Anaesthesia Machine Check Protocol

Why It Matters

A. Start-of-Day (Full) Check

1. Preparation

• Ensure master switch is off, pipelines disconnected, all cylinders closed, and any residual gases exhausted (pressure gauges read zero).
• Confirm backup equipment is present and functional: self-inflating bag (Ambu), auxiliary O2 cylinder, functioning suction.
• Confirm the machine is connected to mains (AC) power. Battery backup should have at least 30 minutes of charge.

2. Gas Supply - High Pressure System (Cylinders)

3. Gas Supply - Pipeline System (Intermediate Pressure)

• Reconnect pipeline supplies.
• Check all pipeline pressure gauges read 400-500 kPa (approximately 58-73 psi or ≥50 psig).
• Confirm O2 pipeline connects to the O2 inlet only (anti-cross-connection through Schrader probes or NIST fittings - these are non-interchangeable by design, but visual confirmation is still required).
• Perform pipeline tug test to confirm secure connection.

4. Low Pressure System (Flowmeters and Vaporizers)

• Turn master switch on.
• If the machine has minimum mandatory flows, confirm O2 flowmeter registers 50-200 mL/min with the O2 flow control knob turned off.
• Test all flowmeters: look for bobbin/ball damage, sticky floats, and correct full range of flow.
• Check vaporizers are adequately filled; confirm filler ports are tightly closed.
• Check vaporizer interlock (only one vaporizer can be on at a time).
• Perform low-pressure system leak test (negative pressure / syringe test):
  • With the vaporizer off and common gas outlet occluded, compress a syringe attached to the outlet - no refill should occur (leak <100 mL/min).
  • Repeat for each vaporizer individually (turn each on during the test, then off).
  • Leaks as low as 100 mL/min can critically reduce volatile agent concentration and risk intraoperative awareness.

5. Oxygen Monitoring and Fail-Safe

• Calibrate the O2 analyser (or verify calibration):
  • Reads ~21% in room air.
  • Reads >95% in 100% O2 flow.
• Check the low O2 alarm activates at the set threshold (typically ≤25-30%).
• Confirm the oxygen failure alarm (Ritchie whistle / audible alarm) sounds when O2 supply pressure drops.
• Confirm the hypoxic guard (proportioning system) prevents delivery of <21% O2.

6. Breathing System (Circle System or T-piece)

• Inspect the circuit for correct configuration and assembly: no missing components, all connections tight.
• Check CO2 absorber (soda lime/Amsorb):
  • Confirm it is not exhausted (colour change indicator, adequate volume).
  • No dry or overheated absorbent.
• Perform pressure/leak test of the breathing circuit:
  1. Occlude the patient port.
  2. Fill the system to 30 cmH2O with the O2 flush.
  3. Close the APL (pop-off) valve.
  4. No pressure drop over 10 seconds = no significant leak.
• Check APL (adjustable pressure-limiting) valve opens and closes correctly.
• Check unidirectional valves (inspiratory and expiratory) are present and moving freely.
• Confirm gas flows correctly through both inspiratory and expiratory limbs.
• Check filters and HME connectors are fitted correctly.

7. Ventilator

• Configure ventilator for intended use (volume control, pressure control as needed).
• Ensure ventilator tubing is securely attached.
• Set initial controls and confirm adequate inspiratory pressure is generated.
• Confirm alarms are active and correctly set: high pressure, low pressure (disconnect alarm), minute volume.
• Check pressure relief valve functions at the set pressure.
• Confirm bellows or piston moves correctly and returns to baseline.

8. Scavenging System

• Confirm the anaesthetic gas scavenging system (AGSS) is switched on and functioning.
• Ensure tubing is attached to the correct exhaust port of the breathing system, ventilator, or workstation.
• Check for no obstruction in the scavenging pathway (a blocked scavenging system can cause dangerously raised airway pressures).

9. Monitoring Equipment

10. Suction

• Confirm suction is available, tubing is connected, and generates adequate negative pressure.
• Yankauer sucker should be at hand.

11. Ancillary Equipment and Drugs

• Check airway equipment for the planned case: laryngoscope (blade light working, spare batteries), ETT (cuff inflates/deflates), LMA, bougie, CICO (can't intubate, can't oxygenate) rescue equipment.
• Confirm drugs drawn up or available: induction agent, muscle relaxant, reversal agents, vasopressors, analgesics.
• Verify sufficient CO2 absorbent and volatile agent in the vaporizer.

12. Documentation

• Record completion of the check with the date, time, and name of the checking anaesthetist on the machine log.
• This is a medicolegal requirement.

B. Between-Case Check (Start of Each Patient)

C. During a Long Case

• Periodically check for exhaustion of volatile agent in the vaporizer.
• If an O2 cylinder was used during the case, confirm it is at least half full before the next patient or replace it.
• On handover between anaesthetists mid-case, formal machine check status must be communicated.

D. After a Critical Incident

Key Reference Values Summary

Sources

• AAGBI Safety Guideline - Checking Anaesthetic Equipment 2012 (Hartle et al., Anaesthesia 2012) - The primary UK/RCOA standard
• ASA/APSF 2008 Pre-Anaesthesia Checkout Recommendations - The primary US standard (15 daily items, 8 per-case items)
• Anaesthesia Machine: Checklist, Hazards, Scavenging - PMC (Indian J Anaesth, 2013)

Note: Always supplement this protocol with your institution's specific checklist and the manufacturer's instructions for your machine model, as automated self-checks vary significantly between systems and do not replace manual verification of all items.