Brachycephalic obstructive airway syndrome (BOAS)

i canis

Contributor(s):

Lynelle Johnson

Jill Sammarco

Gert ter Haar

Nai-Chieh Liu

Synonym(s): Brachycephalic upper airway obstruction syndrome, BAOS, BAS, BUAOS

Introduction

Cause: congenital shortening of the bones of the skull when the soft tissues within the upper airway do not reduce in size proportionally; maldevelopment of the airway cartilages.
Signs: excessive panting, dyspnea, stertorous and stridorous breathing, respiratory effort, sleep-disordered breathing, exercise and heat intolerance, regurgitation/vomiting, cyanosis and collapse.
Diagnosis: breed, clinical signs, respiratory function tests, diagnostic imaging, endoscopic examination.
Treatment: medical treatment and surgical widening of the airways where possible.
Prognosis: good in mild-moderate cases with surgery.
Print off the owner factsheet on Brachycephalic upper airway obstruction syndrome (BUAOS) Brachycephalic upper airway obstruction syndrome (BUAOS) to give to your client.

Obesity Obesity.
Hot weather.
Exercise.
Excitement.
Stress.
Concurrent cardiac or pulmonary diseases.
Concurrent or secondary gastro-intestinal diseases with gastro-esophageal reflux.

Airflow through airways is impeded due to abnormal anatomy → noisy breathing and inability to take on board sufficient oxygen to meet increased demands imposed by exercise.
Restricted airflow → increased inspiratory effort → increased negative pressure within the upper airways leads to a high intrathoracic negative pressure which in turn leads to eversion of laryngeal saccules and airway collapse as well as a sliding hiatal hernia Hiatal hernia of the stomach.
Increased respiratory effort may → upper airway edema → further obstruction to airflow. Regurgitation Regurgitation leads to acid reflux and increase in pharyngeal and laryngeal inflammation and thus a vicious cycle is set in motion.
Impeded airflow prevents adequate heat loss through panting so animals rapidly become hyperthermic Hyperthermia in hot weather, following exercise or during stress.
If the respiratory vicious cycle is left untreated, the dog may develop pulmonary edema, reduced arterial oxygen content, hypertension, and right-sided heart failure.

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