Endo-tracheal Intubation

Question 1

What are the advantages of ET intubation?

Answer 1

• Maintains airway
• Prevents aspiration pneumonia
• Prevents Laryngospasm (especially in cats)
• Reduces environmental pollution
• Allows IPPV
• Frees a person who otherwise would be holding a mask
• Allows easier access to face and mouth by VS/RVN
• Reduces mechanical dead space

Question 2

How long should an ET tube be?

Answer 2

From incisor/canine tooth to the thoracic inlet/spine of scapula. And compare to palpable width of the trachea

Question 3

What equipment do you need for ET intubation?

Answer 3

Selection of ET tubes
Tube tie
Mouth Gag
Syringe to inflate cuff
Lubricant
Laryngoscope
Local Anaesthetic spray (especially in cats!)
Assistant

Question 4

Describe the 3 types of ET tube

Answer 4

1. Rubber
   - low volume, high pressure cuff (more likely to cause tracheal damage)
2. PVC
   - transparent
   - high volume, low pressure cuff (less likely to cause damage such as tracheal necrosis or rupture - as evenly distributed pressure)
3. Silicone
   - straight
   - commonly used in exotics

Question 5

What is a Murphy eye? What is its purpose?

Answer 5

Hole in the bevelled end of an ET tube near the cuff. Common feature of PVC tubes.
Safety feature: allows movement of gas even if end is blocked e.g. lodged against bronchus wall

Question 6

What safety checks should be carried out on an ET tube?

Answer 6

• ensure correct size
• ensure clean and free from blockage, and has been well-rinsed
• ensure cuff is operational
• ensure not damaged, perished and in-date

Question 7

What is the GUIDELINE tube size for a Cat?

Answer 7

4-4.5

Question 8

What is the GUIDELINE tube size for a dog 10kg? 20kg? 30kg?

Answer 8

10kg - 8
20kg - 10
30kg - 12

Question 9

What is the difference between a MacIntosh and Miller laryngoscope blade?

Answer 9

A MacIntosh is curved and a Miller is straight

Question 10

Describe the process of intubation

Answer 10

• Get assistant to restrain patient
• Ensure the anaesthetic depth is adequate
• Visualise the glottis using a laryngoscope to depress the base of the tongue
• Insert the tip of the bevel of the tube and the rotate to follow the curve of the trachea
• Use topical local anaesthetic if required
• Check placement of the tube and inflate cuff if required

Question 11

Describe the ways of checking ET tube placement

Answer 11

• Palpate the tube within the trachea
• Auscultate both lung fields (should be able to hear air movement in both lungs - this check its not too far in and just in one lung)
• Observe movement in reservoir bag
• Check for air movement in tube (condensation in tube or hold cotton at end of tube)
• Gold standard - use a capnograph (tells us that CO2 is being produced)

Question 12

What are the disadvantages of intubation?

Answer 12

• Increased airway resistance if the tube is too narrow
• Kinking or occlusion of the tube leading to complete respiratory obstruction
• Iatrogenic trauma to the larynx ( especially in cats. Can also damage cilia and cause future problems)
• Irritation to mucosa if tube not rinsed properly
• Over inflation of cuff leading to tracheal damage
• Endo-bronchial intubation -> misplacement

Question 13

What should be done in patients that are anticipated to be tricky to intubate?

Answer 13

Pre-o2 patients for at least 5 mins prior

Question 14

What would indicate that the ET tube was in the oesophagus?

Answer 14

Patient doesn’t stay asleep
Low SPO2 on pulse ox
No/very little movement of reservoir bag

Question 15

What would indicate that the ET tube was in the bronchus?

Answer 15

SPO2 greatly reduced
Unilateral breath sounds
Patient wakes up

Question 16

What should you do to help combat laryngospasm in cats?

Answer 16

Pre O2
Use one spray of LA and wait
Use a laryngoscope

Question 17

What would indicate the ET tube is blocked?

Answer 17

SPO2 very low
Little movement of reservoir bag
Cyanosis

Question 18

What would suggest that there’s been a tracheal rupture?

Answer 18

Sub-cutaneous emphysema

Question 19

What must be done before re-positioning a patient?

Answer 19

Disconnect the tube!

Question 20

When should patients be extubated?

Answer 20

In normal dogs, once pharyngeal reflexes have returned e.g. swallow reflex.
In cats, earlier to avoid laryngospasm - when ear flick reflex returns.
In brachycephalic breeds, those with megaoesophagus, or those give NMBAs that have not been reversed - want to extubate later! When cough/chews.

Question 21

What device can be used in cats and rabbits for intubation? Why would you use this?

Answer 21

V-gel supraglottic airway device
- doesn’t touch the trachea therefore doesn’t cause any damage. It enters the top of the oesophagus to seal the airway.
You would need a capnograph if using this!

Question 22

What should be used to clean ET tube?

Answer 22

Non-irritant substances e.g. Endoscope cleaning solution. Rinse thoroughly!!
Can also use cold chemical sterilisation