Pinched nostrils, otherwise known as stenotic nares, occur when the nostrils of certain breeds of dogs are smaller than normal, resulting in a smaller passageway to the lungs with a markedly increased resistance to airflow. Though it can theoretically affect any breed, dogs with short, wide heads such as bulldogs, pekingnese, and pugs are far and away the most frequent sufferers.
In addition to the obvious problems presented by this disease, it should also be known that pinched nostrils are very often accompanied by other abnormalities such as an overlong soft palate, and a tendency for the larynx to collapse due to strain. [...]
The medical term for pinched nostrils is stenotic nares and it is a common problem in many of the brachycephalic or pug-nosed dogs. These breeds seem to have a huge list of respiratory problems that can develop over time due to their short head formation and the compact nature of the respiratory system. Stenotic nares in themselves may not be problematic for the dog unless there are other complications that make breathing difficult for the pet.
The most common breeds affected by stenotic nares include Pugs, Boston Terriers, Pekingese, English Bulldogs, Boxers and Shih Tzus. These dogs are born with cartilage malformations in the nose that limit or restrict the opening of the nostril, slightly to greatly reducing the airflow through the nose. [...]