Diagnostic approach to equine respiratory system Flashcards
What are the 3 categories of stimulants to irritant receptors?
*Physical
*Chemical
*Inflammation
What are the Physical irritants?
*Foreign material
*Turbulent air
*Mucus
What are the chemical irritants?
*Osmolarity
*Irritant
What are the presenting signs of LRT disease?
1.Coughing
2.Bilateral nasal discharge
3. Tachypnoea / Dyspnoea
what is the pathogenesis of bilateral nasal discharge?
1.Airway inflammation
2.Increase mucus production + Altered mucus composition
3.Mucopurulent bilateral nasal discharge
What causes increased resp rate + effort?
- Hypercapnia, Acidaemia + Hypoxaemia
- Aortic, Carotid + medulla chemoreceptors triggered
3.Respiratory centre in medulla activated
What % of maximal oxygen consumption does a horse use at rest?
4%
What history knowledge should you find out about the horse?
- Disease time course and features
- Herd or individual problem
- Age and use of horse
- Management and environment
- Coexisting problems
What observations should you do to a horse from a distance regarding LRT?
- Posture (extended head and neck = severe respiratory distress)
- Abdominal effort
- Respiratory Rate
- Respiratory Depth –
- Pattern – biphasic?
- Hypertrophy of Ext. ab. oblique
– ‘Heave line’
What part of the respiratory tract is more likely to collapse on inspiration?
Upper respiratory tract
What part of the respiratory tract is more likely to collapse on expiration?
Lower respiratory tract
If doing a general clinical exam what should you examine?
- All systems
- Temp / Heart rate
- Ventral oedema?
- Guttural Pouches & Lymph nodes
– enlargement, discharges - Nares and Nasal Passages
– airflow obstruction
– discharges
What happens during inspiration dysponea?
*Intercostals sucked in
*Wheezing sound
*Inwards pressure on tube of URT = collapse
What is a normal breath sound in a horse?
= turbulent air in large (>2mm) airways
*Soft blowing sound
*Inspiration > expiration
*Faster air = louder
*Low frequency sounds travel best through normal lung
Where should you auscultate a horse?
*Bottom of trachea
*Centre of chest - where sound should be loudest
*Then move around the thoracic cavity
What are abnormal adventitious breath sounds?
- Wheezes
- Crackles
- Pleural rubs
- Cough
- Expiratory Grunts/groans
What is a wheeze?
Airway narrowing and vibration
What causes a wheeze?
Thickened wall – oedema / inflammation
Intraluminal obstructions – e.g. mucus /foreign body
Bronchospasm
Extra luminal compression
What are the 2 different types of crackles?
- Coarse crackles
- Fine crackles
What causes a coarse crackle?
Bubbling mucus
Inspiration or expiration
Radiate widely
What causes fine crackles?
Popping open of collapsed small
airways
Most common: early inspiration
What causes pleural friction rubs?
- Inflamed parietal and visceral pleural membranes rubbing
together
What would you use for thoracic percussion?
*Pleximeter
*Plexor
What are further tests you could take for the respiratory system?
- Laboratory and Clinical Pathology
- Nasopharyngeal swab
- Endoscopy and transendoscopic tracheal aspirate
- Percutaneous tracheal aspirate
- Bronchoalveolar lavage
- Thoracocentesis
- Imaging
– Radiography
– Ultrasonography - Lung biopsy
What are LRT samples you can take to test for disease?
- Tracheal aspirate (TA)
- Bronchoalveolar Lavage (BAL)
- Thoracocentesis
What are the advantages of transendoscopic tracheal aspirate?
- easy
- non-invasive
- sample representative of
whole lung
What are the disadvantages of transendoscopic tracheal aspirate?
- sample contaminated by
nasopharyngeal flora and
equipment - Specialist equipment required
What are the advantages of transtracheal aspirate?
- no pharyngeal contamination
- no specialised equipment
- useful in young foals when
endoscopes too large
What are the disadvantages of transtracheal aspirate?
- Horse may cough catheter into
pharynx and contaminate sample - invasive
– cellulitis
– subcutaneous emphysema
What cells are abnormal and what is an abnormal neutrophil count with a tracheal aspirate sample?
– Abnormal = >20% neutrophils
– Abnormal = Presence of mast cells, eosinophils
What is bronchoalveolar lavage? What is it good/not so good for?
- Small area of distal airway lavaged with saline
– best for diffuse lung disease - Good for cytology
- Unsuitable for bacteriology
What are the advantages of bronchoalveolar lavage?
- sample obtained from DISTAL airways =
most commonly affected - Best correlation with pulmonary function and histopathology
- equipment cheap and accessible (unless endoscopically obtained)
What are the disadvantages of bronchoalveolar lavage?
- Site may not be appropriate in animals with
– localised pulmonary abscesses or
pneumonias (cranioventral lobes) - Pharyngeal contamination
– Culture not useful - Invasive
What is the best way to diagnose asthma?
BAL - bronchoalveolar lavage
When would you use BronchoAlveolar Lavage / Tracheal Aspiration?
BAL: better correlation with:
* Airway obstruction (pulmonary function testing)
* Exercise induced hypoxaemia
* Lung histopathology
TA is most useful for
* Bacteriology
* Focal lung lesions e.g. Abscess/neoplasia
* Tracheal inflammation
