Respiratory pathology 2 Flashcards
Give 2 examples of developmental abnormalities associated with the larynx and trachea
- Hypoplastic trachea (often in young brachycephalic dogs)
- Tracheal collapse (miniature and toy breeds affected)
What are the consequences of a hypoplastic trachea?
- Don’t have enough airflow to support the body size
- Decreased tracheal lumen diameter causes highly increased resistance
- Dyspnoea (breathing difficulty)
- Exercise intollerence
How does laryngeal paralysis differ in dogs and horses?
Horses - unilateral, primarily on the LHS
Dogs - bilateral
What are some of the causes of laryngeal paralysis?
- idiopathic neuronal degeneration
- congenital abnormality
- toxins
- compression or irritation of the nerve (neoplasia, trauma, disease)
What results from damage to the recurrent laryngeal nerve, how does this affect inspiration?
- Atrophy of cricoarytenoids muscles
- Failure of one or both of the arytenoid cartilages to abduct during inspiration
Atrophy of the left cricoarytenoid muscle causes what disease in horses?
Equine laryngeal hemiplegia (roaring)
Describe how Equine laryngeal hemiplegia (roaring) affects the airway
Flaccid left arytenoid cartilage and vocal cords are sucked into the airway causing a roaring noise
How does laryngeal oedema occur?
Fluid exudate from blood vessels causes swelling of the larynx
What are some of the causes of laryngeal oedema?
- Local trauma e.g. intubation
- Irritants
- Acute respiratory infections
- Allergic reactions
What are the causes of laryngitis/tracheitis (inflammation)?
- infectious agents
- trauma
- irritants
- parasites
What can be seen grossly on the tissue as signs of laryngitis/tracheitis?
- mucosal hyperaemia
- oedema
- ulceration
- serous or catarrhal exudate
Laryngeal necrobacillosis has what affects on the body and how does it affect the animal?
- ulcerative necrosis of the larynx
- death due to toxaemia, asphyxiation and aspiration pneumonia
Give examples of anatomical factors that render the bronchioles vunerable
- lack of supporting cartilage
- few cilia and no mucus
- clara cells are metabolically active and can produce reactive metabolites
Give examples of causes of acute bronchitis and bronchiolitis
- infectious agents
- irritants
- allergens
- foreign bodies
- parasites e.g. Dictyocaulus viviparus
Overall the acute inflammatory reaction is similar to the upper airways, but what can happen in addition to this in the bronchi/bronchioles?
Severe bronchiolitis can cause bronchiolitis obliterans
Describe bronchiolitis obliterans and how it becomes obstructive
- Results in loss of epithelium and attachment of exudate to the basement membrane
- epithelium repairs around the exudate
- exudate is infiltrated by WBCs and fibroblasts (which lay down fibrous tissue and collagen) to form a polyp
- Polyp becomes covered in epithelium leaving a permanent obstructive lesion in the bronchiolar lumen
What are the 3 possible causes of chronic bronchitis and bronchiolitis?
- Chronic or repeated infections
- Parasitic disease
- Allergic disease
How does chronic bronchitis and bronchiolitis lead to an increase in mucus production?
- Bronchial goblet cell hyperplasia
- Bronchial gland hyperplasia
- Goblet cell metaplasia in bronchioles
How does chronic bronchitis and bronchiolitis lead to thickening of the mucosa?
- Bronchial gland hyperplasia
- Epithelial hyperplasia and metaplasia
- Smooth muscle hyperplasia around airways
- Inflammatory cells and fibrosis
What are the two main outcomes in the airways of chronic bronchitis and bronchiolitis?
- Increased mucus production
- Thickening of the mucosa
How is partial / complete obstruction of airways clinically reflected?
- Difficulty breathing
- Cough
- Increased respiratory noise
- Collapse
- Reduced blood oxygenation
What is bronchiectasis?
- Obstruction of the lumen by exudate – mucus stays in the airways
- Inflammatory cells release their lysosomal enzymes which cause damage to the bronchiole wall
- Necrosis of the bronchial wall causes permanent dilation of the bronchus
Give 2 examples of conditions causing chronic bronchitis + bronchiolitis
- Cattle lungworm = Dictyocaulus viviparus
- Equine recurrent airway obstruction
How does cattle lungworm cause chronic bronchitis and bronchiolitis?
- larval migration through the alveoli can cause acute pneumonia and blockage of the bronchioles with exudate
- Adult worms in the bronchi cause irritation, increased mucous production and thickened mucous
How does Equine recurrent airway syndrome cause chronic bronchitis and bronchiolitis?
Asthma like condition, immune mediated hypersensitivity reaction (type III) to inhaled allergens in mouldy hay
How are the bronchioles affected in equine recurrent airway obstruction?
- increase mucus
- mucosal thickening
- peribronchial fibrosis
- bronchospasm
What are the clinical signs of equine recurrent airway obstruction?
- Cough
- Mucopurulent exudate
- Exercise intolerance
- Forceful expiration => abdominal muscle hypertrophy
