Airway sampling PRACTICAL

Question 1

Explain the process and how the epilgotts, soft palate and artenoids change when the horse swallows?

Answer 1

1. Food bolus moved caudally by tongue
2. Base of tongue pushes bolus caudally and dorsally
3. Soft palate elevates to allow bolus to move dorsally from the oropharynx to nasopharynx
4. Epiglottis retroverts (to cover the tracheal opening) with simultaneous adduction of arytenoid cartilages to close the laryngeal opening
5. Oesophageal sphincter relaxes to accept the bolus
6. Oesophagus contracts rostral to bolus and primary peristaltic waves carry bolus to cardia

Question 2

Explain the process and how the epilgotts, soft palate and artenoids change when the horse breathes?

Answer 2

1. Horse is an obligate nasal breather - cannot breathe through its mouth
2. Soft palate lies ventrally with epiglottis just overlying the caudal edge
3. Arytenoid cartilages remain dorsal to cover the opening to the oesophagus

Question 3

What is the process of performing a broncho-alveolar lavage?

Answer 3

1. Sedation
2. Extend head
3. Pass down trachea

• Opposite to NGT: would flex head and pass down oesophagus

1. Feed down as far as you can
2. Inflate cuff with air or saline/water

• Isolates section of lung

1. Inject 250-300ml saline and withdraw ~70%
2. Lavage cells for lab for cytology

• Differential count - proportion of different cells
• e.g. neutrophils:
  
  • 5-10% = normal
  • 10-20% = mild asthma
  • >25% = severe asthma
• On lavage would expect fluid with mucus and soapy surfactant at the top - without this could be due to a cough and being in the wrong place (therefore inject LA before to avoid cough from irritation)

Question 4

What can samples from a broncho-alveolar lavage be used for?

What can the samples not be used for and why?

Answer 4

• Samples can be taken for cytology
• Not sterile - so cannot be used for pathology
• Good for confirming diagnosis e.g. asthma

Question 5

How can you perform a trans-tracheal wash and what can samples be used for?

Answer 5

• Can be done endoscopically through catheter
  
  • Easy
  • Most common in practice
• Sample taken from tracheal bifurcation
• 20-30ml saline injected and withdrawn
  
  • Used for cytology and patholgy

Question 6

What are the different types of catheter that can be used for a trans-tracheal wash?

Answer 6

• Single lumen - for cytology, not pathology as can contaminate
• Triple lumen - one catheter inside another inside another, central catheter is therefore sterile
  
  • Expensive
  • Not contaminated
  • Sterile

Question 7

Explain how you can perform a blind trans tracheal wash?

Answer 7

1. Measure catheter to lower part of airway to ensure you know how far to go in
2. Clip, scrub, LA
3. Feel tracheal rings and go in between the cartilages
4. Push whole thing into trachea
5. Remove stylet
6. Insert catheter in

• Risk of emphysema