Managing brachycephalic obstructive airway syndrome

Brachycephaly is a breed conformation that consists of short and wide skull proportions.¹ The short and wide conformation of the skull results in compression of the nasal and laryngeal airways, which may lead to reduced or absent frontal sinuses, aberrant nasal turbinates, and a reduction in overall airway space caused by a lack of alteration in the local soft tissue structures. The tongue, tonsils, soft palate, and nasopharyngeal mucosa are proportionally larger than the space within which they are housed, reducing the area for airflow through the upper respiratory tract.¹

Despite these conformational changes, not all brachycephalic dogs will be affected by brachycephalic obstructive airway syndrome (BOAS). Breeds with more severe brachycephalic conformation, including French bulldogs, pugs, and other bulldog breeds, are at greatest risk.^1-3 BOAS is a spectrum of disease characterized by multilevel, partial, or complete obstruction of the upper airway secondary to brachycephalic anatomic conformation and progressive secondary changes to the local anatomy.^1,3

The primary anatomic components of BOAS include the following^1,3:

• Stenotic nares
• Elongated and hyperplastic soft palate
• Hypoplastic trachea
• Aberrant nasal turbinates

The secondary anatomic components of BOAS include the following^1,3:

• Everted laryngeal saccules (stage 1 laryngeal collapse)
• Hiatal hernia
• Everted tonsils

BOAS primarily affects the respiratory system, with secondary consequences to the gastrointestinal system.^1,3 A less commonly considered consequence of BOAS is sleep-related disorders, particularly obstructive sleep apnea, which can impact overall quality of life.⁴

Clinical signs of BOAS include stertorous breathing, snoring, stress, heat and exercise intolerance, regurgitation, sleep disturbances, and, in extreme circumstances, respiratory distress, collapse, and cyanosis.^1,3 These clinical signs result from the overall reduction in airway diameter because of the brachycephalic conformation. Stenotic nares and aberrant nasal turbinates reduce the size of the nasal passages, making movement of air through the nasal cavity challenging, which often results in open-mouth breathing.^1,3 Movement of air through the nasal passages is important for thermoregulation, making these animals prone to hyperthermia.^1,3 The elongated and hyperplastic soft palate extends across the rima glottidis, resulting in a reduction in upper airway diameter, thus increasing the negative pressure required for air to pass. The increased negative airway pressures can result in eversion of the laryngeal saccules and tonsils locally but also result in increased negative pressure within the thoracic cavity, leading to gastroesophageal reflux and, in severe circumstances, hiatal hernias.^1,3 The hypoplastic tracheal component of this disease may exacerbate the respiratory signs but likely plays a lesser role in the airway obstruction.³

Many dogs exhibit mild signs such as stertor or snoring early in life, which many owners may consider normal for the breed. It is important to begin discussing BOAS early in these animals’ lives, so that owners can better understand the consequences of the disease and monitor for progression of clinical signs. Early intervention when clinical signs are mild is ideal, as the longer the upper airway tissues are exposed to increased upper airway pressures, the more affected they become (ie, further hyperplasia, redundancy, and eversion of local soft tissues), leading to more severe clinical signs.^1,3

Diagnostic evaluation for BOAS can vary greatly based on the severity of clinical signs, the disease’s chronicity, and the surgeon’s preferences. Stenotic nares are easily identified on routine physical examination; however, further investigation of the nasal passages for aberrant nasal turbinates requires advanced imaging such as a CT scan or rhinoscopy.^1,3 Evaluation of the palate, laryngeal saccules, tonsils, and other nasopharyngeal tissues can be achieved with a sedated oral and laryngeal examination. This can be performed with or without endoscopic equipment. However, greater assessment of soft palate thickness and overall airway diameter can be achieved via CT scan.^1,3,5 Thoracic imaging (3-view thoracic radiographs or CT) can rule out aspiration pneumonia because of gastroesophageal reflux/regurgitation and can be used to assess for evidence of a hiatal hernia. Hiatal hernias can be dynamic in nature and therefore may not always be identified on static imaging.^1,3

Surgical interventions are typically aimed at the respiratory components of the disease, with the goal of reducing the negative pressures within the upper airway, thus improving air flow.1,3 By reducing the upper airway pressures, the negative intrathoracic pressures may also be improved, resulting in the improvement or resolution of gastrointestinal-related clinical signs. However, if gastrointestinal signs persist, medical management with antacids and promotility agents may be required, or direct surgical intervention for treatment of a hiatal hernia may be warranted.³

Surgical interventions may include any combination of the following procedures^1,3:

• Rhinoplasty for stenotic nares
• Partial staphylectomy for elongated and hyperplastic soft palate
• Laryngeal sacculectomy for everted laryngeal saccules
• Laser ablation turbinectomy for aberrant nasal turbinates
• Tonsillectomy for enlarged and everted tonsils

The individual dog’s anatomic abnormalities will determine the combination of procedures. Surgeon preference and experience will dictate the specific surgical techniques used to address each component of the disease.

Preoperatively, a brachycephalic risk score may be determined to understand the relative risk for a negative outcome following BOAS surgical interventions.⁶ This score can help set appropriate expectations for owners and inform the veterinary team of the individual risk for each dog undergoing surgical treatment for BOAS. In addition to the specific risk associated with airway surgery, brachycephalic dogs are at increased risk of complications associated with anesthesia.⁷ Preanesthetic interventions are recommended and often include medications used to reduce the risk of vomiting and regurgitation, as aspiration pneumonia is the most common complication following brachycephalic anesthesia.^7,8

In addition to aspiration pneumonia, the risk for postoperative upper airway obstruction following BOAS surgery is significant. There are many ways to reduce the risk of upper airway obstruction, such as administration of injectable steroids, topical application of mannitol in the oropharynx, and a slow and controlled anesthesia recovery. However, being prepared for an emergency temporary tracheostomy is always recommended.^3,8

Takeaway

The overall prognosis for dogs following BOAS surgery remains unclear because of the multilevel nature of the airway obstruction with this disease.^1,3 Overall, dogs who recover from BOAS surgery should show improvement in respiratory and gastrointestinal clinical signs. If clinical signs persist, further investigations and interventions may be warranted. It is important to note that not all components of BOAS may be addressed with surgical interventions; thus, a return to normal airway function (nonbrachycephalic breeds) is unrealistic.

REFERENCES

1. Ekenstedt KJ, Crosse KR, Risselada M. Canine brachycephaly: anatomy, pathology, genetics and welfare. J Comp Pathol. 2020;176:109-115. doi:10.1016/j.jcpa.2020.02.008
2. Tomlinson F, O’Neill E, Liu NC, Sargan DR, Ladlow JF. BOAS in the Boston terrier: a healthier screw-tailed breed? PLoS One. 2024;19(12):e0315411. doi:10.1371/journal.pone.0315411
3. Krainer D, Dupré G. Brachycephalic obstructive airway syndrome. Vet Clin North Am Small Anim Pract. 2022;52(3):749-780. doi:10.1016/j.cvsm.2022.01.013
4. Hynes JM, Menard JV, Lopez DJ. Quality of life improvement in 3 dogs with sleep-disordered breathing managed by permanent (crico)tracheostomy. Am J Vet Res. 2024;86(2):1-9. doi:10.2460/ajvr.24.09.0270
5. Stordalen MB, Bray S, Stringer F, Stonebrook C, Guilherme S, Bray JP. Awake 160-slice computed tomography for upper airway evaluation in 17 dogs. Vet Sci. 2024;11(8):342. doi:10.3390/vetsci11080342
6. Tarricone J, Hayes GM, Singh A, Davis G. Development and validation of a brachycephalic risk (BRisk) score to predict the risk of complications in dogs presenting for surgical treatment of brachycephalic obstructive airway syndrome. Vet Surg. 2019;48(7):1253-1261. doi:10.1111/vsu.13291
7. Gruenheid M, Aarnes TK, McLoughlin MA, et al. Risk of anesthesia-related complications in brachycephalic dogs. J Am Vet Med Assoc. 2018;253(3):301-306. doi:10.2460/javma.253.3.301
8. Hill M, Lepiz ML, Ida KK, Rutter C, Mankin KT, Dickerson V. Implementation of a standard perioperative protocol reduces postoperative respiratory distress events in dogs undergoing surgical correction of brachycephalic obstructive airway syndrome. J Am Vet Med Assoc. 2025;263(5):590-598. doi:10.2460/javma.24.09.0598