Dogs with flat faces, known as brachycephalic breeds, are the ones most likely to have breathing problems. Pugs, French Bulldogs, English Bulldogs, Pekingese, Shih Tzus, Boston Terriers, Boxers, and Cavalier King Charles Spaniels all share a shortened skull that compresses their airways into a smaller space than nature intended. The condition that results, called brachycephalic obstructive airway syndrome (BOAS), affects a striking number of these dogs: roughly 65% of Pugs, 59% of French Bulldogs, and 51% of English Bulldogs are clinically affected.
Why Flat-Faced Dogs Struggle to Breathe
Breeding for a shorter snout doesn’t shrink everything proportionally. The soft tissues inside the airway, including the tongue, the soft palate, and the tissue lining the nostrils, remain roughly the same size even though the skull is much shorter. That means too much tissue is packed into too little space, and the result is a series of physical obstructions that make every breath harder than it should be.
Three specific problems drive most of the difficulty. First, the nostrils are often pinched nearly shut, sometimes narrowed to a vertical slit that forces the dog to breathe through its mouth almost constantly. Second, the soft palate (the fleshy tissue at the back of the roof of the mouth) extends too far back and hangs over the airway opening, fluttering with each breath and partially blocking airflow. Over time, the effort of breathing against this obstruction causes the tissue to thicken further, making the problem progressively worse. Third, the tongue is disproportionately large for the shortened jaw, which pushes the soft palate even further into the airway.
Some of these dogs also have an abnormally narrow windpipe, where the cartilage rings that hold it open touch or overlap instead of forming a clean circle. While this isn’t considered the primary driver of breathing difficulty, it compounds the other problems.
Breeds Most Commonly Affected
The breeds at highest risk are those with the most extreme skull shortening. Pugs, French Bulldogs, and English Bulldogs top the list, with more than half of each breed showing clinical signs. These three have been studied most extensively, but they’re far from the only ones affected.
Pekingese, Brussels Griffons, Shih Tzus, and Continental Bulldogs also carry enough skull compression to warrant mandatory breathing tests in countries like Finland before they can be bred. Boston Terriers, Boxers, Cavalier King Charles Spaniels, Lhasa Apsos, and Affenpinschers round out the commonly cited breeds. Even mixed-breed dogs with significant flat-faced ancestry can develop the same airway issues.
Signs Your Dog Has Breathing Problems
The most obvious sign is noise. Loud snoring, snorting, and raspy breathing sounds are so common in flat-faced breeds that many owners assume it’s normal. It isn’t. Any breathing you can hear consistently without a stethoscope indicates at least a moderate level of airway obstruction.
Beyond noise, watch for excessive panting that seems out of proportion to activity or temperature, reluctance to exercise or walk, and slow recovery after even mild exertion. In more severe cases, dogs may develop blue-tinged gums (a sign they’re not getting enough oxygen), collapse during activity, or experience heat exhaustion on days that wouldn’t bother other dogs. Any history of fainting or blue gums places a dog in the most severe category of breathing impairment.
Veterinarians grade the severity on a 0 to 3 scale. A Grade 0 dog breathes quietly with no visible effort. A Grade 1 dog makes mild noise after exercise but is otherwise fine. Grade 2 dogs have moderate to severe noise and visible breathing effort after activity, with mild signs of distress. Grade 3 dogs struggle even at rest, with loud breathing, extensive chest and abdominal movement with each breath, and potential fainting episodes.
How Breathing Problems Shorten a Dog’s Life
A large Swiss study of over 137,000 dogs found that brachycephalic breeds live an average of 9.8 years, compared to 11.9 years for dogs with medium-length snouts and 11.5 years for long-snouted breeds. That’s roughly a two-year gap. Flat-faced dogs also showed increased mortality at younger ages, meaning they weren’t just dying slightly earlier on average; a disproportionate number were dying well before old age.
The shortened lifespan isn’t solely from breathing difficulty. BOAS creates a cascade of secondary problems. Chronic airway obstruction stresses the heart, disrupts sleep (yes, dogs get sleep apnea too), and makes temperature regulation unreliable, since dogs cool themselves primarily by panting. A dog that can’t pant efficiently is at constant risk of overheating.
Heat and Exercise Risks
Dogs don’t sweat the way humans do. They depend on moving air rapidly across the moist surfaces of their mouth and tongue to shed heat. A dog with a compressed airway moves less air with every breath, which means its built-in cooling system is compromised from the start. Add warm weather, humidity, excitement, or physical activity, and body temperature can spike dangerously fast.
This is why flat-faced breeds are consistently overrepresented in heat-related illness cases at veterinary clinics. Ambient temperature and humidity matter, but so do individual factors like fitness level, hydration, and the specific severity of the dog’s airway obstruction. A Pug with Grade 2 BOAS on a 28°C (82°F) day faces a very different risk than a Labrador in the same conditions.
Practical steps include exercising your dog during cooler parts of the day, keeping walks short and slow, ensuring constant access to water, and never leaving a flat-faced dog in a parked car, even briefly.
Surgical Treatment Options
Surgery can meaningfully improve breathing in affected dogs, and the best outcomes come from operating earlier rather than waiting for the condition to worsen. The two most common procedures address the two biggest obstructions: widening the nostrils and trimming the excess soft palate tissue so it no longer drapes over the airway.
These surgeries are typically done together under a single anesthetic session. Recovery generally involves a few days of soft food, reduced activity, and monitoring for swelling in the airway (the most significant short-term risk). Most dogs show noticeable improvement in breathing noise and exercise tolerance within a few weeks. Modified and newer versions of these techniques continue to be refined, but the core approach has a strong track record.
Surgery doesn’t give a flat-faced dog the airway of a Labrador. It reduces obstruction and improves quality of life, but the fundamental anatomy remains compressed. Dogs that have had corrective surgery still need careful management around heat and strenuous exercise.
What Breeding Programs Are Doing
Several countries now require breathing tests before flat-faced dogs can be bred. In Finland, English Bulldogs, French Bulldogs, Pugs, Pekingese, Shih Tzus, and Griffons must pass mandatory BOAS screening before their litters can be registered. The test requires a dog to briskly walk or trot 1,000 meters within a breed-specific time limit and fully recover (heart rate, temperature, and general condition returning to baseline) within 15 minutes. If a dog’s temperature rises above 39.5°C after the walk, it fails.
The UK Kennel Club has used a respiratory grading scheme since 2019 and advises against breeding dogs with severe BOAS signs. Sweden and Norway go further, prohibiting breeding of dogs with either moderate or severe signs. Germany has required Pugs to pass an exercise test before breeding since 2009. The Netherlands has taken the most aggressive stance: breeding of extremely flat-faced dogs has largely ceased due to a legal requirement that the muzzle must be at least 30% of the skull length.
Data from Finland’s program suggests that excluding dogs with moderate and severe BOAS signs, along with those failing the exercise test, would meaningfully reduce BOAS prevalence without dangerously narrowing the genetic pool. The challenge is that these programs are still voluntary in many countries, and demand for flat-faced puppies continues to drive breeding of dogs with extreme features.
Choosing and Living With a Flat-Faced Dog
If you’re considering a brachycephalic breed, look for breeders who perform BOAS screening and can share the results for both parents. Dogs with wider nostrils, slightly longer muzzles, and parents that passed exercise tolerance tests are more likely to breathe comfortably. Avoid breeders who dismiss noisy breathing as “just how the breed sounds.”
If you already have a flat-faced dog, pay attention to how they breathe at rest and after mild activity. Noisy breathing that you can hear from across the room, reluctance to walk more than a block, or rapid exhaustion in warm weather all warrant a veterinary evaluation. Keeping your dog at a lean weight makes a real difference, since extra fat around the neck and chest further compresses an already tight airway. Even a modest amount of weight loss can visibly improve breathing in overweight brachycephalic dogs.