EDITOR'S NOTE: Surgery STAT is a collaborative column between the American College of Veterinary Surgeons (ACVS) and DVM Newsmagazine.
Brachycephalic airway syndrome is described in dogs and cats that have brachycephalic conformation (a short, wide head). The
primary components of the syndrome are stenotic nares, an elongated soft palate and a hypoplastic trachea (most often seen
in English bulldogs). All these features can be present, or the presence and severity of each component can vary. The result
is altered airway pressures.
Syndrome effects
The smaller breathing lumens make for an increased respiratory effort, which is most apparent on inspiration. Fluid (or air)
flow through a tube is described by Poiseuille's law that states that, in regard to the radius of a tube's lumen, flow is
directly related to the radius raised to the fourth power. So small changes in airway size create vast changes in flow—especially
in small patients with small airways. Over time, the increased work of breathing causes the secondary components of the syndrome—eversion
of the laryngeal saccules and laryngeal collapse.
The increased resistance to airway pressure creates more work for the patient to move air in and out of its lungs. This creates
problems during exertion or when exposed to high ambient temperatures when panting is needed to cool the body. These scenarios
can create an obstructive airway crisis, hyperthermia or both. As the disease progresses and secondary changes occur, a crisis
can occur with minimal stress or exertion. Chronic hypoxia creates pulmonary vasoconstriction and eventually pulmonary hypertension.
Commonly affected breeds are English bulldogs, French bulldogs, pugs, Boston Terriers, Pekingese, Pomeranians, Shih Tzus and
boxers. Hypoplasia of the trachea is most common in English bulldogs and is likely responsible for a worse prognosis in this
breed.
Most surgeons think that to prevent the development of the secondary components of brachycephalic airway syndrome, the patients
should undergo surgery at a young age since there are reports of dogs as young as 6 months of age with laryngeal collapse.
Performing corrective procedures is often done concurrently with spaying or neutering. Each patient needs to be assessed on
an individual basis to determine which procedures are indicated.
Patient assessment
During the initial examination, evaluate patients for evidence of dyspnea. If open-mouth breathing alleviates dyspnea, the
obstruction is likely nasal in origin. If dyspnea persists despite open-mouth breathing, soft palate and laryngeal lesions
are likely present.
Preoxygenate animals before anesthetic induction. Examine the nares to determine whether the wing of the nostril impinges
on the nares. First examine the nares while the patient is awake and then after anesthetic induction. During awake inspiration,
animals with severely stenotic nares can be seen to suck the wing medially.
Upon induction, examine the palate and larynx. The length of the palate is deemed elongated when it comes past the level of
epiglottis. Evaluate larynx function and look for evidence of collapse or dysfunction. Perform a thorough evaluation so that
treatment can be tailored for each patient's needs.
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