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What This Guide Helps With
Troubleshooting unavailable, unstable, or incorrect fresh-gas flow caused by gas supplies, flow controls, settings, startup conditions, or external connections.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended fresh-gas flow troubleshooting while the WATO EX Series anesthesia machine is supporting an active patient.
If fresh-gas delivery becomes unavailable, unstable, or inconsistent during clinical use:
- Notify the anesthesia provider immediately.
- Confirm ventilation, oxygen concentration, airway pressure, and respiratory-gas measurements using approved independent monitoring.
- Use another verified anesthesia machine or approved backup ventilation method when reliable gas delivery cannot be confirmed.
- Follow the facility’s anesthesia-equipment failure procedure.
Expected outcome: Patient care no longer depends on equipment with uncertain fresh-gas delivery.
Continue troubleshooting only after the machine has been safely removed from active patient use.
2. Confirm the Exact Failure Condition
Record the complete displayed alarm, advisory, or startup-test message.
Determine whether:
- One gas flow cannot be adjusted.
- Total fresh-gas flow remains at zero.
- Flow is lower or higher than the selected value.
- Flow settings change but the displayed flow does not respond.
- Flow is unstable or fluctuating.
- The problem began after startup, a cylinder change, pipeline reconnection, or vaporizer installation.
- A backup flow-control message or mode is displayed on equipped models.
Expected outcome: The affected gas, control, and operating condition are clearly identified.
If the reported condition cannot be reproduced, review alarm logs and obtain details from the clinical user before returning the unit to service.
3. Verify Medical Gas Availability
Confirm that the required pipeline hoses are:
- Connected to the correct wall outlets.
- Fully seated at both ends.
- Free from visible damage, crushing, or severe bends.
- Connected to the correct gas inlets on the machine.
Check the machine’s displayed supply-pressure indicators for oxygen, air, and nitrous oxide, as equipped.
If cylinders are installed:
- Confirm the correct cylinder is attached.
- Verify that the cylinder contains adequate pressure.
- Open the cylinder valve slowly.
- Check for an expected pressure indication.
- Close the cylinder after testing unless facility procedure requires it to remain available.
The WATO EX Series requires an adequate drive-gas and medical-gas supply for normal operation; published WATO EX-65 specifications list a ventilator driving-pressure range of 280–600 kPa.
Expected outcome: Required gases show normal supply pressure without supply alarms.
If the issue is corrected after restoring the gas supply, complete the operational checkout and stop troubleshooting.
4. Isolate the Pipeline Supply
Connect the machine to a different verified wall outlet using an approved gas hose, when available.
Alternatively, test temporarily from a verified backup cylinder in accordance with facility policy.
If flow operates normally from the alternate source, investigate the original pipeline outlet, hose, connector, or facility gas supply.
If the failure remains with both pipeline and cylinder sources, continue troubleshooting the anesthesia machine.
Expected outcome: The facility supply is either identified as the cause or ruled out.
5. Inspect the Flow-Control Interface
Depending on the WATO EX model, fresh-gas flow may be adjusted using mechanical flow controls or an electronic digital gas mixer. Mindray describes the WATO EX-65 Pro as using a digital gas mixer with total-flow and direct-flow control modes.
Check that:
- Mechanical flow-control knobs rotate normally without binding.
- Electronic controls respond to touch or rotary-knob input.
- The selected carrier gas is appropriate.
- The machine is not in Standby or another condition that intentionally suspends gas delivery.
- The displayed flow-control mode matches the operator’s intended method.
- No control is physically obstructed or damaged.
Do not force a stiff flow-control knob or repeatedly operate an unresponsive electronic control.
Expected outcome: Controls move normally and corresponding settings change on the display.
If a damaged, loose, or binding control is found, remove the device from service for repair.
6. Verify Fresh-Gas Settings
Confirm that the selected settings are clinically reasonable and not unintentionally set to minimum or zero flow.
Check:
- Total fresh-gas flow.
- Individual oxygen, air, and nitrous oxide settings, as equipped.
- Selected oxygen concentration.
- Carrier-gas selection.
- Low-flow optimizer recommendations versus actual control settings on equipped models.
The optimizer is guidance for fresh-gas efficiency; it does not by itself prove that the gas-delivery system is functioning correctly. Mindray documentation describes the optimizer as indicating whether fresh-gas flow is insufficient, appropriate, or excessive.
Expected outcome: Selected flow and gas-mixture values are appropriate and accepted by the machine.
If correcting an unintended setting restores normal delivery, perform a complete checkout and stop troubleshooting.
7. Check for Hypoxic-Guard or Gas-Supply Limitations
Verify whether the machine is intentionally limiting nitrous oxide or total gas flow because of:
- Insufficient oxygen supply.
- An oxygen supply-pressure alarm.
- An oxygen concentration setting that conflicts with the requested gas mixture.
- An active gas-ratio protection function.
- An unavailable carrier gas.
Restore a verified oxygen supply before evaluating other gas-flow controls.
Do not attempt to bypass oxygen-ratio protection or other safety functions.
Expected outcome: Gas-ratio safety functions permit the selected mixture after adequate oxygen supply is restored.
8. Inspect the Common Gas Path and External Connections
Check externally accessible components for incorrect setup or obstruction:
- Common gas outlet connection.
- Auxiliary common gas outlet, if equipped.
- Fresh-gas hose or breathing-system connection.
- Breathing-system mounting and locking position.
- Vaporizer seating and interlock position.
- External non-rebreathing circuit connections.
- Kinked, collapsed, or incorrectly routed tubing.
Confirm that gas is being directed to the intended outlet and not unintentionally diverted to an auxiliary outlet.
Expected outcome: The fresh-gas pathway is correctly assembled, unobstructed, and directed to the intended breathing system.
If correcting a connection restores proper flow, complete the machine checkout and stop troubleshooting.
9. Inspect the Vaporizer Installation
Confirm that each vaporizer is:
- Approved for the machine.
- Fully seated on its mounting system.
- Locked into position.
- Not positioned between settings.
- Free from obvious physical damage or leakage.
- Properly interlocked so that only one vaporizer can be activated.
Turn all vaporizers off and determine whether normal carrier-gas flow can be established.
Do not remove or install a vaporizer while gas is actively flowing unless permitted by the manufacturer’s instructions.
Expected outcome: Normal fresh-gas flow is available with vaporizers off and correctly mounted.
If flow failure occurs only when a specific vaporizer is activated, remove that vaporizer from use and evaluate it separately.
10. Perform a Controlled Restart
After recording all displayed messages:
- Place the machine in Standby.
- Turn all vaporizers off.
- Confirm that no patient is connected.
- Shut down the system normally.
- Verify the power cord and medical-gas connections.
- Restart the machine.
- Allow the complete startup sequence to finish.
Do not repeatedly power-cycle the machine to clear a persistent fault.
Expected outcome: The system completes startup without a fresh-gas control or internal communication fault.
If normal operation returns, continue with a complete pre-use checkout before considering the device ready for service.
11. Run the Approved System Checkout
Perform the operator-level pre-use checkout or leak/compliance test specified for the exact WATO EX model.
Before testing:
- Set the Auto/Manual control as directed.
- Zero the fresh-gas flow controls when prompted.
- Ensure the breathing circuit and test lung are correctly installed.
- Follow all on-screen instructions.
Mindray service documentation indicates that detected fresh-gas flow can prevent completion of certain leak tests and may prompt the operator to zero all flowmeters.
Expected outcome: The machine passes its startup, leak, compliance, and gas-delivery checks without recurring flow-control messages.
Do not return the device to clinical use if the checkout fails or must be overridden.
12. Verify Delivered Flow With Approved Test Equipment
Using an anesthesia-machine analyzer or calibrated flow-measurement device:
- Measure total fresh-gas flow at the appropriate outlet.
- Compare measured flow with the selected or displayed value.
- Test several clinically relevant flow settings.
- Verify oxygen concentration with an independent oxygen analyzer.
- Confirm stable output without unexpected fluctuation.
Use the acceptance limits and test method specified in the applicable Mindray service documentation and facility procedure.
Expected outcome: Measured flow and oxygen concentration remain stable and within the manufacturer’s permitted tolerances.
If displayed settings do not agree with independently measured output, remove the machine from service.
If the Problem Persists
If verified gas supplies, hoses, settings, controls, vaporizers, external connections, and the breathing-system setup have been ruled out, the failure is likely internal.
Possible internal causes include:
- Electronic gas-mixer failure.
- Flow-control valve malfunction.
- Flow-sensor or measurement failure.
- Pneumatic manifold leakage or restriction.
- Control-board or internal communication failure.
- Backup flow-control system fault on equipped models.
- Damaged mechanical needle-valve or flowmeter components.
The anesthesia machine should be:
- Removed from service.
- Labeled Out of Service.
- Sent for authorized repair or bench evaluation.
- Tested with calibrated anesthesia-machine analysis equipment before being returned to clinical use.
Do not perform internal pneumatic adjustments, valve replacement, calibration, or board-level repair without the appropriate Mindray service documentation, training, and test equipment.
Knowing when to stop external troubleshooting is proper troubleshooting.
Clinical Use Tip
Never troubleshoot uncertain fresh-gas delivery on an active patient. Transfer the patient to another verified anesthesia machine before changing gas supplies, vaporizers, flow controls, or system configuration.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Anesthesia staff reported that the Mindray WATO EX Series machine would not increase total fresh-gas flow above zero."
Cause
What was observed during troubleshooting.
Example:
"Oxygen pipeline pressure was absent because the oxygen hose was not fully seated in the wall outlet, causing the machine to restrict gas delivery."
Resolution
What action was taken.
Example:
"Reseated the oxygen pipeline hose, confirmed normal supply pressure, verified fresh-gas flow and oxygen concentration with an analyzer, completed the system checkout, and returned the machine to service."
Helpful Details to Include (If Known)
- Complete alarm or advisory text
- Affected gas or flow-control channel
- Pipeline pressures verified
- Backup cylinders tested
- Gas hoses inspected or exchanged
- Flow-control mode selected
- Vaporizer status
- Common gas outlet or ACGO position
- Displayed flow versus measured flow
- Measured oxygen concentration
- Startup and leak-test results
- Indicator lights or supply-pressure symbols
- Unusual sounds, heat, odor, or gas leakage
- Final device status
Final Thought
Fresh-gas flow failures can directly affect oxygen and anesthetic delivery. Protect the patient first, verify external supplies and configuration logically, measure actual output independently, and escalate persistent faults with complete CCR documentation.
That is successful troubleshooting.