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What This Guide Helps With
Troubleshooting unresponsive, inaccurate, unstable, or absent fresh-gas flow caused by supply, control, configuration, circuit, or gas-mixer issues.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended troubleshooting while the Perseus is supporting an active patient.
If fresh-gas delivery becomes unreliable during a case:
- Alert the anesthesia provider immediately.
- Follow the facility’s anesthesia emergency procedure.
- Provide an alternate verified anesthesia machine or manual ventilation equipment with an independent oxygen source.
- Do not allow equipment troubleshooting to delay ventilation, oxygenation, or anesthetic management.
Expected: Patient care is transferred to dependable equipment before Clinical Engineering evaluation begins.
Why it matters: On electronically controlled configurations, ventilation may continue after fresh-gas delivery fails, but the gas mixer may provide no fresh gas. Emergency oxygen delivery or a manual resuscitator may be required.
If patient safety and backup equipment are established, continue troubleshooting off patient.
2. Confirm the Exact Failure Mode
Ask staff what occurred and record the exact alarm or symptom.
Determine whether the complaint involved:
- Fresh-gas controls not responding
- No visible or measured gas flow
- Flow changing without command
- Set flow differing from delivered flow
- One gas unavailable
- Mechanical flow-control valve sticking
- Fresh-gas delivery failure
- Fresh-gas flow inaccurate
- Fresh gas low or leakage
- Flow-control valve still open
Expected: The complaint is separated into a gas-supply, control-input, measurement, leakage, or internal-delivery problem.
3. Identify the Installed Gas-Mixer Configuration
Determine whether the unit uses:
- Electronically controlled gas mixer: Fresh-gas flow, carrier gas, and oxygen concentration are selected through the user interface.
- Mechanically controlled gas mixer: Individual O₂, Air, and optional N₂O flow-control valves are used, with total flow indicated by the flow tube and screen.
Do not apply mechanical-control troubleshooting to an electronic mixer or vice versa.
Expected: Testing is matched to the actual configuration.
4. Verify Medical Gas Supply Connections
Inspect the O₂, Air, and optional N₂O pipeline hoses.
Confirm that:
- Each hose is connected to the correct gas inlet.
- Pipeline connectors are fully inserted into the wall outlets.
- Hoses are not kinked, crushed, damaged, or under tension.
- Gas-supply indicators do not show low or missing pressure.
- Backup cylinders, when installed, contain adequate pressure and are properly connected.
- No nearby anesthesia machine reports the same pipeline problem.
Test the wall outlet and hose with approved equipment when a supply-pressure problem is suspected.
Expected: All required gases show stable, acceptable supply pressure.
If reseating or replacing a defective hose restores normal operation, complete the system test and stop troubleshooting.
5. Check Electrical Power and Device Status
For electronically controlled units:
- Confirm the power cord is connected to a verified receptacle.
- Check the mains-power and battery indicators.
- Inspect for loose connections, damaged cords, tripped receptacles, or abnormal startup messages.
- Confirm the screen and rotary control respond normally.
Do not assume a gas-mixer failure when the device is operating from a depleted battery or has experienced an incomplete startup.
Expected: The device has stable electrical power and normal control-interface operation.
If restoring mains power resolves the control problem, allow the battery to charge and complete the required system test before returning the machine to service.
6. Inspect Fresh-Gas Control Settings
For an electronically controlled mixer:
- Confirm fresh-gas flow is not set to Off.
- Verify the intended carrier gas is selected.
- Check the selected O₂ concentration and total fresh-gas flow.
- Make a controlled setting change and confirm the displayed value responds.
For a mechanically controlled mixer:
- Confirm the required flow-control valves are open.
- Verify the valves rotate smoothly without excessive resistance.
- Observe whether the individual displayed flow and total flow tube respond.
- Confirm unused valves are fully closed.
Do not force a stuck valve or continue using a cracked, loose, or damaged control knob.
Expected: The control input changes smoothly and the indicated fresh-gas flow responds appropriately.
7. Check the Emergency and Auxiliary Oxygen Controls
On electronically controlled configurations, inspect the O₂ switch and flowmeter.
Confirm that:
- The switch has not been unintentionally left in the Add. O₂ emergency-delivery position.
- The auxiliary or emergency O₂ flow-control valve is not unintentionally open.
- The control is returned to its normal operating position.
- Gas flow stops or changes as expected when the emergency system is no longer selected.
Expected: Routine fresh-gas control is not being confused with separate emergency or auxiliary oxygen flow.
If correcting an inadvertently active Add. O₂ control restores normal operation, complete a system test and controlled functional verification before returning the unit to service.
8. Inspect the Breathing Circuit and Breathing Bag
Check for conditions that can resemble a fresh-gas control failure:
- Disconnected or loose breathing hoses
- Major circuit leakage
- Damaged breathing bag
- Breathing bag twisted, blocked, trapped, or incorrectly positioned
- Loose absorber or breathing-system components
- Incorrect external fresh-gas outlet selection
- Open circuit-test ports or accessory connections
Correct visible problems and repeat the system test.
Expected: The breathing system fills normally and does not generate a fresh-gas-low or leakage alarm.
9. Check the Vaporizer Installation
Inspect the installed vaporizer without opening or servicing it.
Confirm that:
- The vaporizer is compatible with the workstation.
- It is fully seated and locked.
- Only the intended vaporizer is active.
- The concentration control moves normally.
- The filler cap or filling system is closed.
- There is no visible damage, leakage, unusual odor, or loose mounting.
If a vaporizer concern exists, remove it from use according to facility procedure and repeat testing with an approved known-good vaporizer or bypass configuration.
Expected: The vaporizer is secure and is not interfering with fresh-gas delivery.
Stop immediately if liquid anesthetic leakage, strong odor, physical damage, or an abnormal control condition is found.
10. Perform the Manufacturer System Test
Place the machine in the required standby or test condition and perform the normal system test using the current Drager instructions for use.
Before starting:
- Connect the required gas supplies.
- Install the breathing circuit and bag correctly.
- Close mechanical flow-control valves when prompted.
- Ensure emergency oxygen controls are in the proper position.
- Follow all on-screen preparation instructions.
Record whether the fresh-gas delivery, gas supply, leakage, and mixer portions pass or fail.
Expected: The complete system test passes without fresh-gas delivery alarms.
A fresh-gas delivery failure may remain active until the system test is successfully completed. A persistent failure after testing requires qualified service evaluation.
11. Verify Fresh-Gas Output in a Controlled Test
Only after the system test passes:
- Connect an approved test lung and gas-analysis equipment as required by hospital procedure.
- Select known fresh-gas settings.
- Confirm that displayed flow responds to setting changes.
- Verify delivered oxygen concentration and total flow against the applicable performance limits.
- For a mechanical mixer, compare the displayed value with the total flow tube.
- Allow readings to stabilize before evaluating accuracy.
Expected: Set flow, displayed flow, and independently measured output agree within the applicable manufacturer specification.
Do not return the device to service based only on screen indications when the original complaint involved inaccurate delivery.
12. Reproduce the Original Complaint
Repeat the operating condition reported by staff without connecting a patient.
Confirm that:
- Controls respond consistently.
- Flow remains stable.
- Gas selection changes correctly.
- No fresh-gas alarms recur.
- No unusual sounds, heat, odors, or delayed responses occur.
- Emergency O₂ and normal fresh-gas delivery remain clearly distinguishable.
Expected: The original problem cannot be reproduced and all required tests pass.
If the issue is resolved, document the cause, test results, and final device status, then stop troubleshooting.
If the Problem Persists
If gas sources, hoses, electrical power, control settings, emergency oxygen controls, breathing-circuit components, vaporizer installation, and system-test preparation have been verified, common external causes have been ruled out.
The likely problem may involve the internal:
- Electronic gas mixer
- Proportional gas-control valve
- Mechanical flow-control assembly
- Gas-supply pressure sensor
- Flow-measurement circuit
- User-interface control
- Internal tubing or pneumatic connection
Do not force controls, enter unauthorized service modes, adjust internal regulators, or disassemble the gas-mixing system.
The anesthesia machine should be:
- Removed from service
- Labeled Out of Service
- Replaced with a verified anesthesia machine
- Sent for qualified bench evaluation or Drager-authorized repair
A recurring fresh-gas delivery failure or failed system test is sufficient reason to keep the machine out of clinical service. Knowing when to stop is proper troubleshooting.
Clinical Use Tip
Never troubleshoot unstable fresh-gas delivery while the machine remains responsible for an active patient. Transfer care first and preserve independent oxygen, ventilation, anesthetic-gas, and physiological monitoring.
Emergency oxygen controls are a temporary clinical contingency, not proof that the normal fresh-gas delivery system is safe for continued use.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Anesthesia staff reported that the Perseus fresh-gas flow setting would not respond and oxygen continued flowing after the electronic flow was reduced."
Cause
What was observed during troubleshooting.
Example:
"The emergency O₂ switch was found in the Add. O₂ position with the separate O₂ flow-control valve open, making the normal electronic fresh-gas controls appear unresponsive."
Resolution
What action was taken.
Example:
"Returned the emergency O₂ controls to the normal position, completed the system test, verified fresh-gas flow and oxygen concentration with approved test equipment, and returned the unit to service."
Helpful Details to Include (If Known)
- Exact alarm text and priority
- Electronic or mechanical gas-mixer configuration
- O₂, Air, and N₂O supply status
- Wall outlets tested
- Pipeline hoses reseated or swapped
- Cylinder pressures
- Emergency O₂ switch position
- Fresh-gas settings when the failure occurred
- Breathing-bag position and condition
- Circuit leakage findings
- Vaporizer model and status
- System-test result
- Set versus measured flow
- Measured oxygen concentration
- Whether the failure was intermittent
- Unusual sounds, heat, or anesthetic odor
- Final device status
Final Thought
Fresh-gas flow problems require immediate attention because displayed ventilation may continue even when normal gas delivery is compromised. Protect the patient first, verify external supplies and controls logically, independently test performance, and escalate persistent mixer or valve failures. Thorough CCR documentation supports safe return to service and effective repair.
That is successful troubleshooting.