Brachycephalic obstructive airway syndrome (BOAS), also known as brachycephalic airway obstructive syndrome (BAOS), brachycephalic airway syndrome (BAS), and brachycephalic syndrome (BS), is a pathological condition affecting short nosed dogs and cats which can lead to severe respiratory distress. There are four different anatomical abnormalities that contribute to the disease, all of which occur more commonly in brachycephalic breeds: an elongated soft palate, stenotic nares, a hypoplastic trachea, and everted laryngeal saccules. Because all of these components make it more difficult to breathe in situations of exercise, stress, or heat, an animal with these abnormalities may be unable to take deep or fast enough breaths to blow off carbon dioxide. This leads to distress and further increases respiratory rate and heart rate, creating a vicious cycle that can quickly lead to a life-threatening situation.
