Airway Management Flashcards
Why is airway management important?
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
IPPV
Intermittent Positive Pressure Ventilation
Hypoxia
Low oxygen concentration in tissues
Hypercapnia
High CO2 concentration in blood
Hypoxaemia
Low oxygen concentration in blood
What are the methods of providing oxygen?
Oxygen cylinders (size E or J)
Oxygen Concentrators
Which size of oxygen cylinder is bigger?
J - kept outside
E is smaller
Pros of Oxygen concentrators
Extracts oxygen from environment - endless supply
More portable than cylinders
Cons of oxygen concentrators
Need electrical power supply - will need a back up if power fails
90-95% pure oxygen not 100%
How do you measure ET tube against patient
From nares to point of shoulder
Doesn’t need to go as deep in cats (just past larynx)
Parts of an ET tube
Machine end - adapter
Radiopaque marker line
Murphy eye - safety feature
Cuff
pilot line/balloon
Types of ET tube
Red rubber
Clear PVC
Armoured Tubes
Cole Tubes
What is important about intubating cats?
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
Pros of Red Rubber Tubes
Good seal
Reusable
Cons of Red rubber tubes
Crack over time - non-repairable
Prone to kinking
Irritant
Not possible to visualise blockages
Low volume high pressure cuff
Can lead to tracheal trauma
Pros of Clear PVC tubes
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
Cons of Clear PVC tubes
Often one use but can be reused?
Less good of a seal - but still good
Pros of Armoured Tubes
Resistant to kinking
Useful in animal with flexed neck
Useful in ophthalmic cases
Cons of Armoured tubes
Can’t use in MRI - contained metal wire coil
difficult to place without stylet
Pros of Cole tubes
Emergency use in paediatric anaesthesia
Useful for exotics
Cons of Cole tubes
IPPV can dislodge tube
What is an LMA?
Laryngeal Mask Airway
Can be used in combination with ET tube
Doesn’t go into trachea - sits around larynx
Pros of LMAs
IPPV possible
Useful in rabbits and cats
Channels to divert regurgitation
Useful for short procedures and bronchoscopy
Pros of using Masks
Large range of sizes
Useful for exotics which are difficult to intubate
Good for pre-oxygenation
Cons of using masks
Can increase stress in patient - don’t use for induction
Can cause breath holding
Need tight diaphragm seal - don’t cover eyes
Common complications of Airway management
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
How to prevent tracheal rupture
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
How can you assess adequacy of breathing?
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
What does capnography assess?
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)
What does Pulse Oximetry assess?
SpO2 - Peripheral Arterial Oxygen Saturation
Oxygen saturation in blood
Ideally >95%
How do we know if ventilation is required?
Assess respiratory rate, EtCO2 and SpO2
How can you manually ventilate a patient?
- Close expiratory valve
- Gently squeeze rebreathing bag whilst watching patients chest rising
- Stop squeezing when you thing you’ve given enough
- 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)
What are PEEP valves?
Positive End Expiratory Pressure valves
Keep airways open between breaths
Uncommon in first opinion
Humphrey ADE circle incorporates PEEP valves
When are PEEP valves useful?
Paediatric patients - prevents alveoli collapsing
Patients which are hypoxaemic on 100% oxygen
