Regular ArticlesBrachycephalic Airway Syndrome
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Definitions of Brachycephalic Dogs
Brachycephalic breeds have early ankylosis in the basicranial epiphyseal cartilage of the skull, which leads to chondrodysplasia of the longitudinal axis of the skull. This trait has been propagated by breeders.1, 2, 3, 4 Skull measurements define dogs as brachycephalic, dolichocephalic, and mesocephalic, and there is currently no consensus on which measurements are standard. The craniofacial angle between the base of the skull and the facial skull is 9°-14° in brachycephalic dogs, 25°-26° in
Anatomy
Stenotic nares are the result of congenital malformations of the nasal cartilages which cause medial collapse of the alae.9 The medial collapse of the alae creates a smaller opening at the nostril and increases airway resistance. The nasal cavities include 4 main passageways or meatuses, the common, dorsal, middle, and ventral nasal meatus, which are created by the dorsal and ventral nasal choanae and the hard palate.6 The nasal cavities are shortened in brachycephalic breeds and may contain
Pathophysiology
Airflow through the nasal cavities accounts for 76.5% of the total airflow resistance in the respiratory tract, and does not differ between inspiration and expiration in normal dogs.2 Brachycephalic dogs must overcome the increase in airway resistance, and therefore exhalation is forced rather than passive as observed in nonbrachycephalic breeds. Owing to the anatomic differences, brachycephalic dogs have an increased resistance to airflow and an increased intraluminal pressure gradient during
Evaluation
Initial evaluation of brachycephalic dogs should begin during routine physical examinations as puppies, with evaluation for stenotic nares, signs of stertor or stridor with restraint, and evidence of increased respiratory effort during the examination. An early discussion with owners about signs of exercise intolerance, snoring, and labored breathing when the puppy is sleeping or playing at home is warranted. Respiratory rate, mucus membrane color, capillary refill time, and posture can be
Clinical Signs
Typical respiratory clinical signs may include stertor, stridor, snoring, coughing, exercise intolerance, increased respiratory effort, hyperthermia, and collapse.28, 29 Because BAS is a progressive disease, clinical signs can vary from minimal increase in respiratory effort to severe respiratory crisis due to airway closure and laryngeal collapse that requires emergent medical intervention. In addition to the common clinical signs seen in awake animals, suffocation may also occur during sleep
Gastrointestinal Complications
Gastrointestinal complications typically found in dogs with BAS include frequent vomiting, regurgitation, and ptyalism.30 Hiatal hernia and pyloric stenosis have also been described in dogs with BAS.31, 32 In addition, endoscopic and histologic changes can be found. One study of 73 brachycephalic dogs, all with 1 or more upper respiratory tract abnormalities (stenotic nares, elongated soft palate, laryngeal collapse, or other), 97.3% of dogs had esophageal, gastric, or duodenal abnormalities
Systemic Complications
Additional medical complications owing to skull confirmation in brachycephalic dogs include skin fold dermatitis, malocclusion, hydrocephalus, and facial nerve paralysis.33, 34 Globe proptosis owing to a shallow orbit is not an uncommon complication from excessive restraint or mild trauma.35 In addition, pigmentary keratitis is common in brachycephalic dogs and may have an early-onset congenital predisposition in some breeds (Pekingese and Pugs).35
Brachycephalic dogs have been shown to have
Medical
The mainstay of medical management for dogs with brachycephalic airway disease is weight management. Studies have shown a correlation between elevated BCS and the severity of respiratory distress associated with BAS12; however, in other studies, a significant correlation was not observed.3 Despite these conflicting studies, weight management should be stressed with brachycephalic dog breed owners from the time of puppyhood.
In addition, activities that increase panting and respiratory effort
Conclusion
To some degree BAS is a common finding in most brachycephalic dogs. Early intervention, even as young as 3-4 months of age, should be considered to decrease progression of the disease and life-threatening laryngeal collapse. Early surgical correction of stenotic nares and elongated soft palates has been shown to have very favorable long-term outcomes with minimal risk to the patient.3 In advanced cases of increased airway resistance and laryngeal collapse, surgical correction may still be
References (50)
Airway physiology
Vet Clin North Am Small Anim Pract
(1992)Brachycephalic airway syndrome
Vet Clin North Am Small Anim Pract
(1992)- et al.
Upper airway obstruction: general principles and selected conditions in the dog and cat
Vet Clin North Am Small Anim Pract
(1985) - et al.
Environmental skin diseases
Stϋtz und Bewegungsapparat
- et al.
Brachycephalic syndrome in dogs
Compend Contin Educ Pract Vet
(2003) - et al.
Surgical correction of brachycephalic syndrome in dogs: 62 cases (1991-2004)
J Am Vet Med Assoc
(2007) - et al.
Craniofacial angle in dolicho-, meso- and brachycephalic dogs: radiological determination and application
Ann Anat
(1993) - Evans HE: Miller’s Anatomy of the Dog, (ed 3). Philadelphia, WB Saunders,...
- et al.
Passiver bewegungsapparat, skelettsystem
Scha¨delformen beim Hund
Zbl Vet Med C Anat Histol Embryol
Surgery of the upper respiratory system
Laryngeal collapse in seven brachycephalic puppies
J Small Anim Pract
Technique and outcome of nares amputation (Trader's technique) in immature Shih Tzu's
J Am Anim Hosp Assoc
Prevalence of gastrointestinal tract lesions in 73 brachycephalic dogs with upper respiratory syndrome
J Small Anim Pract
Long-term results of upper respiratory syndrome surgery and gastrointestinal tract medical treatment in 51 brachycephalic dogs
J Small Anim Pract
Nasopharyngeal turbinates in brachycephalic dogs and cats
J Am Anim Hosp Assoc
Brachycephalic syndrome
Semin Vet Med Surg (Small Anim)
Bronchial abnormalities found in a consecutive series of 40 brachycephalic dogs
J Am Vet Med Assoc
Brachycephalic airway obstructive syndrome in dogs: 90 cases (1991-2008)
J Am Vet Med Assoc
Upper airway obstruction surgery:1, stenotic nares surgery in brachycephalic dogs
J Am Anim Hosp Assoc
Results of surgical correction of abnormalities associated with brachycephalic airway obstruction syndrome in dogs in Australia
J Small Anim Pract
Resection of the soft palate in the dog
J Am Vet Med Assoc
Upper airway obstruction surgery: 2, soft palate resection in brachycephalic dogs
J Am Anim Hosp Assoc
Brachycephalic airway obstructive syndrome
Probl Vet Med
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2022, Veterinary Clinics of North America - Small Animal PracticeCitation Excerpt :Additional respiratory function testing and scoring to document the severity of BOAS can be performed. Snoring, inspiratory dyspnea, exercise intolerance, sleep disturbances, cyanosis, and, in the most severe cases, syncopal episodes are most often reported by owners.2,4,83,85,94,101–103 On inspection, stenotic nares and inspiratory efforts with even abdominal breathing can be observed.
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2022, Veterinary Clinics of North America - Small Animal PracticeCitation Excerpt :Cardiac troponin 1 levels were elevated in a majority of brachycephalic dogs in 2 reports.37,38 Given the grave implications of chronic upper airway obstruction, surgery is indicated to correct primary abnormalities early in life to improve quality of life and prevent development of secondary changes.11,13,22 Traditional surgical intervention of BOAS has focused on widening the external nares, shortening the soft palate, and excising everted mucosa of the laryngeal ventricles.3,9,13,19,20
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2021, Computers in Biology and MedicineCitation Excerpt :Therefore, further investigation of impaired air conditioning in BOAS-affected bulldogs is required. Over time, the primary component of BOAS (stenotic nares) weakens more rigid structures nearby and can eventually lead to secondary changes such as palate and laryngeal edema, saccule and tonsil eversion, and laryngeal collapse [6]. Therefore, surgical intervention is necessary to improve ventilation through the nasal route and prevent further negative secondary effects.