13. respiratory pathology III

what are consequences of disruption of air conduction in the larynx?

• dyspnea

• excessive breathing noise

  • stertor (low pitched)

  • stridor (high pitched)

• choking

• aspiration pneumonia

• voice change

• exercise intolerance

what is the cause of laryngeal hemiplegia in horses?

• damage to vagus nerve or recurrent laryngeal nerve (often left)

  • cause: idiopathic or secondary to direct nerve damage

what are the consequences of laryngeal hemiplegia? what clinical sign is observed?

• paralysis and eventual atrophy of cricoarytenoid muscles (dorsal and lateral)

  • → inability to adduct and abduct arytenoid cartilages

• “roaring”

what causes laryngitis in calves? (infectious; environmental)

• infectious agents

  • IBR (BHV-1)

    • causes initial damage → allows secondary infection

  • fusobacterium necrophorum (“calf diphtheria”)

• environmental

  • contact ulcers

what animals are most commonly affected by tracheal collapse?

• toy breed dogs

• ponies

describe the pathology of tracheal collapse. what regions of the trachea are affected? what clinical sign is associated?

• defect in tracheal rings → dorsoventral collapse of trachea with trachealis stretching

• may be segmental (cervical or thoracic) or diffuse

• clinical sign: dry, honking cough

causes of tracheitis in cattle

• IBR (BHV-1)

• (malignant catarrhal fever - MCF)

• chemical burn from drench

causes of tracheitis in horses

• equine influenza

• EHV-1

causes of tracheitis in dogs/cats

dogs

• canine infectious tracheobronchitis (“kennel cough”)

  • many agents may be involved → mainly, bordetella bronchiseptica

  • (canine parainfluenza, canine adenovirus-2, others)

• canine distemper (uncommon)

cats

• FHV-1

  • secondary bacterial infection (ex. pasteurella multocida)

causes of tracheal stenosis

• chronic tracheitis or trauma with scarring & fibrosis

  • ex. over-inflated ET tube cuff

• neoplasia (extraluminal or intraluminal) → rare

what is the difference between obstructive and restrictive pulmonary disease?

• obstructive → increased resistance to or blockage of airflow

• restrictive → characterized by limited lung inflation/expansion due to lung or thoracic cavity abnormalities

  • microscopically → anything that thickens alveolar septae

  • or

  • macroscopically, outside of lungs (ex. mass, fluid) that restricts inflation

what are examples of obstructive respiratory diseases?

• bronchitis / bronchiolitis

• asthma

• alveolar emphysema

• other airway obstruction

what are examples of restrictive respiratory diseases? (lung abnormalities & thoracic abnormalities)

• lung abnormalities

  • pulmonary fibrosis

  • interstitial edema / pneumonia / emphysema

• thoracic (non-pulmonary) abnormalities

  • thoracic deformities (e.g. pectus excavatum)

  • pleural effusion

  • pleuritis

  • intrathoracic masses

bronchitis / bronchiolitis pathology

• bronchitis and tracheitis often concurrent

• exudate in lumen can obstruct airways

• submucosal inflammation may narrow airway lumen

• reflex bronchoconstriction also reduces diameter

what is the result of bronchitis and bronchiolitis?

↑ resistance and ↓ alveolar ventilation

what general categories of infectious agents can cause bronchitis/bronchiolitis?

• viral

• bacterial

• parasitic

what are viral causes of bronchitis / bronchiolitis? describe pathology

• often same causes as tracheitis

  • cattle: BHV-1

  • cats: FHV-1

• usually necrotizing lesions, loss of epithelial cells + cilia → secondary bacterial infection

what bacteria is associated with bronchitis/bronchiolitis? what is its associated pathology?

• mycoplasma sp.: organisms associate with cilia

  • m. bovis, dispar (cattle)

  • (m. hyopneumoniae - pigs)

• continued neutrophil infiltration and submucosal lymphocyte proliferation

what causes chronic obstructive pulmonary disease (COPD) aka “heaves” in horses?

environmental antigens: fungal spores, hay dust

what are clinical signs of “heaves”?

• exercise intolerance

• coughing

• expiratory dyspnea

• external abdominal oblique hypertrophy (heave line)

gross pathologic findings of “heaves”

• lack of lung collapse when opening thorax

• mucus in bronchioles

• peribronchiolar fibrosis

what are potential outcomes of chronic bronchitis/bronchiolitis?

• bronchiolitis obliterans

• bronchiectasis

what is bronchiolitis obliterans?

• obstruction of bronchiolar lumen by connective tissue following severe damage to bronchioles and alveoli

  • healing by fibrosis

• blocks airflow to alveoli, reduces vital capacity

bronchiolitis obliterans sequence of events (pathogenesis?)

1. necrosis of epithelium with ulceration, delayed repair

2. exudate rich in fibrin and chemotaxins

3. macrophages, fibroblasts, endothelial cells proliferate

4. organization of exudate by granulation tissue

5. forms obstructive plug

what is bronchiectasis? what is it associated with?

• dilation of bronchi beyond normal diameter due to wall destruction

  • inflammatory cell-mediated damage to wall

• associated with chronic bacterial bronchitis

what are consequences of bronchiectasis?

• results in increased turbulence of airflow →

  • increased resistance

  • impaired mucociliary clearance

  • deeper penetration of lung by infectious agents

    • can develop deeper pneumonia