Flat-Faced Breeds: Airway Grading, Anesthesia Risk, and What to Ask

By Morgan Reyes

Noisy Breathing Is a Graded Sign, Not a Breed Quirk

Constant snoring, snorting or noisy breathing in a pug, French bulldog or bulldog is a medical finding that a vet can grade from 0 to 3, not just "how the breed sounds." The grade comes from a short exam that includes a three-minute quick-paced walk, because a resting check can miss it. Anesthesia carries extra risk for these dogs, but the numbers say that risk is concentrated in recovery. That is a reason to plan monitoring, not a reason to avoid care your dog needs.

Heat risk in these breeds is a separate question, covered in Heat Safety for Pets: The Watch-vs-Emergency Line, so this page stays on airway grading, anesthesia, and the questions worth asking.

If you have a procedure booked, skip to the anesthesia numbers and then the question list. If you are here because of the snoring, read in order.

What BOAS Is, in Plain Terms

BOAS stands for brachycephalic obstructive airway syndrome. "Brachycephalic" means short-skulled. In an affected dog, the soft tissue in the nose and throat is too much for the space available, so it partly blocks the airway. The Royal Kennel Club and the University of Cambridge describe it as a condition that can worsen over time and can interfere with exercise, play, eating and sleeping.

Two anatomical terms are worth knowing, because they come up at the clinic. Stenotic nares are nostrils that are too narrow and can collapse inward when the dog breathes in. An elongated soft palate is a flap at the back of the mouth that is too long and reaches into the opening of the windpipe. Cambridge ties the low snoring sound (stertor) to the palate and a low nasal snort to nostril and nasal blockage.

The structure of the face is part of the risk. In a 2015 study of skull shape, BOAS only occurred in dogs whose muzzles were less than half the length of the skull, and thicker necks and obesity raised risk further (Packer and colleagues, PLoS One). The scheme's core breeds are pugs, French bulldogs and bulldogs, and the Royal Kennel Club page lists a wider set of breeds now eligible, so check that list rather than assuming your dog is or is not included.

The 0-3 Grades, What Each One Means

Grades 0 and 1 are "clinically unaffected"; grades 2 and 3 are "clinically affected." The Respiratory Function Grading Scheme was developed by the University of Cambridge and the Royal Kennel Club, and it is a screening result rather than a lifelong label.

Wording follows the Royal Kennel Club's scheme page. OFA adds that grade 1 noise is mild and heard only with a stethoscope, while grade 2 and 3 noise is audible without one.

A trained vet listens to the breathing with a stethoscope while the dog is calm, walks or trots the dog at a quick pace for three minutes, then listens again. Dogs are assessed from 12 months old and re-graded every two years, and the Royal Kennel Club says plainly that "these grades have an expiry date." If a dog is already struggling to breathe or has blue-tinged gums, the exam materials say the exercise test should not be done, because the dog is already in the grade 3 range. Ask the assessing vet how often to recheck your own dog.

The scheme is UK-centred, and North American access is still growing. OFA has licensed it for the United States and Canada. When we checked OFA's Respiratory Function page on 29 September 2026, it said RFGS screening is "now available in North America" and listed approved examiners "as of Summer 2026," with a note that the roll-out is slow because each examiner must train under an approved one. So availability depends on where you live. Ask your clinic whether a trained assessor is nearby, and if not, ask your own vet to describe the breathing findings in the grade's terms.

Why "He Breathes Fine at Rest" Does Not Settle It

A resting check catches fewer cases than a check after exertion. A Cambridge-led validation study (Riggs and colleagues, Vet Surg, 2019) tested how often a clinical exam picked up BOAS in pugs, French bulldogs and English bulldogs. Sensitivity, meaning the share of truly affected dogs the exam flagged, was 56.7% before exercise, 70% after a five-minute walk, and 93.3% after a three-minute trot. The exercise test included 44 dogs.

So about four in ten affected dogs were missed by a resting exam alone, in that sample. Cambridge puts it in words: signs "may not be present at rest in some moderately affected dogs." That is why the grade includes exertion.

Two limits apply. The study covered three breeds, so it says less about other flat-faced dogs. And the record notes that The Kennel Club Charitable Trust supported the Cambridge BOAS group, the research group behind the scheme, so weigh it as such.

What to do with this: describe what you see after play or a brisk walk, not just on the couch. The noise after exertion is the finding your vet most needs to hear about.

Signs Worth Writing Down Before the Appointment

Keep a short note for a week or two. These items come from the Cambridge description of BOAS.

• Noise type. Low snoring or snorting versus a high-pitched, wheezy sound. Cambridge calls the high-pitched sound stridor and says it usually points to a narrowed or collapsed voice box.
• When it happens. At rest, when excited, when eating, or after exercise.
• Breathing effort. Open-mouth breathing, or visible work to draw a breath.
• Sleep. Loud breathing that stops and starts, or pauses in breathing. Cambridge describes periods of no breathing during sleep in these dogs and calls the condition life-threatening. Some owners also report dogs sleeping sitting up. That is an owner observation, not a cited sign, but mention it.
• Eating and regurgitation. Cambridge notes regurgitation is common in BOAS-affected dogs.

Cambridge says that when the blood is inadequately oxygenated, a bluish color shows on the tongue and gums, and that a dog whose oxygen level is not stabilized quickly "may collapse or become unconscious." Treat that as an emergency.

Anesthesia Risk, Read Correctly

Overall complication rates were similar; the extra risk was concentrated after anesthesia. That is the correct reading of the best-known paper, and it is not what most summaries say.

The paper is Gruenheid and colleagues in the Journal of the American Veterinary Medical Association (2018). It is a retrospective study at one Ohio teaching hospital, covering general anesthesia for routine surgery or advanced imaging in 2012. It compared 223 flat-faced dogs with 223 matched dogs of other breeds, healthy to moderately ill (ASA I to III), with emergency cases excluded.

Overall, about half of both groups had some complication, so in the raw counts being flat-faced did not make a problem more likely overall. After controlling for other factors, being flat-faced was linked to somewhat higher odds of a problem during anesthesia (1.57) and much higher odds of one afterward (4.33). Both deaths were flat-faced dogs. The authors' explanation is that airway obstruction can occur after extubation, which is the moment the breathing tube comes out, and they advise careful monitoring.

The limits of this study:

• It is one hospital and one calendar year, 2012.
• The 4.33 estimate rests on only 39 post-anesthetic events in total, which is why its confidence interval is so wide (1.85 to 10.15). Treat it as one hospital's estimate, not a fixed multiplier.
• Emergency cases and sicker dogs (ASA IV and V) were excluded.
• Body condition score was not available, so weight could not be separated out.
• Two deaths cannot support a death rate.

This argues for planned monitoring through recovery, not for declining needed anesthesia. The condition that makes anesthesia riskier is also one that gets worse untreated. For other pre-procedure questions a vet may raise, see the senior pet wellness visit checklist, and for a related decision about anesthesia and dental care, see why anesthesia-free dental cleaning falls short.

What Is and Is Not in Your Control

Body condition is the one modifiable risk factor the evidence names. Packer and colleagues (2015) found obesity increased the risk of BOAS. A 2017 study of 604 pugs, French bulldogs and bulldogs (Liu and colleagues, PLoS One) found stenotic nostrils were associated with BOAS in all three breeds, and that a higher body condition score raised risk in pugs and bulldogs. Both are observational, so they show association, not proof that weight loss reverses the condition. If you are unsure where your dog sits, the body condition check walks through it.

Muzzle length and nostril shape are structural. They are set by breeding, which makes them a question for a breeder or a future puppy buyer rather than something an owner can change. Whether an airway operation is warranted is your vet's call after the breathing has been graded, so this page does not cover it.

Air Travel: What to Check

Airline and carrier rules for snub-nosed dogs change and vary by carrier, so this page prints none of them. Our cabin-vs-cargo flying guide covers the carrier and airline rules and the container-size rule IATA sets for snub-nosed breeds. Before you book, ask your vet whether your dog's grade and history make travel sensible at all.

Questions to Ask the Clinic

Tell the clinic your dog is flat-faced when you book, not on the day. Then ask:

1. Do you see flat-faced dogs often?
2. Can you grade my dog's breathing, including after a brisk walk or trot?
3. Is a trained assessor available near me?
4. What will you note on my dog's file for the procedure team?
5. Who watches my dog until fully awake?
6. What do you look for after the breathing tube is out?
7. Will my dog stay under observation before going home?
8. What do you want to know about my dog's snoring and sleep?
9. Which signs after going home mean I should call right away?

Bring the notes from the signs list too. Then book a breathing check with your own vet, take these questions along, and check body condition with the weight guide beforehand.

Bottom line: noisy breathing in a flat-faced dog is worth grading, not accepting. A trained vet grades it 0 to 3 after a three-minute trot, because a resting check can miss it (56.7% sensitivity at rest versus 93.3% after the trot, in 44 dogs). In the main anesthesia study, overall complication rates were similar (49.8% vs 48.4%), the excess was after anesthesia (13.9% vs 3.6%, adjusted OR 4.33, 95% CI 1.85 to 10.15, from 39 events at one hospital), and the sensible response is a plan for recovery monitoring.

FAQ

What is a BOAS grade?

A 0 to 3 score from the Respiratory Function Grading Scheme, developed by the University of Cambridge and the Royal Kennel Club. Grades 0 and 1 are clinically unaffected; grades 2 and 3 are clinically affected.

Is snoring normal in a pug or French bulldog?

Common, yes; normal, not necessarily. Cambridge notes signs may be absent at rest in moderately affected dogs, so ask for a grade rather than a shrug.

Are flat-faced dogs really higher risk under anesthesia?

In one Ohio hospital's 2012 data, overall complications were similar (49.8% vs 48.4%), but complications afterward were more common (13.9% vs 3.6%), and both deaths were flat-faced dogs. One hospital and 39 events mean the exact multiplier is uncertain.

Why does the vet make my dog trot?

Because noise can be missing at rest. A clinical exam picked up BOAS 56.7% of the time before exercise and 93.3% after a three-minute trot, in a 44-dog study.

What should I ask my vet before my flat-faced dog has anesthesia?

Tell the clinic your dog is flat-faced, then ask who monitors breathing through recovery, what they watch for once the breathing tube is out, and whether your dog stays under observation before going home.

Keep reading

• Body Condition Check: Is Your Pet at a Healthy Weight?. Weight is the modifiable factor named in the conformation studies.
• Senior Pet Wellness Visit Checklist. Other questions worth raising before any procedure.
• Flying With a Pet: Cabin vs. Cargo. Carrier and airline rules, kept current in one place.

A Note on Scope

This article is for informational purposes only and isn't a substitute for advice from a veterinarian about an individual animal. A dog with blue-tinged gums or tongue, struggling to breathe, or collapsing needs an emergency clinic immediately, not home monitoring.

Sources

• Royal Kennel Club, Respiratory Function Grading Scheme. Fetched 29 September 2026. Source for the grade definitions, the three-minute quick-pace exam, assessment from 12 months, the two-year repeat, and "these grades have an expiry date."
• University of Cambridge Department of Veterinary Medicine, BOAS: recognition and diagnosis. Fetched 29 September 2026. Source for noise types, cyanosis and collapse, sleep-disordered breathing, regurgitation, and signs that may be absent at rest.
• OFA, Respiratory Function (RFGS). Fetched 29 September 2026. Source for North American licensing and availability, the examiner list "as of Summer 2026," and the exam steps.
• Gruenheid MC et al., "Risk of anesthesia-related complications in brachycephalic dogs," JAVMA 2018;253(3):301-306 (DOI 10.2460/javma.253.3.301). Abstract and full text read 29 September 2026. Source for every anesthesia figure and limit on this page.
• Riggs J et al., "Validation of exercise testing and laryngeal auscultation for grading BOAS in pugs, French bulldogs, and English bulldogs," Vet Surg 2019;48(4):488-496. Abstract read 29 September 2026; full text not read. Source for the sensitivity figures.
• Packer RMA et al., "Impact of Facial Conformation on Canine Health: Brachycephalic Obstructive Airway Syndrome," PLoS One 2015;10(10):e0137496. Abstract read 29 September 2026. Source for muzzle length, neck girth and obesity.
• Liu NC et al., "Conformational risk factors of brachycephalic obstructive airway syndrome (BOAS) in pugs, French bulldogs, and bulldogs," PLoS One 2017;12(8):e0181928. Abstract read 29 September 2026. Source for nostril stenosis and body condition score findings.