Anaesthetic Machine Check

An anaesthesia delivery system includes any equipment that can deliver gases, vapours, local anaesthetic or intravenous anaesthetic agents.

Process

There are three levels of machine check:

Level One Check
Detailed check performed by trained service personenel of all systems prior to being used.
Level Two Check
Check performed at that start of each anaesthetic list.
Level Three Check
Check performed prior to commencing anaesthesia for each patient.

Level Two Check

Check gas pressures
- Supply line pressures
- Reserve O₂ cylinder pressure
  - Adequate pressure
    >10,000 kPa.
  - Can be turned on and off
    Leave off after check so that there is no slow leak.
  - Not leaking from seal
Check gas flows
- Check that each gas flow is measured correctly on each rotameter
- Verify that the anti-hypoxic systems are working correctly
  - FiO₂ should not be able to be reduced to <0.21
Check scavenging
Connected and flow is adequate.
Check vapourisers
- Filled with liquid anaesthetic
- Seated and detected appropriately
Check CO₂
- Check soda lime
- Check ETCO₂ working
Check for circuit leak
- Leak should be ≤300ml/min for a circuit pressure >30cm H₂O
- Usually automated in modern machines
Manual circuit check
Attach a circuit bag to the patient y-piece and test:
- Circuit compliance
- Circuit resistance
- Valve movement
- APL valve function
  Compress both circuit bag and breathing bag.
Verify BVM is present
Check emergency drugs

Level Three Check

The level three check involves checking any piece of equipment that has been changed.

Intravenous Anaesthesia Delivery Systems

Device is powered and functions correctly
Drug is correctly labelled and loaded
Correct programming of:
- Syringe type and volume
- Drug used and concentration
- Flow rate and units
- Alarm parameters
Antireflux valve placed
Secure connections
No leakage

Principles

Facility must designate an individual responsible for servicing and maintenance
Anaesthesia delivery systems should be serviced regularly
Alarms and monitoring should comply with ANZCA standards
Secondary means of oxygenation and positive pressure ventilation should be available

Machine Safety

Additionally, anaesthetic machines:

Should be assessed yearly by a specialist anaesthetist for:
- Safety
- Reliability
- Functionality
That do not comply with the following safety requirements to be removed from clinical use, or be upgraded to do so
- Gas supply
  - Gas cylinder connections must be pin indexed
  - Reserve oxygen suppply must be attached and easily activatable
  - Non-interchangeable gas hose connectors
  - Supply gas pressure display visible
  - Oxygen failure warning device present
    - Generates alarm
    - Cut off supply of gases other than air and oxygen to common gas outlet
  - Oxygen must be the last gas to enter the backbar
  - If flowmeters are used:
    - Only one gas flow control knob for each gas
    - Oxygen knob should differ from other knobs so it can be identified by touch
      Generally fluted.
    - Oxygen flow knob must be left-most
  - Incapable of delivering a hypoxic mixture
    i.e. FiO₂ ⩽21%.
- Vaporisers
  - Interlock must prevent more than one vaporiser being used
  - Gas concentraiton must ↑ when dial rotated anti-clockwise
- Fresh gas outlet
  Must be:
  - 22mm outer diameter and 15mm internal diameter
  - Visible
  - Connected in such a way to prevent accidental disconnection
- High-presure release valve present in the circuit
- Scavenging must be of a different diameter to other connections
- All alarms must activate when the associated feature of the machine isenabled
- Emergency oxygen flush must be protected from accidental activation
- On/off switch must be protected from unintended activation
  Turning off during normal operation requires a confirmatory step.