Golden Retreiver in the woods

Respiratory Function

The Royal Kennel Club and the University of Cambridge have devised the Respiratory Function Grading Scheme  (RFGS) designed to advise owners if their dog is affected by BOAS (Brachycephalic Obstructive Airway Syndrome) and give guidance to breeders on how to lower the risk of producing affected puppies.  The program has been licensed by the Orthopedic Foundation for Animals, and RFGS screening is now available in North America.

Respiratory Function Grading Scheme Overview

Recent years have seen a significant rise in the popularity of Bulldogs, French Bulldogs and Pugs. Unfortunately all three breeds are subject to Brachycephalic Obstructive Airway Syndrome (BOAS), a condition which may cause breathing difficulties. BOAS is caused when the soft tissue in the nose and throat are excessive for the airway, partially obstructing the airway and making it difficult for them breathe normally. BOAS is a progressive disorder and can impair a dog’s ability to exercise, play, eat and even sleep. Along with conformational issues, indiscriminate breeding practices resulting from increased demand for puppies has only exacerbated the problem. Clinical signs of BOAS are variable and can include noisy breathing, exercise and heat intolerance, regurgitation and difficulty swallowing. And sadly for pet health, many owners are unaware of the disease, and often interpret breathing noises or difficulties as simply normal for the breed.

In an effort to learn more about the condition, increase awareness, and ultimately reduce the incidence of BOAS, researchers at the University of Cambridge in the UK developed the Respiratory Function Grading Scheme (RFGS). The goal of the RFGS was to develop an objective test to measure the clinical diagnosis and severity of BOAS.


The exam is conducted by a specially trained and approved veterinarian and consists of 4 steps:

  1. A short health survey regarding the dog’s breathing history.
  2. A brief physical exam while the dog is calm including auscultation where the assessor listens to the dog’s breathing with a stethoscope gently positioned on the side of the neck. This establishes a baseline for the absence of or severity of any clinic signs of BOAS.
  3. A brief exercise test consisting of a brisk three minute walk. This is designed to expose clinical signs of the disease in an otherwise calm and asymptomatic dog. It is not designed to assess cardiovascular fitness.
  4. A post exercise auscultation after increased airway activity to compare to the pre-exercise baseline.


The noises the trained veterinary assessors are listening for during auscultation include:

  • Stertor – a low pitched vibrational noise heard above the level of the larynx
  • Stridor – a higher pitched ‘sawing’ noise heard over the larynx
  • Nasal Stertor – a low pitched nasal snort/vibration
  • Nasal Stridor – a higher pitched nasal/whistle, usually heard on breathing in


The Respiratory Function Grading Scheme assigns a sliding scale of 0 to 3 to objectively diagnose BOAS:

  • Grade 0:  The dog is clinically unaffected and free of any respiratory signs of BOAS (no evidence of disease, no BOAS related noise heard even with a stethoscope)
  • Grade I:  The dog is clinically unaffected but does have mild respiratory signs linked to BOAS (noise is mild and only audible with a stethoscope)
  • Grade II:  The dog is clinically affected and has moderate respiratory signs of BOAS (noise is audible even without a stethoscope)
  • Grade III:  The dog is clinically affected and has severe respiratory signs of BOAS (noise is audible even without a stethoscope)

*** NOTE – If a dog exhibits respiratory difficulty, cyanosis or dyspnoea, it is not necessary or advisable to conduct the exercise test as these dogs are already in the Grade III range.

Both Grade 0 and Grade I are considered to be clinically BOAS unaffected as they exercise without difficulty and do not appear to have any clinical signs related to airway obstruction.

In Grades II and III, when stertor or stridor noise is heard without a stethoscope, whether intermittent or continuous, these dogs are considered clinically affected with clinical signs affecting quality of life. These dogs should be monitored and may require veterinary treatment.

Using the RFGS grades and the guidelines in the chart below, concerned responsible breeders can apply the selective genetic pressure to reduce the chances of producing puppies affected by BOAS. However, since the inheritance of BOAS is not fully understood and is not entirely predictable, this guidance cannot guarantee that all puppies from unaffected parents will be free of BOAS.

RFGS Grading Scale

RFGS Exam Registration Procedures

All owners are encouraged to use OFA Online to pre-register for RFGS exams as follows:

  • Log in to your OFA Online account, or if a new user, register for an OFA Online Account at:
  • From the owner dashboard, select CREATE NEW APPLICATION
  • Enter the dog’s information
    • If the dog has an existing OFA record, you may be able to pre-populate many of the fields by entering the registration or microchip numbers and hitting the search icon
  • After entering the dog’s info, scroll down and select Online Exams
  • Select Respiratory Function Grading Scheme OR if known, the specific clinic in the Upcoming Health Clinics list
  • Complete the brief pre-clinic breathing related health survey for this dog
  • Type your name to agree to the RFGS Terms
  • Enter your payment information. This will cover the OFA registration fees.  It does NOT cover the actual exam fee which is set by the host clinic or examining veterinarian.  The charge will NOT post until the completion of the exam when the results are imported into the OFA database.
  • This completes the pre-registration process, you will receive an email confirming registration with a .pdf attachment of the RFGS exam form

Some RFGS exam clinics may accept walk-ins.  If so, owners will need to complete the RFGS Application Form.

RFGS Application Form


OFA registration is required for all exam participants.  The OFA registration fee is $15.  The RFGS veterinary exams are priced separately, and the fee is determined individually by the examining veterinarian.

Release of Exam Results

All exam results are recorded in the OFA database and shared with the international team of researchers and collaborators at the University of Cambridge for statistical purposes.

Dogs receiving Grades 0 or I are considered clinically unaffected by BOAS, and will received OFA certification numbers.  Results for Grades 0 and I are released by default and are posted on the OFA website.  Grade II and III results are only released IF the owner authorizes release of the results.

Minimum Age, Repeat Exams, Breed Eligibility

The screening program is currently open to Pugs, Bulldogs, and French Bulldogs.  Other brachycephalic breeds can participate in the exams, however they are ineligible at this time for certification.

The minimum age for RFGS testing is 12 months.  Exams on dogs under 12 months of age are considered preliminary and are ineligible for certification.

While recertification is not required, if the dog is under 24 months of age at the time of the examination it is recommended that they have annual veterinary health checks as BOAS can develop later in life.

Exam Availability

Any approved examiner can perform the RFGS at their veterinary practice, or in their teaching hospital if in an academic setting.  Appointments should be made directly through the examiner or their staff.

Exams may also be offered in clinic setting such as health clinics sponsored by dog clubs.  The OFA must approve these events, and they can be found on the OFA’s Health Clinic Calendar at:

Inquiries from clubs interested in organizing a RFGS screening event should be addressed to the OFA at:  The following RFGS Clinic Planning Guidelines will help the organizers plan a successful clinic.

RFGS Clinic Planning Guide

General Exam Guidelines

  • The exams should be performed in a quiet, calm, and private area, free from loud noise and distractions.
  • The exams and the exercise test must be done in a climate controlled environment where the dog is not subject to additional stress from heat. The ambient temperature should be recorded as part of the exam.
  • Initial examination prior to the exercise test: the dog should be kept as calm as possible with gentle restraint.  The owner should be allowed to be present.  If the dog appears stressed, allow a reasonable period of time for the dog to calm down as this could adversely affect the exam results.  If unable to calm the dog down, proceed with the exercise test, and use the post exercise exam results to determine grading.
  • Exercise test: The test is designed to keep the dog physically active for 3 minutes at a brisk trot of approximately 4-5 miles per hour.  The dog may be led by the owner or a volunteer.  Because it is important to maintain an acceptable speed to test the airway system, it is recommended the walkers use a smart phone app which is able to monitor their speed.  Dogs should not be pulled.  Bathroom breaks should be accommodated if necessary.
  • If the dog cannot manage the appropriate pace, because of obesity, arthritis, anxiety or stubbornness, then a fast walk should be attempted, and the speed recorded in the exam notes.
  • If at any time during the exercise test the dog shows signs of distress, the test should be halted. Dogs exhibiting varying degrees of dyspnea (difficulty breathing) should automatically receive a Grade II or III depending on severity, and presence or absence of cyanosis or syncope.
  • Examination following the exercise test: The dog should be auscultated immediately following the exercise test using the same procedures and guidelines as the pre-exercise exam.
  • Functional grading: The clinical grading should be based on respiratory signs both pre and post exercise.  The highest grade from any of the three categories (respiratory noise, inspiratory effort, dyspnoea/cyanosis/syncope) should be given as the final grade.

RFGS Examiners

The following veterinarians have been approved as OFA RFGS examiners as of Spring 2024.  Email is the preferred method of contact.  RFGS appointments can be made at their hospitals or clinics, or they can be contracted to perform RFGS exams at health screening clinics.  The list will continue grow in numbers and by geography over time, but the roll out is slow as all approved examiners must shadow under an approved examiner in a clinical setting in order to gain familiarity with the exam protocol and gain experience and proficiency in the grading scheme before becoming approved.


Lynelle Johnson, DVM, DACVIM (UC Davis),


Milan Hess, DVM, DACT (Colorado Veterinary Specialty Group),


Carla Barstow, DVM, Highland Pet Hospital,

Kathleen Ham, DVM, DACVS (UFL),


Allan Frank, DVM (Hunt Valley Animal Hospital),

Tim Cujdik, DVM (Hunt Valley Animal Hospital),

Melanie Donis, DVM (Companion Care Veterinary Hospital),


Elizabeth Rozanski, DVM, DACVIM (Tufts),

MaryAnne Mack, DVM (Feeding Hills Veterinary Hospital),


Amanda Bolyard, DVM (Heritage Animal Hospital),


Cheryl Lopate, DVM, DACT (Wilsonville Veterinary Clinic),

Eleas Wu, DVM, DACT (Wilsonville Veterinary Clinic),


Blair Cornman, VMD (Animal Hospital of Signal Mountain),


Kelley Thieman, DVM, DACVS (TX A&M),


Carrie Stefaniak, DVM, (Sunrise Veterinary Services),

Canada – Ontario

Allison Collier, DVM (U of Guelph),

Ameet Singh, DVM, DACVIM (U of Guelph),

Matthew Wittenrich, DVM,

Jenn Woods, DVM,

Canada – Alberta

Natasha Borowski, DVM (Wetaskiwin Animal Clinic),

Erika Duperreault, DVM (Crestwood Veterinary Centre),

Dr. Yanhui Qi (Calgary Holistic Veterinary Clinic),

Veterinary Approval Process

In order to help ensure inter and intra examiner reliability, veterinarians must participate in a training/shadowing session under the guidance of one of our core veterinary examiners to become approved.  At this time the roll out is slow and deliberate in order to control and maintain confidence in the exam protocol and grading.  As additional training opportunities become available, the information will be shared here.

Upcoming Clinics:

No Additional Clinics Scheduled At This Time

Details are provided on the OFA Health Clinic Calendar:

Dog must be pre-registered using the OFA Online Tool.  Details are provided on this page in the Exam Registration Procedures.