A Bulldog's face is instantly recognizable, but appearance is only the starting point for understanding breathing. Research on brachycephalic obstructive airway syndrome (BOAS), heat-related illness, and breeding assessments asks different questions. Knowing what each study measured helps you read a parent's screening record, put a risk figure in context, and ask more useful questions before choosing a dog.

Why the Airway Shapes Everyday Life

Brachycephalic means flat-faced. In a 2026 PLOS ONE paper, researchers described BOAS as a common problem in Bulldogs, French Bulldogs, and Pugs, linked to their distinctive skull structure. Their work examined respiratory function and nostril stenosis, meaning narrowing of the nostrils. These are related aspects of the airway, but they are recorded as distinct traits.

For a prospective owner, the useful distinction is between how a dog looks and what an assessment records about breathing. A description such as "typical Bulldog" does not tell you a respiratory grade. Ask for the assessment details rather than trying to interpret appearance as a test result. The research concerns measured function as well as physical features.

Heat: What a UK Emergency-Care Study Found

A 2024 Veterinary Record study used VetCompass records from 167,751 dogs under UK emergency veterinary care in 2022. Researchers identified 384 heat-related illness events and reported an event fatality rate of 26.56%. They described 2022 as the UK's hottest year to date at the time of the study.

Flat-faced dogs had 4.21 times the odds of heat-related illness compared with dogs with medium-length skulls. This comparison was between skull-shape groups, rather than a Bulldog-only estimate. The fatality figure concerned illness events in an emergency-care setting; it did not describe all dogs exposed to warm weather. The authors also noted missing clinical information, especially bodyweight. Keep that setting attached to the figures when discussing them.

How the UK Respiratory Function Grading Scheme Works

The Royal Kennel Club and the University of Cambridge introduced the Respiratory Function Grading Scheme in 2019. The 2026 PLOS ONE analysis of the scheme describes a standardized exercise assessment for dogs considered for breeding. Functional grades range from 0 to 3. Grades 0–1 are considered clinically unaffected; grades 2–3 indicate BOAS of increasing severity.

The researchers analyzed data from more than 4,000 dogs alongside pedigree records. They estimated heritability at 0.21–0.49 for respiratory grade and 0.31–0.39 for nostril stenosis. Heritability is a population-level genetic estimate, rather than a puppy's chance of receiving a particular grade. When reading a parent's record, ask for the grade itself and the scheme name. "Tested" alone does not explain the result.

What Finland's Breeding Test Showed

A 2024 study of Finnish BOAS testing during 2017–2022 examined 957 participating dogs. The test combined exercise and recovery assessment, veterinary grading of upper respiratory signs before and after exercise, and an assessment of nostril narrowing. English Bulldogs, French Bulldogs, and Pugs made up 80% of the dogs.

English Bulldogs had the highest proportion failing the exercise component, at 11%. Among English Bulldogs, 28% had moderate-to-severe BOAS signs and 40% had moderate-to-severe nostril narrowing. The authors concluded that exercise testing alone did not sufficiently identify dogs with moderate-to-severe signs. They called for exercise tolerance, respiratory signs, and nostril assessment to be considered together. Those findings explain why a pass-or-fail answer about exercise leaves out part of the picture.

What People Say They Prefer

A 2025 Veterinary Record survey asked 4,899 UK participants to rate images of English Bulldogs, French Bulldogs, and Pugs with typical, less extreme, and more extreme body shapes. Less extreme versions received significantly higher ratings for attractiveness, perceived health, and the ethics of breeding. Owners of purebred flat-faced dogs also rated the less extreme versions more highly.

This was a study of people's responses to images. Perceived health is what participants thought about an image, rather than a veterinary finding. The authors noted that participants were UK-based and largely female, which limits how broadly the results can be applied.

Questions Worth Asking a Breeder

Ask whether each parent has a respiratory assessment, which scheme was used, and what the recorded grade means. Ask whether the paperwork includes nostril findings as well as exercise performance. If a result is described only as a pass, ask what that word covers. Our guide to questions for a Bulldog breeder provides the wider context for discussing parental records. Keep the actual findings at the center of the conversation rather than relying on a reassuring label.

When comparing records, write down which findings are present and which questions remain unanswered. This keeps a general description of a parent from standing in for the specific information you were looking for.