Brachycephalic Airway Disease: Grading, Surgery, and What "Normal Snoring" Hides
Snoring and snorting in a flat-faced dog aren't normal. How BOAS is graded, which breeds are most at risk, and what surgery does in the long term.
Written by thecanineledger
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If your flat-faced dog is struggling to breathe, has blue or grey gums or tongue, or collapses, especially in warm weather or after exercise: go to a vet now. Keep the dog cool and calm on the way.
In UK primary-care records, Pugs had about 54 times the odds of being diagnosed with brachycephalic obstructive airway syndrome (BOAS) compared with other dogs (O’Neill et al., Canine Medicine and Genetics 2022). French Bulldogs had about 31 times the odds (O’Neill et al., Canine Medicine and Genetics 2021).
While many owners hear the snoring and snorting as part of the breed’s charm, researchers warn that this way of thinking hides real disease. This page explains what BOAS is, how it is graded, which breeds are at risk, and what surgery can and can’t do.
1. What BOAS is
Flat-faced (brachycephalic) dogs have short skulls. The soft tissues of the nose and throat don’t shrink to match, so the airway is crowded.
A 2026 Cambridge study describes the problem: “Abnormalities in the nasal cavity such as stenotic nares and aberrant turbinates result in impairment of nasal airflow” (Tomlinson et al., PLoS One 2026). Stenotic nares are narrow nostrils.
The signs. “Clinically affected dogs demonstrate noisy breathing, described in terms of stertor and stridor, and dogs are evaluated for signs of respiratory distress or exercise intolerance.” Stertor is a low snoring sound. Stridor is a higher-pitched noise.
Our note: The first two sentences of section 1 are our plain-language summary, not quoted.
2. Why “normal for the breed” is a problem
A 2015 VetCompass study found upper respiratory disorders in 22.0% of extreme flat-faced dogs, against 9.7% of comparison breeds (O’Neill et al., Canine Genetics and Epidemiology 2015).
The authors warn about “a pervading acceptance of some URT disorders especially within some brachycephalic breeds as ‘normal for breed’”. URT means upper respiratory tract. They add: “This normalisation phenomenon may blind owners and veterinarians to URT disorders in commonly affected breeds and lead to under-reporting and under-diagnosis.”
In other words, a dog that snores loudly every night, snorts at rest, or tires quickly on walks may have a treatable disease.
→ Choosing a Breed or a Mix: The Health Data Breeders Don’t Lead With
3. How BOAS is graded
Researchers at the University of Cambridge developed a grading system using a short exercise test. A vet listens to the dog’s breathing before and after.
| Grade | What it means |
|---|---|
| 0 | No breathing noise or difficulty after the test |
| 1 | Mild. Noise “only detectable with stethoscope auscultation” |
| 2 | “Respiratory noise is audible without a stethoscope” |
| 3 | “The most severe status”: unable to exercise, or signs of respiratory distress |
The study says “Grade 2 and Grade 3 BOAS grades are considered to be clinically significant.”
A health scheme. The grading “has since been implemented as a health scheme as the official Respiratory Function Grading Scheme run by the UK Kennel Club (KC) and the University of Cambridge in French Bulldogs, Bulldogs and Pugs”. The study says it “is currently used in many countries across the world”.
If you are buying a puppy. Ask whether the parents have been graded. A grade tells you more than a breeder’s description of the dog’s breathing.
Our note: “Ask whether the parents have been graded” is our advice. The grading scheme isn’t available everywhere.
4. Which breeds are at risk
The three most studied. Bulldogs, French Bulldogs and Pugs.
Fourteen more breeds. The 2026 Cambridge study graded 898 dogs from 14 other flat-faced breeds in the UK. “The Pekingese and Japanese Chin, had the highest rates of BOAS with only 10.9% and 17.4% being Grade 0 respectively.” Neither differed significantly from the three popular breeds.
Six breeds had at least half their dogs at Grade 0: the Staffordshire Bull Terrier, Cavalier King Charles Spaniel, Chihuahua, Boxer, Affenpinscher and Pomeranian.
Risk factors. Across all 14 breeds, “three factors were significantly correlated with BOAS: higher body condition score, nostril stenosis, and lower craniofacial ratio (more extreme facial hypoplasia).” In plain terms: being overweight, having narrow nostrils, and having a flatter face.
Weight is the one you can change. Keeping a flat-faced dog lean is one of the few risk factors under an owner’s control.
→ Heatstroke: It Isn’t Just Hot Cars
5. What surgery can and can’t do
The 2026 study notes that “Surgery is often the treatment of choice for many clinically affected dogs and weight loss, medication and conservative management strategies may be implemented to reduce the impact of ongoing clinical signs.”
Long-term results. A second Cambridge study followed dogs years after surgery. Only 32 of 117 dogs were available for long-term assessment. In those dogs, “Improvements in RFG and BOAS Indices seen following surgery were maintained over time.” RFG is respiratory functional grade.
Owner impressions didn’t match the measurements. “55% believed their dogs no longer had breathing problems” and “39% believed their dog still had breathing problems”. The two groups’ long-term BOAS index scores were similar (Johnson et al., Veterinary Surgery 2026).
What this means for you. Surgery can bring lasting improvement. It doesn’t give a dog a normal airway, and how a dog seems at home isn’t a reliable guide to how well it breathes.
Our note: We don’t cover surgery, its anaesthetic risks in these breeds, or the best age for it.
Our note: “It doesn’t give a dog a normal airway” is our inference. Johnson 2026 reports long-term improvement, not a return to Grade 0.
→ How Risky Is Anaesthesia for My Dog?
6. What we could not verify
| Commonly said | What we found |
|---|---|
| “Snoring is normal for the breed” | No. VetCompass researchers say this belief may blind owners and vets to disease. |
| “Only Pugs and Bulldogs get BOAS” | No. Pekingese and Japanese Chin had similar rates in a 2026 study of 14 more breeds. |
| “Surgery fixes it” | It improves it. Improvements lasted in a small long-term study, but this doesn’t mean the airway is normal. |
| “If my dog seems fine after surgery, it is fine” | Not reliably. Owners’ impressions didn’t match objective measurements. |
| “Weight doesn’t matter” | It does. A higher body condition score was linked to BOAS. |
Sources
- O’Neill DG, Sahota J, Brodbelt DC, Church DB, Packer RMA, Pegram C. Health of Pug dogs in the UK: disorder predispositions and protections. Canine Med Genet 2022: VetCompass, 4,308 Pugs and 21,835 other dogs
- O’Neill DG, Packer RMA, Francis P, Church DB, Brodbelt DC, Pegram C. French Bulldogs differ to other dogs in the UK in propensity for many common disorders: a VetCompass study. Canine Med Genet 2021: VetCompass, 2,781 French Bulldogs and 21,850 other dogs
- O’Neill DG, Jackson C, Guy JH, et al. Epidemiological associations between brachycephaly and upper respiratory tract disorders in dogs attending veterinary practices in England. Canine Genet Epidemiol 2015: VetCompass, 1,200 dogs
- Tomlinson F, Liu NC, Sargan DR, Ladlow JF. A cross-sectional study into the prevalence and conformational risk factors of BOAS across fourteen brachycephalic dog breeds. PLoS One 2026: 898 dogs. Funded by The Kennel Club Charitable Trust, which had no role in the study
- Johnson DA, Liu NC, Ladlow JF. Comparison of short- and long-term objective respiratory outcomes after surgery for brachycephalic obstructive airway syndrome. Vet Surg 2026: 32 dogs at long-term follow-up
Always confirm with your vet before acting on anything on this page.