Brachycephalic- Don’t you just want to pinch those lips?
PART 2- Nares
Anyone who has ever known a brachycephalic dog has experienced what I refer to as “sea spray” You reach in to smooch that adorable little smush face and next thing you know your face is covered with a cold wet sensation as your little friend send nasal secretions shooting all over you.
Nostrils or Nares as they are technically called are a big component of brachycephalic syndrome. Look closely at your little friends nares and you will see that they are very small compared to an average breed of dog. This is particularly an issue in the smaller brachycephalic breeds such as Boston Terriers, French and English Bulldogs.
Above are images of 2 very different sets of Nares/Nostrils. The image on the top is from the adorable pug baby from Part 1: Introduction to Brachycephalic Syndrome. The second image on the bottom is from a Labrador Retriever which is a Dolichocephalic or long nosed breed of dog. Notice how much wider and open the airway is in the Lab compared to the Pug.
Here are the same 2 images but I have highlighted the airways for you. The difference should now be clear. So what does it matter that their nostrils aren't open as wide as a Labs? Resistance to airflow from breathing through a narrow diameter opening results in many of the problems Brachycephalic breeds experience. There is a mathematical equation that defines the issue: R = 8nl / pr4. I know, I hate math to but it’s an important concept and I’m sure all of my Boulder Veterinary Hospital clientele are capable of understanding the principal. In this equation R = resistance to airflow which makes breathing hard. Think about trying to jog while only breathing through a straw. The harder you breathe the more resistance you experience and it becomes even more difficult to get the air you need to keep jogging. N= viscosity. This refers to the thickness of the air we breathe and is pretty constant. L =length and refers to the length of the airway or to maintain our analogy the length of the straw. Larger breeds would have a longer airway then smaller breeds. r = radius of the airway or straw. Radius is half the distance of the airway from the center of the circle to the edge. Pi is the constant we all know and love. This equation tells us that by doubling the radius of the airway we can reduce resistance of airflow 16 times. That’s huge! It also means that a little dog with brachycephalic syndrome whose nare/nostril is half as wide as it should be is experiencing 16 x more resistance to move air in and out of its lungs compared to a normal dog. That’s a whole heck of a lot. That increased resistance leads to swelling, inflammation and sometimes even collapse of the airway from all that pressure needed to move air down into the lungs and back out. These nares or nostrils are the narrowest part of the upper airway and therefore contribute to 60 – 80 % of the total resistance to breathing. Basically, they make a HUGE difference in how easy it is to breath. Let’s go back to our straw analogy. If you’re jogging and breathing through a little straw and then trade it for a straw with a radius that’s twice as big it sure is a whole heck of a lot easier to jog and breathe through that straw. Therefore, the size of the nostrils makes a big difference in how easy it is for a dog to breathe. This is an area where we can intervene and help these brachycephalic dogs’ live better longer lives. Ideally when breeding these dogs we would try and breed for larger airways to help minimize the problems associated with brachycephalic dogs and cats too. Stay tuned for the next chapter and we will discuss treatment for small nostrils soon.