Brachycephalic Obstructive Airway Syndrome (BOAS) Overview

Definition

Brachycephalic Obstructive Airway Syndrome (BOAS) is a serious condition primarily affecting brachycephalic (short-faced) dog breeds. It occurs due to anatomical changes that lead to partial or complete airway obstruction, significantly impacting their ability to breathe and leading to various health issues.

Popular Breeds Affected

• English Bulldog (AKC 4th)

• French Bulldog (AKC 6th)

• Boston Terrier (AKC 21st)

• Pugs (AKC 32nd)

• Pekingese (AKC 93rd)

• Shih Tzu (AKC 44th)

Clinical Signs of BOAS

Common Symptoms:

• Snoring: Most prevalent during sleep due to obstruction.

• Apnea: Temporary cessation of breathing, particularly during sleep or physical activity.

• Inspiratory Dyspnea: Difficulty in inhalation, resulting in distressful breathing patterns.

• Exercise Intolerance: Reduced ability to engage in physical activity, especially in heat or high-stress environments.

• Stridor: A high-pitched wheezing sound resulting from airflow obstruction.

• Cyanosis: Bluish discoloration of the skin and mucous membranes due to hypoxia (lack of oxygen).

• Collapse: Severe cases may result in sudden weakness or loss of consciousness during exertion.

Symptoms Worsen After:

• Exercise: Increased physical activity heightens respiratory demands.

• Heat: Elevated temperatures exacerbate airway constriction and result in physiological stress.

• Stress: Anxiety or panic can worsen respiratory function.

Signalment:

The disorder is more commonly seen in dogs aged 1-3 years, although it can present in older dogs. Males tend to be affected more frequently than females, highlighting potential genetic predispositions.

Anatomical Features Contributing to BOAS

Airflow Obstruction Mechanisms:

• Constricted Nasal Passages: Narrowed nares increase the resistance to airflow.

• Elongated Soft Palate: Excessive length can obstruct the airway during breathing.

• Aberrant Nasal Turbinates: Irregular or malpositioned turbinate structures can interfere with airflow.

• Redundant/Hypertrophied Nasopharyngeal Tissue: Excess tissue contributes to blockage in the pharyngeal area.

• Macroglossia: Enlarged tongues in brachycephalic breeds can further obstruct the airway.

• Tracheal Hypoplasia: An underdeveloped trachea limits airflow capacity and resistance.

Pathophysiology and Consequences

The persistent obstruction leads to increased airflow resistance, which triggers:

• Inflammation: Ongoing irritation to airway structures.

• Swelling of Tissues: Can lead to further narrowing of air passageways.

• Weakening of Airway Structures: Prolonged strain can impair the integrity of respiratory returns. This cycle exacerbates the risk for brachycephalic dogs, necessitating medical intervention in many cases.

Secondary Problems Associated with BOAS

Progressive Changes:

• Everted Laryngeal Saccules: Tissue protrusion that can significantly obstruct airflow.

• Everted Tonsils: Swelling can lead to further airway blockage.

• Mucosal Edema: Swelling of the lining of the airways.

• Laryngeal Collapse: Progressive narrowing based on severity (Stages I, II, and III). Approximately 75% of affected dogs may also experience gastrointestinal diseases, often due to stress and distress from restricted breathing.

Diagnostic and Emergency Management

Diagnostics for BOAS:

• Thoracic Radiographs: Useful for assessing lower airway and identifying major obstructions.

• CT Scan: Provides detailed imaging for anatomical assessment and surgical planning.

Emergency Management:

• Sedation: Medications such as Butorphanol and Acepromazine help to reduce anxiety and distress.

• Oxygen Therapy: Administered to improve oxygen saturation levels in severe cases.

• Cooling Measures: Techniques like ice baths and fans are vital for overheating dogs.

• Anti-inflammatory medications: Dexamethasone may help reduce swelling and inflammation. In critical cases, intubation or a temporary tracheostomy might be necessary to secure the airway.

Surgical Interventions

Indications for Surgery:

Surgical interventions are considered for dogs with:

• A history of significant airway obstruction.

• Gastrointestinal signs linked to BOAS symptoms.

Types of Surgeries:

• Alarplasty: Surgical modification of the nares to widen the nasal passages.

• Palatoplasty: Correction of the elongated soft palate.

• Resection: Removal of everted saccules and tonsils to improve airflow.

• Novel Techniques: Such as laser-assisted turbinectomy can provide less invasive options with faster recovery.

Postoperative Recovery and Monitoring

Recovery Protocols:

• Administer oxygen post-surgery and monitor recovery closely.

• Watch for complications, including swelling, respiratory distress, and recurrence of obstruction.

Long-term Changes:

• Owners should adjust lifestyle, avoiding excessive heat and maintaining a lean body condition to reduce the risk of further complications.

Client Education and Advocacy

Owner Responsibilities:

Educating owners on recognizing early signs of respiratory distress in their dogs is crucial. They must advocate for their pets' health needs and ensure a supportive environment that limits stressors.

Common Misconceptions:

Many owners underestimate the severity of BOAS symptoms, often viewing snoring as benign. It is critical for them to be proactive in health assessments to ensure their dogs receive appropriate care.