medications. Experience helps. If not managing quickly and well with a balancing of the triple treatment, then for early surgery we recommend consider the following:

• Explain the increased risk of both death, and potential need for an emergency or elective tracheotomy with the smaller trachea ratio.
• We feel removing tonsils, saccules if everted (highly likely) and nares widening gives an excellent chance of relief, and has less chance of post-surgical swelling and complications than palate surgery as a first step. However, if the palate is very significant then potentially addressing this at that time may be less of a risk that not. A judgement call needs to be made with experienced examination, but we tend to recommend everything but the palate first up as an early surgery.
• Do explain the palate is still growing hence will highly likely need another surgery at 12-18 months if addressing this aspect on the first surgery.

Reflux Pharyngitis and the (mis)diagnosis of Aspiration Pneumonia

Although this is common in brachycephalics, we feel hypoplastic trachea dogs in the first 2-8 months are severely over represented for the potential misdiagnosis of aspiration pneumonia, given their increased breathing concerns.

Visit our link on reflux pharyngytis for a complete understanding of this condition, which significantly overlaps with hypoplastic trachea.

The Welfare Issue

Melbourne Bulldog Clinic remains very concerned at the lack of action taken by breeders, breed clubs, registries and mainly the Veterinary profession, RSPCA and AVA over no set guidelines for better breeding. Learn more about our general concerns and solution to the problem, but also keep the following in mind for hypoplastic trachea specifically:

If your dog has been diagnosed with this horrific life sentence, understand it’s due to the lack of interest and action from all of the above. Please be an advocate for these breeds and demand breeders screen and exclude any dog with a tracheal ratio of less than 0.16.

As an example of how bad hypoplastic tracheas can get, this is an example of three severe cases ranging from 0.07 to 0.08.

Manty vets recommend euthanasia with such severe hypoplastic tracheas, however all three of these dogs survived airway corrective surgery at Melbourne Bulldog Clinic to at least make as much room as possible so that they had less restrictions to contend with – two of them going on to live a reasonably normal life.