Airway Management

Question 1

Why is airway management important?

Answer 1

Allows delivery of oxygen and volatile anaesthetic agent to patient
Allows removal of carbon dioxide
Most anaesthetics cause respiratory depression so need monitoring
Patient will have loss of airway reflexes
Scavenging and environmental protection
Allows for IPPV
‘protects airway’ - prevents secretions entering trachea

Question 2

IPPV

Answer 2

Intermittent Positive Pressure Ventilation

Question 3

Hypoxia

Answer 3

Low oxygen concentration in tissues

Question 4

Hypercapnia

Answer 4

High CO2 concentration in blood

Question 5

Hypoxaemia

Answer 5

Low oxygen concentration in blood

Question 6

What are the methods of providing oxygen?

Answer 6

Oxygen cylinders (size E or J)
Oxygen Concentrators

Question 7

Which size of oxygen cylinder is bigger?

Answer 7

J - kept outside
E is smaller

Question 8

Pros of Oxygen concentrators

Answer 8

Extracts oxygen from environment - endless supply
More portable than cylinders

Question 9

Cons of oxygen concentrators

Answer 9

Need electrical power supply - will need a back up if power fails
90-95% pure oxygen not 100%

Question 10

How do you measure ET tube against patient

Answer 10

From nares to point of shoulder
Doesn’t need to go as deep in cats (just past larynx)

Question 11

Parts of an ET tube

Answer 11

Machine end - adapter
Radiopaque marker line
Murphy eye - safety feature
Cuff
pilot line/balloon

Question 12

Types of ET tube

Answer 12

Red rubber
Clear PVC
Armoured Tubes
Cole Tubes

Question 13

What is important about intubating cats?

Answer 13

Spray lidocaine over larynx - prone to laryngospasm
Tube doesn’t need to go as deep as in dogs
Careful inflating cuff - prone to tracheal rupture

Question 14

Pros of Red Rubber Tubes

Answer 14

Good seal
Reusable

Question 15

Cons of Red rubber tubes

Answer 15

Crack over time - non-repairable
Prone to kinking
Irritant
Not possible to visualise blockages
Low volume high pressure cuff
Can lead to tracheal trauma

Question 16

Pros of Clear PVC tubes

Answer 16

Silicone tubes are repairable
Less prone to kinking
Non-irritant
Allows visualisation of blockages
Usually high volume low pressure cuff
SA that contacts tracheal mucosa is larger
Less risk of tracheal trauma

Question 17

Cons of Clear PVC tubes

Answer 17

Often one use but can be reused?
Less good of a seal - but still good

Question 18

Pros of Armoured Tubes

Answer 18

Resistant to kinking
Useful in animal with flexed neck
Useful in ophthalmic cases

Question 19

Cons of Armoured tubes

Answer 19

Can’t use in MRI - contained metal wire coil
difficult to place without stylet

Question 20

Pros of Cole tubes

Answer 20

Emergency use in paediatric anaesthesia
Useful for exotics

Question 21

Cons of Cole tubes

Answer 21

IPPV can dislodge tube

Question 22

What is an LMA?

Answer 22

Laryngeal Mask Airway
Can be used in combination with ET tube
Doesn’t go into trachea - sits around larynx

Question 23

Pros of LMAs

Answer 23

IPPV possible
Useful in rabbits and cats
Channels to divert regurgitation
Useful for short procedures and bronchoscopy

Question 24

Pros of using Masks

Answer 24

Large range of sizes
Useful for exotics which are difficult to intubate
Good for pre-oxygenation

Question 25

Cons of using masks

Answer 25

Can increase stress in patient - don't use for induction Can cause breath holding Need tight diaphragm seal - don't cover eyes

Question 26

Common complications of Airway management

Answer 26

High pressure/Low volume cuff exerts pressure on a small part of tracheal mucosae (tracheal rupture) Over inflated cuff can cause tracheal strictures or tracheal rupture ○ Subcutaneous emphysema in cats

Question 27

How to prevent tracheal rupture

Answer 27

Don't overinflated cuff - use manometer is possible Use clear PVC tube Don't inflate cuffs in cats when not needed Always disconnect tube from breathing system when repositioning patient

Question 28

How can you assess adequacy of breathing?

Answer 28

Watch chest of patient or reservoir bag For rate and depth of breathing Capnography shows EtCO2 Partial pressure of CO2 exhaled Pulse oximeter shows oxygen saturation in blood

Question 29

What does capnography assess?

Answer 29

MOST IMPORTANT ASSESSMENT OF VENTILATION Non-invasive Alveolar ventilation Shows partial pressure of CO2 exhaled as conc/time Should look square Ideally 35-45mmHg in Dogs (28-45mmHg in cats)

Question 30

What does Pulse Oximetry assess?

Answer 30

SpO2 - Peripheral Arterial Oxygen Saturation Oxygen saturation in blood Ideally >95%

Question 31

How do we know if ventilation is required?

Answer 31

Assess respiratory rate, EtCO2 and SpO2

Question 32

How can you manually ventilate a patient?

Answer 32

1. Close expiratory valve 2. Gently squeeze rebreathing bag whilst watching patients chest rising 3. Stop squeezing when you thing you’ve given enough 4. Open expiratory valve so animal can exhale passively - IMPORTANT Will kill animal if left closed 8-15 breaths/min usually ok (SA) 6-8 for equine (use the CO2 to gauge)

Question 33

What are PEEP valves?

Answer 33

Positive End Expiratory Pressure valves Keep airways open between breaths Uncommon in first opinion Humphrey ADE circle incorporates PEEP valves

Question 34

When are PEEP valves useful?

Answer 34

Paediatric patients - prevents alveoli collapsing Patients which are hypoxaemic on 100% oxygen