Title: Brachycephalic obstructive airway syndrome

{{Short description|Condition affecting short-nosed dogs and cats}}
[[File:Bulldog portrait Frank.jpg|thumb|The [[English bulldog]], a typically [[brachycephalic]] [[dog breed]], may have brachycephalic syndrome.]]
[[File:Exotic sh 12months.jpg|thumb|A peke-face [[Exotic Shorthair]].]]

'''Brachycephalic obstructive airway syndrome''' (BOAS), also known as '''brachycephalic airway obstructive syndrome''' (BAOS), '''brachycephalic airway syndrome''' (BAS), and '''brachycephalic syndrome''' (BS),&lt;ref name=upenn&gt;{{Cite web|url=http://www.vet.upenn.edu/docs/default-source/ryan/ryan-report-bas-article-2.pdf|title=Brachycephalic Airway Syndrome (BAS)|date=October 4, 2017 |publisher=[[University of Pennsylvania School of Veterinary Medicine]]}}&lt;/ref&gt; is a [[pathological]] condition affecting [[brachycephalic|short nosed]] [[dog]]s and [[cat]]s which can lead to severe [[respiratory distress]]. There are four different anatomical abnormalities that contribute to the disease, all of which occur more commonly in brachycephalic breeds: an elongated [[soft palate]], [[stenotic nares]], a hypoplastic [[trachea]], and everted [[laryngeal saccules]] (a condition which occurs secondary to the other abnormalities). Because all of these components make it more difficult to breathe in situations of exercise, stress, or heat, an animal with these abnormalities may be unable to take deep or fast enough breaths to blow off [[carbon dioxide]]. This leads to distress and further increases respiratory rate and heart rate, creating a vicious cycle that can quickly lead to a life-threatening situation.

Brachycephalic dogs have a higher risk of dying during air travel and many [[commercial airline]]s refuse to transport them.&lt;ref&gt;{{Cite web|url=https://www.nytimes.com/2019/04/24/travel/dogs-cats-pets-flying-international.html |title=Taking Your Dog on a Plane Just Got Harder|first=Lisa|last=Gay|date=April 24, 2019|website=[[The New York Times]]|url-access=subscription|archive-url=https://web.archive.org/web/20190424133023/https://www.nytimes.com/2019/04/24/travel/dogs-cats-pets-flying-international.html |archive-date=April 24, 2019}}&lt;/ref&gt;&lt;ref&gt;{{Cite web|url=https://www.avma.org/resources-tools/pet-owners/petcare/air-travel-and-short-nosed-dogs-faq|title=Air travel and short-nosed dogs FAQ|publisher=[[American Veterinary Medical Association]]}}&lt;/ref&gt;

Dogs experiencing a crisis situation due to brachycephalic syndrome typically benefit from oxygen, cool temperatures, [[sedatives]], and in some cases more advanced medical intervention, including [[intubation]].

== Causes and risk factors ==
[[File:Brachycephalic Dog Airway.svg|thumbnail|This diagram illustrates what the airway structure looks like in a brachycephalic dog; in this case, a Boxer.&lt;hr /&gt;&lt;span style=&quot;background:#e0e0f0&quot;&gt;&lt;small&gt;1.&amp;nbsp;Nasal&amp;nbsp;cavity 2.&amp;nbsp;Oral&amp;nbsp;cavity 3.&amp;nbsp;Soft&amp;nbsp;palate 4.&amp;nbsp;Pharynx 5.&amp;nbsp;Larynx 6.&amp;nbsp;Trachea 7.&amp;nbsp;Esophagus 8.&amp;nbsp;Nasopharynx 9.&amp;nbsp;Hard&amp;nbsp;palate&lt;/small&gt;&lt;/span&gt;&lt;hr /&gt;The brachycephalic dog has a shorter snout which causes the airway to be shorter, that means all the parts that make up the airway get compressed. Due to this phenomenon, a brachycephalic dog has an elongated soft palate which can cause most of the problems with the dog's breathing. They can also have problems getting enough air in because of their elongated soft palate and shorter airway.]]

The primary anatomic components of BOAS are [[stenotic nares]] (pinched or narrowed nostrils) and [[soft palate]] [[hyperplasia]].&lt;ref name=upenn /&gt; Other anatomical factors that are involved include aberrant [[cochae]], skull confirmation, [[macroglossia]], [[glottic stenosis]], and tracheal [[hypoplasia]]. These anatomical factors can also result in secondary conditions like [[everted laryngeal saccules]], partial collapse of the [[dorsonasal pharynx]], and [[laryngeal collapse]].&lt;ref name=&quot;sasts&quot;/&gt;

Other risk factors for BOAS include a lower craniofacial ratio (shorter muzzle in comparison to the overall head length), a higher neck girth, a higher body condition score, and neuter status.&lt;ref name=&quot;UFAWconference&quot;&gt;{{cite conference |title=Short Muzzle; Short Of Breath? An Investigation Of The Effect Of Conformation On The Risk Of Brachycephalic Obstructive Airway Syndrome (BOAS) In Domestic Dogs |date=2013|conference=UFAW Symposium, Barcelona|url=https://www.ufaw.org.uk/downloads/events/ufaw-2013-symposium-abstract-booklet-final-v3.pdf|access-date=21 January 2018|website=[[Universities Federation for Animal Welfare]]|first1=RMA|last1=Packer|first2=MS|last2=Tivers|first3=A|last3=Hendricks|first4=CC|last4=Burn}}&lt;/ref&gt;

In addition to this mucosal hyperplasia and collapse of the airway can aggravate the condition.&lt;ref name=&quot;sasts&quot;&gt;{{cite book|first1=Dorothee|last1=Krainer|first2=Gilles|last2=Dupré|chapter=Brachycephalic Airway Syndrome|pages=438–458|title=Small Animal Soft Tissue Surgery | publisher=Wiley | date=2023-05-12 | isbn=978-1-119-69368-0 | doi=10.1002/9781119693741}}&lt;/ref&gt;
==Breed prevalence==
The breeds most commonly affected are the [[Bulldog]], [[French Bulldog]], [[Pug]], and [[Boston Terrier]]. Other brachycephalic breeds include: the [[Pekingese]], [[Shih Tzu]], [[Lhasa Apso]], [[Cavalier King Charles Spaniel]], [[Boxer dog|Boxer]], [[Dogue de Bordeaux]], [[Brussels Griffon]], and [[Bullmastiff]].&lt;ref name=&quot;sasts&quot;/&gt;

== Signs and symptoms ==
[[Image:Murlough Beach (05), February 2010.JPG|thumb|Breeds with less extreme brachycephalia, such as the [[Boxer (dog)|Boxer]], have less compromised thermoregulation and thus are more tolerant of vigorous exercise and heat.]]
Symptoms of brachycephaly include: snoring, [[dyspnoea]], [[emesis]], [[stridor]], [[insomnia]], [[cyanosis]], [[syncope (medicine)|syncope]], and [[dysphagia]].&lt;ref name=&quot;sasts&quot;/&gt;

Despite observing clinical signs of airway obstructions, some owners of brachycephalic breeds may perceive them as normal for the breed, and may not seek veterinary intervention until a particularly severe attack happens.&lt;ref&gt;{{cite web|title=Worrying numbers of &quot;short-nosed&quot; dog owners do not believe their pets to have breathing problems, despite observing severe clinical signs|url=http://www.rvc.ac.uk/News/PressReleases/pr1205_BreathingProblemsInDogs.cfm|publisher=The Royal Veterinary College|access-date=29 June 2013|date=10 May 2012}}&lt;/ref&gt;&lt;ref&gt;{{Cite journal | vauthors = Packer RM, Hendricks A, Burn CC | title = Do dog owners perceive the clinical signs related to conformational inherited disorders as 'normal' for the breed? A potential constraint to improving canine welfare | doi = 10.7120/096272812X13345905673809 | journal = Animal Welfare | volume = 21 | pages = 81–93 | year = 2012 | url = http://researchonline.rvc.ac.uk/id/eprint/6179/ }}&lt;/ref&gt;

After waking from surgery, most dogs that are [[Tracheal intubation|intubated]] will try to claw out their [[tracheal tube]]. In contrast, brachycephalic dogs often seem quite happy to leave it in place as it opens the airway, making it easier to breathe.&lt;ref&gt;{{cite web|last=Johnson|first=Tony | name-list-style = vanc |title=Breathless: Bulldogs, pugs need protection from the heat|url=http://www.veterinarypartner.com/Content.plx?P=A&amp;A=3262&amp;S=0&amp;SourceID=28|publisher=Veterinary Information Network|access-date=17 November 2013}}&lt;/ref&gt;

===Secondary conditions===
Other conditions may be observed concurrently. These include swollen/everted [[laryngeal saccules]], which further reduce the airway, collapsed larynx, and [[chronic obstructive pulmonary disease]] caused by the increased lung workload.

== Treatment ==
{{multiple image
| align = right
| image1 = Stenotic nares before1.jpg
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| image2 = Stenotic nares after.jpg
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| footer = Stenotic nares in a Boxer before (left) and after (right) surgery.
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Treatment consists of surgery for widening the nostrils, removing the excess tissue of an elongated soft palate, or removing everted laryngeal saccules. Early treatment prevents secondary conditions from developing.

Potential complications include hemorrhages, pain, and inflammation during and after surgery. Some [[Veterinary physician|veterinarians]] are hesitant to perform soft palate correction surgery. With CO&lt;sub&gt;2&lt;/sub&gt; surgical lasers, these complications are greatly diminished.&lt;ref&gt;{{Cite news|url=https://www.aesculight.com/case-studies/elongated-soft-palate-resection-co2-surgical-laser/|title=Elongated soft palate resection with a CO2 surgical laser|last=Arza|first=Ray | name-list-style = vanc |date=2016-09-29|newspaper=Aesculight|access-date=2017-02-06|language=en-US}}&lt;/ref&gt;

== Prevention ==
Avoiding stress, high temperatures, and overfeeding can reduce the risk. Using harnesses instead of collars can avoid pressure on the [[trachea]].

The risk of brachycephalic syndrome increases as the muzzle becomes shorter.&lt;ref name=&quot;UFAWconference&quot;/&gt; To avoid producing affected dogs, breeders may choose to breed for more moderate features rather than for extremely short or flat faces. Dogs with breathing difficulties, or at least those serious enough to require surgery, should not be used for breeding.&lt;ref&gt;{{cite web|title=Brachycephalic syndrome|url=http://www.upei.ca/~cidd/Diseases/respiratory%20disorders/brachycephalic%20syndrome.htm|publisher=Canine Inherited Disorders Database|access-date=5 November 2013|url-status=dead|archive-url=https://web.archive.org/web/20130907080637/http://www.upei.ca/~cidd/Diseases/respiratory%20disorders/brachycephalic%20syndrome.htm|archive-date=7 September 2013}}&lt;/ref&gt; Removing all affected animals from the breeding pool may cause some breeds to be unsustainable and outcrossing to non-brachycephalic breeds might be necessary.&lt;ref name=ufaw/&gt;

Although [[outcrossing]] can attempt to lengthen the average snout length within a breed over time and reduce BOAS, it is not popular with established [[Breed registry|breed registries]] who record pedigrees of purebred dogs. In 2014, the [[Netherlands|Dutch]] government passed the Animals Act and the Animal Keepers Act, and subsequent enforcement caused the [[Dutch Kennel Club]] (Raad van Beheer) in 2020 to announce they were restricting registrations within 12 dog breeds based on snout length, and encouraging outcrosses to other breeds, while promising that future generations may be eligible for registration as purebreds. This caused concern with the [[Fédération Cynologique Internationale]] (FCI), of which RvB is a member, and with the [[American Kennel Club]], both of which expressed concerns about governments legislating such matters.&lt;ref&gt;{{Cite web|url=http://www.fci.be/en/Open-letter-from-the-FCI-President-about-the-matter-of-the-registration-of-brachycephalic-breeds-in-the-Netherlands-3550.html|title=Open letter from the FCI President about the matter of the registration of brachycephalic breeds in the Netherlands|first=Dr. Tamás|last=Jakkel|date=May 20, 2020|website=[[Fédération Cynologique Internationale]]|access-date=August 27, 2021}}&lt;/ref&gt;&lt;ref&gt;{{Cite web|url=https://cqrcengage.com/akc/file/xlg4ePac6t1/statement-rvb-short-muzzled-breeds-eng-25052020.pdf|title=The current position of the short-muzzled dog breeds in the Netherlands and what preceded it|website=[[Dutch Kennel Club|Dutch Kennel Club Raad van Beheer]]|date=25 May 2020|access-date=August 27, 2021}}&lt;/ref&gt;&lt;ref&gt;{{Cite web|url=https://akcgr.org/akc/app/document/35461331|title=AKC Statement on Dutch Kennel Club 'Brachycephalic Decision: Context and a Cautionary Tale|date=June 5, 2020|author=AKC Government Relations Department|website=[[American Kennel Club]]|access-date=August 27, 2021}}&lt;/ref&gt;

==Other health problems==
[[File:Exophthalmos in pug.JPG|thumbnail|right|Exophthalmos in a pug]]
Non-airway problems associated with brachycephalia may include:
*Inflammation in skin folds
*Mating and birthing problems
*[[Malocclusion]] – misalignment of the teeth.
*Dental crowding
*Brachycephalic ocular syndrome&lt;ref name=ufaw&gt;{{cite web|title=Shih Tzu: Brachycephalic Ocular Syndrome|url=https://www.ufaw.org.uk/dogs/shih-tzu-brachycephalic-ocular-syndrome|publisher=Universities Federation for Animal Welfare|date=2011|access-date=2017-11-25}}&lt;/ref&gt; 
**[[Ectropion]]/[[entropion]] – inward/outward rolling of eyelid
**Macropalpebral fissure
**[[Lagophthalmos|Lagophthalmia]] – inability to close eyelids fully
**[[Exophthalmos]]/[[eye proptosis]] – abnormal protrusion of the eye
**Nasal fold trichiasis – fur around the nose fold rubs against the eye.
**[[Distichiasis]] – abnormally placed eyelashes rub against the eye.
**Poor tear production
**Gastrointestinal problems&lt;ref&gt;{{cite journal | vauthors = Poncet CM, Dupre GP, Freiche VG, Estrada MM, Poubanne YA, Bouvy BM | title = Prevalence of gastrointestinal tract lesions in 73 brachycephalic dogs with upper respiratory syndrome | journal = The Journal of Small Animal Practice | volume = 46 | issue = 6 | pages = 273–279 | date = June 2005 | pmid = 15971897 | doi = 10.1111/j.1748-5827.2005.tb00320.x }}&lt;/ref&gt;

==See also==
* [[Cephalic index]] – for lists of affected dog, cat, and other animal breeds

== References ==
{{Reflist}}

[[Category:Syndromes in dogs]]
[[Category:Syndromes in cats]]
[[Category:Breathing abnormalities]]