Brachycephalic syndrome is a group of conditions that hinder airflow through the upper respiratory tract (nose and larynx) of short-nosed or brachycephalic dogs such as Boston Terriers, Bulldogs and Pekingnese. These dogs' compressed faces have shortened bones but not shortened soft tissue. The excess soft tissue leads to blockages in airway. Stenotic nares, or pinched nostrils, overly long soft palates and everted laryngeal saccules are the most common conditions encountered in dogs with BAOS.

Even when the condition is present at birth, clinical signs generally don’t begin until early middle-age. Your dog will have difficulty breathing and the breathing will be abnormally loud. Your dog will likely snort and snore as well. These breathing difficulties will worsen in hot weather and when your dog exercises. The breathing difficulties will also generally become worse as your dog ages.