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What This Guide Helps With
Troubleshooting failed O₂ cell calibration, oxygen-concentration alarms, or inaccurate FiO₂ caused by gas supply, connections, sensor condition, settings, or calibration problems.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not troubleshoot suspected oxygen-measurement or delivery problems while the Servo-i is actively supporting a patient.
- Notify respiratory therapy and the clinical team.
- Transfer the patient to another verified ventilator or approved ventilation method.
- Confirm adequate ventilation and oxygenation using independent clinical monitoring.
- Do not rely on the displayed FiO₂ when its accuracy is in question.
Expected outcome: The patient is safely supported without relying on the affected ventilator.
Continue Clinical Engineering troubleshooting only after the Servo-i has been removed from patient use.
2. Confirm the Exact Failure
Review the reported symptom and determine whether the Servo-i:
- Fails the O₂ cell portion of the pre-use check
- Displays an O₂ cell or oxygen-concentration alarm
- Shows FiO₂ that does not match the selected setting
- Displays an unstable or slowly drifting oxygen value
- Passes at low FiO₂ but becomes inaccurate at higher settings
- Recently had its O₂ cell, gas hose, or inspiratory components replaced
Record the complete alarm wording and whether the problem is constant or intermittent.
Expected outcome: The failure is clearly identified as a calibration, measurement, or oxygen-delivery problem.
3. Inspect the Oxygen Supply
Verify that the oxygen hose is:
- Connected securely to the Servo-i
- Connected to the correct facility oxygen outlet
- Free from kinks, crushing, contamination, or visible damage
- Equipped with the correct fittings
- Fully seated at both ends
Confirm that the oxygen source is available and within the facility’s acceptable supply-pressure range. Test the outlet with an approved gas-pressure device or move the ventilator to a known-good oxygen outlet when appropriate.
Expected outcome: The ventilator receives a stable oxygen supply without leakage or restriction.
If the calibration succeeds after correcting the supply, document the finding and stop.
4. Verify the Air Supply
Confirm that the compressed-air hose is securely connected and that the air source is available and stable.
The Servo-i blends air and oxygen to produce the selected FiO₂. A missing, restricted, or incorrectly connected gas source may cause inaccurate oxygen delivery or prevent successful testing.
- Inspect the air hose and fittings.
- Test the wall outlet when indicated.
- Compare operation using known-good air and oxygen sources.
- Verify that the hoses have not been accidentally reversed.
Expected outcome: Both gas sources are properly connected and available.
5. Allow the Ventilator to Stabilize
If the Servo-i was recently moved from a cold or hot environment, allow it to reach room temperature before repeating calibration.
Rapid temperature changes, condensation, or insufficient stabilization time may affect sensor performance.
- Place the ventilator in a clean, dry environment.
- Confirm that no condensation is visible around gas connections.
- Power the unit normally.
- Allow sufficient stabilization before rerunning the pre-use check.
Expected outcome: Environmental conditions are stable and suitable for calibration.
6. Inspect the O₂ Cell and Accessible Connections
With the ventilator powered off and removed from service, inspect the externally accessible O₂ cell installation according to facility-approved procedures.
Check for:
- A loose or incorrectly seated O₂ cell
- A disconnected or damaged sensor cable
- Bent, recessed, contaminated, or corroded contacts
- Moisture around the cell or inspiratory gas path
- A missing seal or visibly damaged mounting area
- An expired installation or replacement date
Do not open protected assemblies or proceed with internal disassembly unless authorized and trained under the manufacturer’s service program.
Expected outcome: The O₂ cell and its accessible connections are clean, dry, undamaged, and properly seated.
If reseating an accessible connection resolves the problem, repeat the complete pre-use check before returning the ventilator to service.
7. Check the O₂ Cell’s Age and Service History
Review the equipment history for:
- O₂ cell installation date
- Previous calibration failures
- Recurring oxygen-concentration alarms
- Recent oxygen-cell replacement
- Extended storage without operation
- Exposure to excessive heat, humidity, or oxygen concentration
Electrochemical oxygen cells are consumable components whose output decreases with age and use. A cell may become slow, unstable, or unable to reach the required calibration range before it fails completely.
Expected outcome: The O₂ cell is within the facility’s approved replacement interval and has no history suggesting deterioration.
8. Replace a Suspect O₂ Cell When Authorized
If external gas supplies and connections are verified but calibration continues to fail, replace the O₂ cell with the correct approved replacement part when permitted by facility policy and technician authorization.
- Verify the replacement part is correct for the Servo-i configuration.
- Confirm packaging integrity and expiration information.
- Install the cell according to approved service instructions.
- Allow the new cell to stabilize when required.
- Do not use unapproved or incompatible oxygen sensors.
Expected outcome: The replacement cell is recognized and produces stable oxygen measurements.
9. Run the Complete Pre-Use Check
Connect the Servo-i to known-good air and oxygen sources and perform the complete pre-use check, following all on-screen instructions.
Do not perform only a limited functional check. The automated pre-use process evaluates vital ventilator functions and provides calibration and status information before use.
Record:
- Whether the O₂ cell test passes
- Any displayed error code or message
- Whether the failure occurs immediately or after gas delivery begins
- Whether other gas-supply or transducer tests also fail
Expected outcome: The Servo-i completes the pre-use check without an O₂ cell or gas-delivery failure.
If the complete check passes, continue with an independent oxygen-concentration verification before release.
10. Verify Delivered FiO₂ Independently
Connect the ventilator to an approved test lung and a calibrated external oxygen analyzer.
Test several oxygen settings appropriate to the facility’s performance-verification procedure, such as:
- A setting near room-air concentration
- A midrange oxygen setting
- A high oxygen setting
Allow readings to stabilize before comparing the Servo-i display, selected FiO₂, and independent analyzer measurement.
Inspect the test setup for leaks or entrained room air that could falsely lower the analyzer reading.
Expected outcome: Measured oxygen concentration remains stable and within the manufacturer’s applicable performance tolerance.
If the displayed or delivered FiO₂ remains inaccurate, remove the ventilator from service.
11. Evaluate Whether the Problem Follows the Cell
When facility policy permits, compare performance using a verified compatible O₂ cell or evaluate the suspect cell in another approved test setup.
- If the failure follows the cell, replace the cell.
- If the failure remains with the ventilator, suspect the sensor interface, gas-blending system, pneumatic components, or internal electronics.
Do not repeatedly substitute parts without documenting each test result.
Expected outcome: Testing distinguishes a failed consumable sensor from a ventilator-side fault.
12. Complete Final Safety Verification
Before returning the Servo-i to clinical service:
- Confirm the full pre-use check passes.
- Verify delivered FiO₂ with a calibrated external analyzer.
- Test applicable oxygen and gas-supply alarms.
- Confirm displayed values are stable.
- Inspect hoses and connections.
- Confirm no unusual heat, odor, sound, or leakage is present.
- Restore the approved clinical configuration.
Expected outcome: Oxygen delivery, oxygen monitoring, alarms, and overall ventilator operation are verified as safe and accurate.
If the Problem Persists
If the O₂ cell calibration continues to fail or delivered FiO₂ remains inaccurate after verifying gas sources, hoses, connections, environmental conditions, sensor installation, sensor age, and an approved replacement cell, common external causes have been ruled out.
The problem may involve the internal oxygen-sensor interface, gas-blending system, pneumatic assembly, internal wiring, or control electronics.
The ventilator should be:
- Removed from service
- Labeled Out of Service
- Sent for authorized repair or bench evaluation
Do not return the Servo-i to patient use based only on a normal displayed value. Both the complete pre-use check and independent oxygen verification must pass. Knowing when to stop and escalate is proper troubleshooting.
Clinical Use Tip
Never troubleshoot questionable oxygen delivery on an active patient. Transfer the patient first and verify oxygenation independently. A plausible FiO₂ display does not prove that the delivered oxygen concentration is accurate.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Respiratory therapy reported that the Getinge Servo-i failed O₂ cell calibration and displayed FiO₂ values that did not match the selected oxygen setting."
Cause
What was observed during troubleshooting.
Example:
"Testing found an aged O₂ cell with unstable output; facility air and oxygen supplies, hoses, fittings, and accessible connections tested normally."
Resolution
What action was taken.
Example:
"Replaced the O₂ cell with an approved component, completed the full pre-use check, and verified delivered FiO₂ at multiple settings with a calibrated oxygen analyzer; unit passed and was returned to service."
Helpful Details to Include (If Known)
- Exact alarm or calibration message recorded
- Complete pre-use check result
- Oxygen outlet tested
- Air outlet tested
- Gas hoses inspected or swapped
- Hose connections verified
- O₂ cell installation date reviewed
- O₂ cell reseated or replaced
- Replacement part information documented
- Independent oxygen analyzer used
- FiO₂ settings and measured results recorded
- Alarm behavior verified
- Indicator lights observed
- Unusual sounds noted
- Unusual heat or smell noted
- Final device status documented
Final Thought
Accurate FiO₂ is essential to patient safety. Begin with gas supplies, hoses, connections, and sensor condition before suspecting internal failure. Complete pre-use testing, independent oxygen verification, appropriate escalation, and clear CCR documentation demonstrate sound Clinical Engineering practice.
That is successful troubleshooting.