Glossary

Brachycephalic obstructive airway syndrome

A set of airway abnormalities in flat-faced breeds that make breathing hard, causing noisy breathing, poor heat tolerance and collapse.

Also called: BOAS, brachycephalic syndrome, flat-faced dog breathing problems, brachycephalic airway syndrome

Brachycephalic means short-skulled. The flat faces of breeds such as the Pug, French Bulldog and Bulldog pack the same airway into less space. Typical BOAS features include narrow nostrils, an overlong soft palate, a narrow windpipe and swollen tissue in the throat.

The result is snoring, snorting, noisy breathing even at rest, gagging, trouble with exercise and heat, and sometimes collapse or blue-tinged gums. These dogs overheat quickly because panting is how they cool down. Owners often accept the noise as normal for the breed, but it is not.

Vets grade the severity, and surgery can help some dogs. Flat-faced dogs also carry extra risk under anesthesia. Ask a veterinarian to assess breathing before a puppy is bought and at every wellness exam.

Last reviewed November 8, 2026

In the index now

Related terms

Heatstroke A dangerous rise in body temperature, from about 104 F up, when a dog cannot cool itself, and a true emergency. Anesthesia A medically induced, controlled loss of consciousness for surgery, dental cleaning or imaging, with monitoring throughout.