Brachycephalic Syndrome
Some animals, such as the pug, are bred to have shortened skulls, resulting in shortened jaws and a flat faced appearance. These types of animals with flat faces are called brachycephalic breeds. Many people think this looks great on their animals, but what they do not know is that by breeding for a shortened upper jaw they shorten pieces of the animal that could seriously compromise the animal’s health. A dog or cat with a flat face is usually born with brachycephalic syndrome and other related health issues.
Brachycephalic syndrome usually affects different areas of the respiratory system, but can also affect the jaw, eyes, teeth, immune system, and joint structure of the animal’s body. Most animals do not have all of the symptoms, but they usually are affected by one or more. The most common anatomical features that lead to the respiratory difficulties typical of these breeds include an elongated and fleshy soft palate, and narrowed nostrils, referred to as stenotic nares. Many affected animals also have changes to the larynx and a relatively small trachea.
With stenotic nares, the nostrils are narrowed. When an animal breaths, the sides of the nose cave in slightly, due to the suction of the air moving through the nasal passage. In an animal with a small nasal opening, the sides of the nose act as flap-like valves that even a slight respiratory effort pulls tightly shut. You can see and hear the difference in breathing between an animal with open nares and one with stenotic nares. The harder the animal tries to breathe, the more tightly the nares clamp shut, and the more the walls of the airway are pulled inward. This condition can be surgically corrected, and involves the widening of the nasal openings. 
 Another problem with these breeds is that animals with long muzzles have large nasal chambers with thin, curved bony shelves called turbinates projecting into the chambers from the sides. These structures help increase the surface area in the nasal cavities, increasing the nose’s ability to cleanse and warm inhaled air. In a flat faced animal, all of the internal nasal structures are squashed together so that the air has more trouble getting from the nostrils to the throat. So even if the nostrils are normal sized, the animals crowded nasal cavities may still block air. Although I found nothing on the subject, it is likely that when the air is not warmed before entering the throat and lungs that it also affects the animal’s body.
The next major issue for a brachycephalic breed is the soft palate. The soft palate separates the back end of the nasal cavity from the mouth cavity. Although some brachycephalic breeds have a soft palate that is short and in proportion to the shortened head, many of them have an overly long soft palate that hangs far down into the pharynx, or throat. This excessively large palate not only blocks air from moving from the nasal cavities to the trachea, but it can actually be sucked into the opening of the larynx. This may cause so much turbulence of airflow that the tissues of the palate become inflamed, thickened, and even more obstructive. One warning sign of an elongated soft palate is frequent gagging and frequent vomiting of frothy saliva. The saliva usually doesn’t have any food in it, and the animal doesn’t throw up afterward. The elongated palate seems to act like an eggbeater, so that when the dog salivates, the palate whips the saliva into a froth, the animal gags, and up it comes. Animals with an elongated soft palate are known to make throaty sounds during breathing, and if the animal has narrowed nostrils, they can snore heavily. An elongated soft palate can be fixed surgically, but it usually takes two or three surgeries to correct it.