Upper respiratory tract disease Flashcards
Describe how selective breeding has caused Brachycephalic obstructive syndrome
Selective breeding has led to the skull becoming greatly shortened without a corresponding reduction in the volume of soft tissues, leading to upper airway obstruction, inspiratory effort and marked negative pharyngeal and laryngeal pressures on inspiration
What are the consequences of a shortened skull?
- Overlong soft palate
- Stenotic nares
- Tracheal/laryngeal hypoplasia
- Pharyngeal collapse, excessive turbinates
Describe the secondary changes of Brachycephalic obstructive syndrome
- Everted laryngeal saccules
- Tonsillar enlargement/protrusion
- Laryngeal collapse (eversion of the laryngeal saccules then progressive medial deviation of the corniculate and cuneiform processes of the arytenoid cartilages).
- Tracheal collapse
What are the clinical signs of Brachycephalic obstructive syndrome
- Inspiratory stertor
- Dyspnoea
- Snoring / sleep apnoea
- Exercise intolerance
- Cyanosis
- Fainting / collapse
- Gagging / dysphagia
- Regurgitation
- Cough, pyrexia, dullness with aspiration
What is inspiratory stertor?
Snoring noise, deep, low pitch, reverberates in the upper airway
How is Brachycephalic obstructive syndrome diagnosed?
- Signalment and clinical signs
- Examination of airway: tonsils, soft palate, larynx
- Radiography: pharynx/neck, thorax
How can Brachycephalic obstructive syndrome be diagnosed?
- Surgical modification of airway
- Decide whether to perform surgery based on severity of clinical signs
Which surgical treatments can be performed for BOAS?
- Rhinoplasty: lateral, vertical or horizontal wedge resection of the dorsal lateral nasal cartilages
- Palatoplasty
- Laryngeal sacculoectomy
- Tonsillectomy
Describe emergency stabilisation of a BOS pateint
- Cool, quiet environment
- Supplementary oxygen
- Sedation
- Intravenous corticosteroids
- Anaesthetise and intubate if required
Describe stage 1 of laryngeal collapse
Eversion of laryngeal saccules
Describe stage 2 of laryngeal collapse
Eversion of the laryngeal saccules and medial deviation of the cuneiform process of the arytenoids
Describe stage 3 of laryngeal collapse
Eversion of the laryngeal saccules and medial deviation of the cuneiform and corniculate processes of the arytenoid cartilage
How can laryngeal collapse be treated?
Stage 1 - laryngeal sacculectomy
Stages 2 and 3 - laryngeal sacculectomy +/- arytenoid caudolateralisation
Permanent tracheostomy
What is laryngeal paralysis?
Failure of dorsal cricoarytenoid muscle to abduct arytenoid cartilage on inspiration
-> Reduced glottis size and increased airway resistance
Which nerve is affected in laryngeal paralysis?
Recurrent laryngeal nerve
What are some causes of laryngeal paralysis?
- Metabolic neuropathy: hypothyroidism, myasthenia gravis
- Generalised myopathy
- Damage to recurrent laryngeal nerve: trauma, neoplasia or other space-occupying lesion
- Most cases are idiopathic
Which breeds are most likely to acquire laryngeal paralysis?
Golden retrievers, Labradors, Irish setters, Afghan hounds
What are the clinical signs of laryngeal paralysis?
- Inspiratory stridor
- Exercise intolerance
- Fainting / collapse
- Altered phonation: change in pitch or loss of bark
- Cough / gagging during swallowing
- Dysphagia
How can laryngeal paralysis be diagnosed?
- History and clinical signs
- Laryngoscopy to assess laryngeal function
- Thoracic / cervical radiographs: look for mass lesions and concurrent aspiration
- Blood tests: rule out metabolic disease
- Electromyography / nerve and muscle biopsy
- Edrophonium response test: if myasthenia gravis is suspected
Describe normal and abnormal laryngeal function
- In a normal dog the arytenoid cartilages abduct during inspiration and adduct during expiration
- Failure of the arytenoids to abduct during inspiration indicates laryngeal paralysis
- Paradoxical movement of the arytenoids can occur where they are pulled medially by reduced airway pressure during inspiration and passively abduct during expiration
How is laryngeal paralysis treated?
Left arytenoid lateralisation: easier than right, unilateral gives adequate airway
What are some complications associated with arytenoid lateralisation?
- Aspiration pneumonia
- Failure of tieback
- Seroma
- Development of other signs of neuropathy
How is tracheal disease investigated on clinical exam?
- Auscultation
- Palpation of the cervical trachea may reveal changes in shape of the trachea e.g. in tracheal collapse or elicit a cough if the tracheal mucosa is inflamed.
What are some other investigative methods for tracheal disease?
- Diagnostic imaging
- Tracheobronchoscopy
- Biopsy
- Tracheal wash and bronchioalveolar lavage for bacterial culture and sensitivity testing and cytology
