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What This Guide Helps With
Troubleshooting failed O2-cell calibration, unavailable oxygen measurement, or inaccurate FiO2 readings caused by setup, gas supply, sampling, sensor, or module issues.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not calibrate, remove, exchange, or test oxygen-measurement components while the Aisys CS2 is supporting an active patient.
If the displayed FiO2 is missing, unstable, or inconsistent with the selected gas mixture:
- Notify the anesthesia provider immediately.
- Confirm oxygen delivery using an approved independent oxygen analyzer.
- Maintain appropriate independent patient and respiratory-gas monitoring.
- Move the patient to another verified anesthesia machine if reliable oxygen delivery or measurement cannot be confirmed.
- Follow the facility’s anesthesia-equipment failure procedure.
Expected outcome: Patient care no longer depends on equipment with questionable oxygen measurement.
Continue troubleshooting only after the machine is removed from active patient use.
2. Confirm Which Oxygen Measurement Is Affected
Determine whether the reported problem involves:
- The circuit O2 cell
- Oxygen measurement from the airway gas module
- A failed Circuit O2 Cell checkout test
- A missing FiO2 value
- A reading that is higher or lower than expected
- A reading that is unstable or slow to respond
- A calibration-required or calibration-failed message
Record the complete displayed alarm, advisory, or checkout message.
Expected outcome: The affected oxygen-measurement path is clearly identified before components are disturbed.
The Aisys CS2 may use a circuit O2 cell and, depending on configuration, an airway module capable of measuring oxygen and other respiratory gases.
3. Verify the Oxygen and Air Supplies
Confirm that:
- The O2 pipeline hose is securely connected.
- Pipeline pressure is available and no supply-pressure alarm is active.
- The air pipeline connection is secure if air is being used.
- Backup cylinders are adequately filled and closed or opened according to the test instructions.
- Gas hoses are not kinked, damaged, crossed, or connected to the wrong outlet.
Low, unstable, or incorrectly connected gas supplies can create an FiO2 value that does not match the selected fresh-gas settings.
Expected outcome: Gas supplies are stable, correctly connected, and free of related alarms.
If correcting the gas supply restores an accurate and stable FiO2 reading, complete checkout and return the machine to service.
4. Allow the Machine to Complete Startup
Perform a normal shutdown and restart while the machine is disconnected from patient use.
Allow the Aisys CS2 to:
- Complete its startup sequence.
- Recognize installed monitoring components.
- Display any active system messages.
- Stabilize before evaluating the oxygen reading.
Do not repeatedly cycle power if the same error immediately returns.
Expected outcome: A temporary startup or communication problem clears and the oxygen-measurement components are recognized.
5. Inspect the Circuit O2 Cell Externally
If the machine is equipped with a circuit O2 cell:
- Confirm the cell is present and fully seated.
- Inspect the accessible connector and cable for looseness, contamination, bent contacts, cuts, or strain.
- Check that the cell opening is unobstructed.
- Look for moisture, absorbent dust, cleaning residue, or physical damage.
- Confirm the cell has not been installed incorrectly after cleaning or breathing-system service.
Do not open the sensor body or attempt internal repair.
Expected outcome: The O2 cell is correctly installed, clean, dry, and externally undamaged.
If reseating a loose connection restores normal operation, run the required checkout before returning the machine to service.
6. Inspect the Breathing Circuit and Gas Path
Confirm that:
- The breathing circuit is assembled correctly.
- Inspiratory and expiratory limbs are properly connected.
- The absorber canister and breathing-system components are fully seated.
- No circuit component is retaining excessive moisture.
- Filters, adapters, test lungs, and accessories are not blocking gas flow.
- No supplemental gas source is altering the expected oxygen concentration.
Expected outcome: The oxygen sensor is exposed to a stable and representative gas mixture.
7. Inspect the Airway Gas Module and Sampling Components
If FiO2 is obtained through the airway gas module:
- Confirm the module is fully inserted and recognized.
- Inspect the sampling line for disconnection, kinks, blockage, cracks, or fluid contamination.
- Check the water trap and replace it with an approved compatible component if saturated, damaged, or overdue.
- Confirm all sample-line fittings are tight.
- Allow adequate warm-up and stabilization time after installing or exchanging the module.
- Compare the oxygen value with an approved external analyzer.
The airway module measures and monitors gases delivered to and exhaled by the patient; sampling problems can therefore affect the displayed oxygen value.
Expected outcome: Sampling is unobstructed, the module is recognized, and its oxygen value is stable.
8. Run the Circuit O2 Cell Test
From the Checkout menu, perform the appropriate Circuit O2 Cell test by following the on-screen instructions.
During the room-air portion:
- Make sure the circuit is exposed to room air as instructed.
- Wait for the displayed oxygen value to stabilize near 21%.
- Do not select Done immediately when 21% first appears.
- Complete the test only after the reading has stabilized.
GE’s Aisys CS2 training material specifically instructs allowing the reading to stabilize before completing the Circuit O2 Cell test.
Expected outcome: The Circuit O2 Cell test completes successfully.
If the test passes and the oxygen reading remains accurate during functional testing, stop troubleshooting.
9. Perform the Approved O2-Cell Calibration
If calibration is requested or the Circuit O2 Cell test does not pass:
- Use only the calibration process available through the machine’s approved checkout or service interface.
- Follow the on-screen prompts exactly.
- Ensure the required reference gas condition is stable.
- Do not breathe into the circuit or allow supplemental oxygen to contaminate a room-air calibration.
- Allow the displayed value to stabilize before accepting the calibration.
- Do not perform undocumented calibration adjustments.
Expected outcome: Calibration completes without an error and the displayed oxygen value agrees with the reference condition.
The Aisys CS2 checkout documentation directs calibration of the O2 cell when necessary following evaluation of the stabilized reading.
10. Compare the Reading With an Independent Analyzer
Using an approved, calibrated oxygen analyzer:
- Check the circuit at room-air concentration when appropriate.
- Test one or more controlled oxygen concentrations.
- Allow both devices to stabilize.
- Compare the Aisys CS2 reading with the independent analyzer.
- Observe whether the displayed value responds appropriately when the oxygen setting changes.
Do not rely solely on the selected fresh-gas setting as proof of delivered FiO2.
Expected outcome: The displayed oxygen concentration is stable, responsive, and within the facility’s approved performance tolerance.
11. Substitute Approved External Components When Available
If permitted by facility policy and manufacturer guidance:
- Try a known-good compatible circuit O2 cell.
- Try an approved sampling line and water trap.
- Try a known-good compatible airway module.
- Exchange one component at a time.
- Repeat calibration and checkout after each exchange.
Do not use unverified sensors or modules from equipment with unresolved problems.
Expected outcome: The faulty external sensor, module, or sampling component is isolated.
If replacement resolves the issue, complete the full checkout and document the component exchanged.
12. Complete a Full Checkout
After correction:
- Run the Full Test or all required individual checkout tests.
- Verify the Circuit O2 Cell test passes when the cell is installed.
- Confirm the airway module is recognized.
- Compare FiO2 with an independent analyzer.
- Verify alarms, ventilation, gas delivery, and monitoring.
- Review the checkout log for unresolved failures.
GE identifies the Circuit O2 Cell test as part of the Aisys CS2 checkout when that cell is present.
Expected outcome: All required tests pass and oxygen measurement remains accurate and stable.
If the Problem Persists
If calibration repeatedly fails, FiO2 remains inaccurate, or the oxygen reading is unavailable after external components, gas supplies, sampling parts, connections, and checkout conditions have been verified, common external causes have been ruled out.
The problem may involve an internally failed sensor circuit, module interface, wiring connection, signal-processing component, or gas-measurement assembly.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for authorized repair or controlled bench evaluation
- Evaluated using the current GE Healthcare technical reference documentation and required test equipment
Do not proceed with undocumented internal adjustments or board-level repairs. Knowing when to stop and escalate is proper troubleshooting.
Clinical Use Tip
Never troubleshoot questionable FiO2 measurement on an active patient. Establish independent oxygen monitoring or move the patient to another verified anesthesia machine before testing, calibration, or component exchange.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Anesthesia staff reported that the Aisys CS2 displayed an unstable FiO2 value and would not complete the Circuit O2 Cell test."
Cause
What was observed during troubleshooting.
Example:
"Inspection found moisture contamination around the circuit O2 cell connection, preventing the reading from stabilizing during checkout."
Resolution
What action was taken.
Example:
"Removed the machine from service, dried and reseated the approved O2 cell, completed calibration, verified readings with an independent oxygen analyzer, and passed the full checkout."
Helpful Details to Include (If Known)
- Complete alarm or checkout message
- Circuit O2 cell or airway-module measurement affected
- O2 and air pipeline status
- Cylinder pressures
- Circuit O2 cell inspected or exchanged
- Airway module recognition status
- Sampling line and water-trap condition
- Room-air reading
- Independent analyzer readings
- Calibration result
- Circuit O2 Cell test result
- Full checkout result
- Final device status
Final Thought
Accurate oxygen measurement is essential to safe anesthesia delivery. Begin with patient protection, verify gas supplies and external components, use stable calibration conditions, confirm performance independently, and escalate when the measurement cannot be trusted. Clear CCR documentation preserves both patient safety and repair history.
That is successful troubleshooting.