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What This Guide Helps With
This guide addresses situations where the Mindray WATO EX Series anesthesia machine:
- Shows alarms related to gas or anesthetic agent delivery (e.g., low flow, agent not detected, unexpected concentrations)
- Fails to deliver set gas mixtures or volatile agents accurately
- Displays inconsistent readings on the agent monitor
The focus is on external, easily verifiable causes first, before assuming internal component failure.
Step-by-Step Troubleshooting
Verify Power and Startup Sequence
- Ensure the machine is plugged into a properly grounded outlet and powered on.
- Observe the startup self-test; note any errors related to gas delivery.
- Why: Some delivery errors occur if the machine did not complete self-tests correctly.
Check Gas Supply Lines
- Inspect O₂, N₂O, and Air pipelines for pressure and flow.
- Confirm cylinders are open, regulators are set correctly, and pipeline pressures are within normal range.
- Why: Low or no supply pressure can trigger gas delivery alarms.
Inspect Flowmeters and Vaporizers
- Ensure vaporizers are seated properly and filled with the correct agent.
- Check for leaks at vaporizer mounts or interlocks.
- Verify flowmeter readings respond correctly when adjusting flows.
- Why: Misaligned vaporizers or empty reservoirs can prevent accurate agent delivery.
Examine Breathing Circuit and Connectors
- Look for disconnections, leaks, or kinks in the circuit tubing.
- Confirm that the CO₂ absorber is installed correctly and not bypassed.
- Why: Circuit leaks can mimic gas delivery errors.
Review Alarm and Monitoring Settings
- Confirm agent and gas concentration alarms are set within normal limits.
- Reset alarms and observe if error persists.
- Why: Incorrect alarm limits can give false error readings.
Test With a Simulated Lung (if available)
- Run a test ventilation with a test lung using O₂ and air only.
- Observe delivered volumes and agent readings without a patient.
- Why: Helps determine if error is patient-specific or machine-related.
If the Problem Persists
All external checks (power, supply, circuit, vaporizers) have been verified.
Device may have internal issues such as flow sensor failure, electronic controller malfunction, or vaporizer interface fault.
- Remove the machine from service.
- Label it Out of Service.
- Send to the Biomedical Engineering bench or authorized repair center.
Knowing when to stop is proper troubleshooting.
Clinical Use Tip
Never attempt gas delivery troubleshooting on a patient—always switch to a backup machine first.
Ensure oxygen supply is available and the patient is safely ventilated before any troubleshooting.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
“Machine is displaying low agent delivery alarm and O₂/N₂O concentrations are inconsistent.”
Cause
What was observed during troubleshooting.
Example:
“Observed vaporizer not fully seated; gas supply pressures within normal range; flowmeters respond properly when tested.”
Resolution
What action was taken.
Example:
“Re-seated vaporizer and verified agent fill. Ran test lung simulation. Error resolved. Machine returned to service.”
Helpful Details to Include
- Cylinder or pipeline pressures
- Vaporizer type and fill level
- Flowmeter readings
- Alarm codes displayed
- Circuit check results
- Test lung simulation results
Final Thought
Systematic, logic-based troubleshooting protects patient safety, minimizes unnecessary downtime, and ensures proper escalation when internal issues exist. Detailed documentation allows future reference and accountability.
That is successful troubleshooting.