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What This Guide Helps With
Troubleshooting failed O₂ sensor calibration or inaccurate displayed FiO₂ caused by gas supply, connections, calibration conditions, settings, or sensor failure.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not troubleshoot unreliable oxygen delivery or measurement while the HAMILTON-C6 is actively supporting a patient.
- Notify respiratory therapy and the clinical team.
- Transfer the patient to another verified ventilator or approved ventilation method.
- Use independent oxygen monitoring when clinically required.
- Confirm that the replacement ventilator is delivering the prescribed oxygen concentration.
Expected outcome: The patient is safely supported without relying on uncertain FiO₂ delivery or monitoring.
Continue Clinical Engineering troubleshooting only after the ventilator has been removed from patient use.
2. Confirm the Exact Failure
Review the displayed alarm, message, and alarm history.
Determine whether:
- O₂ sensor calibration will not begin.
- Calibration starts but fails.
- An O₂ sensor calibration needed alarm is displayed.
- Measured oxygen differs from the set FiO₂.
- The reading is unstable, delayed, or fixed at one value.
- The issue occurs only at higher oxygen settings.
- The problem began after a gas-supply, sensor, or configuration change.
Record the set FiO₂, displayed oxygen value, gas-source status, and exact message.
Expected outcome: The failure pattern is clearly identified before components are changed.
3. Verify the Oxygen Supply
Confirm that the oxygen hose is:
- Connected to the correct ventilator inlet.
- Fully seated at both the ventilator and wall or cylinder source.
- Free of kinks, crushing, damage, and obvious leakage.
- Not crossed with the compressed-air hose.
Verify the oxygen source has adequate pressure and is not empty, shut off, or intermittently failing. When permitted, test the outlet using an approved gas-pressure analyzer or a known-good device.
An inadequate oxygen source can cause both calibration failure and incorrect delivered FiO₂.
Expected outcome: A stable oxygen supply is available at the ventilator inlet.
If correcting the gas supply resolves the issue, repeat the required preoperational checks and stop troubleshooting.
4. Check the Air Supply
Verify that the compressed-air connection is also correct and stable.
Incorrect air pressure, a crossed hose, or loss of one gas source can affect the ventilator’s oxygen blending and make the displayed or measured FiO₂ appear incorrect.
Expected outcome: Both required gas sources are correctly connected and available.
5. Inspect External Gas Connections
Inspect the oxygen and air fittings for:
- Loose connections
- Damaged threads or couplings
- Contamination
- Bent or damaged fittings
- Audible leakage
- Incorrect adapters
- Excessive tension on the hoses
Substitute known-good, compatible gas hoses when available.
Expected outcome: The ventilator receives gas through secure, undamaged connections.
If replacing a defective hose or fitting restores normal operation, complete operational verification and stop.
6. Verify the Oxygen Setting and Alarm Limits
Confirm that the selected oxygen concentration matches the intended test value.
Review:
- Set Oxygen or FiO₂ value
- Oxygen alarm limits
- Active ventilation mode
- Any automated oxygen-control features
- Patient-category and configuration settings
Ensure the complaint is not caused by comparing the measured oxygen value with an outdated prescription, previous patient setup, or automatically adjusted setting.
Expected outcome: The intended oxygen setting and alarm configuration are confirmed.
7. Allow Adequate Stabilization Time
After connecting gas supplies or changing the oxygen setting, operate the ventilator on an approved test lung and allow the oxygen concentration to stabilize.
A brief difference between the set and displayed value may occur immediately after startup or a major FiO₂ adjustment. Persistent or excessive deviation requires further evaluation.
Expected outcome: The displayed oxygen value stabilizes near the selected setting.
8. Prepare the Ventilator for O₂ Sensor Calibration
Place the ventilator in the condition required by its installed software and sensor configuration. Follow the on-screen calibration instructions exactly.
Before starting:
- Confirm both gas supplies are stable.
- Confirm there are no active gas-supply alarms.
- Use the correct patient circuit and test lung.
- Ensure the circuit is assembled without major leaks.
- Confirm the ventilator is not connected to a patient.
- Allow the O₂ sensor sufficient warm-up time when applicable.
The HAMILTON-C6 includes an O₂ sensor calibration function and can generate an O₂ sensor calibration needed alarm when calibration is required.
Expected outcome: The ventilator is in a stable and appropriate condition for calibration.
9. Run the O₂ Sensor Calibration
Initiate the O₂ sensor calibration from the appropriate System, Tests & Calib, or preoperational-check screen for the installed software version.
Follow all displayed prompts without disconnecting gas supplies or changing settings during calibration.
Expected outcome: Calibration completes successfully and the calibration-needed message clears.
If calibration succeeds, continue to independent FiO₂ verification before returning the ventilator to service.
10. Repeat Calibration After Correcting External Conditions
If calibration fails:
- Reconfirm oxygen and air source pressures.
- Reseat both gas hoses.
- Check for active supply alarms.
- Allow additional sensor stabilization time.
- Restart the calibration once.
Do not repeatedly calibrate a sensor without correcting the condition causing the failure.
Expected outcome: A temporary connection, pressure, or stabilization issue is corrected.
11. Inspect the Accessible O₂ Sensor Area
With the ventilator powered down and removed from service, inspect only externally accessible sensor-related areas permitted by facility procedure.
Look for:
- A loose or improperly seated accessible sensor
- Contamination or moisture
- Damaged accessible contacts
- Signs of corrosion
- Incorrect sensor type
- Evidence that the sensor was recently replaced or disturbed
Do not perform deep internal disassembly or board-level troubleshooting.
Expected outcome: No external sensor seating or contamination problem remains.
12. Compare Delivered FiO₂ With an Independent Analyzer
Connect the ventilator to a suitable test lung and calibrated oxygen analyzer.
Test several clinically relevant oxygen settings, such as:
- Approximately 21%
- An intermediate concentration
- A high oxygen concentration
Allow the reading to stabilize at each setting. Compare the independent analyzer reading with the set and displayed FiO₂.
Use the manufacturer’s applicable specifications and facility test procedure to determine acceptance.
Expected outcome: Delivered oxygen tracks the selected concentration within the permitted tolerance.
If the external analyzer agrees with the set value but the ventilator display does not, suspect an O₂ sensing or calibration problem.
If both the external analyzer and ventilator indicate incorrect oxygen delivery, suspect a gas-source, mixer, valve, or internal pneumatic problem.
13. Test With a Known-Good Approved O₂ Sensor When Authorized
When the installed sensor is a replaceable item and facility policy permits, substitute a known-good Hamilton-approved compatible O₂ sensor.
Repeat:
- O₂ sensor calibration
- Preoperational checks
- Independent FiO₂ testing
Do not install an unapproved or incompatible sensor.
Expected outcome: Calibration and FiO₂ accuracy return to normal with the known-good sensor.
If replacement resolves the issue, document the failed sensor and complete all required functional testing before return to service.
14. Perform the Complete Preoperational Check
After any adjustment, hose substitution, calibration, or sensor replacement, perform the complete manufacturer-required preoperational check.
Verify:
- Gas supplies
- Circuit tightness
- Flow-sensor function
- O₂ sensor calibration
- Alarm operation
- Delivered oxygen concentration
- Stable ventilation on a test lung
Expected outcome: All required tests pass without alarms or abnormal oxygen readings.
If any required check fails, do not return the ventilator to clinical use.
If the Problem Persists
If gas sources, hoses, settings, circuit conditions, calibration preparation, and the accessible O₂ sensor have been evaluated, the common external causes have been ruled out.
The problem may involve:
- A failed O₂ sensor
- Internal sensor wiring or connection
- Oxygen blender or mixer malfunction
- Internal pneumatic valve failure
- Gas-pressure measurement error
- Control or acquisition electronics
- Software or calibration-data fault
The ventilator should be:
- Removed from service
- Labeled Out of Service
- Sent for qualified repair or bench evaluation
- Evaluated using the applicable Hamilton service documentation and approved test equipment
Knowing when to stop external troubleshooting and escalate the device is proper Clinical Engineering practice.
Clinical Use Tip
Never rely solely on the ventilator’s displayed FiO₂ when oxygen delivery is in question. Remove the patient from the affected ventilator and verify oxygen concentration with an independent calibrated analyzer before returning the unit to service.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Respiratory therapy reported that the HAMILTON-C6 failed O₂ sensor calibration and displayed an FiO₂ value lower than the selected oxygen setting."
Cause
What was observed during troubleshooting.
Example:
"Verified stable wall air and oxygen supplies, then found that the installed O₂ sensor continued to fail calibration and produced unstable readings during independent oxygen testing."
Resolution
What action was taken.
Example:
"Removed the ventilator from service, replaced the approved O₂ sensor, successfully completed calibration and preoperational testing, and verified delivered FiO₂ with a calibrated oxygen analyzer."
Helpful Details to Include (If Known)
- Exact alarm or calibration message
- Set FiO₂ and displayed FiO₂
- Independent analyzer reading
- Oxygen outlet tested
- Air outlet tested
- Gas-source pressures
- Gas hoses swapped
- Gas fittings inspected
- Calibration attempted
- Calibration result
- Sensor warm-up time
- Sensor replaced or reseated
- Test settings used
- Alarm behavior
- Indicator lights
- Unusual sounds
- Unusual heat or smell
- Preoperational-check result
- Final device status
Final Thought
Oxygen-related faults require careful patient-safety decisions and objective testing. Verify external gas sources and connections first, follow the calibration prompts, confirm delivered FiO₂ independently, and escalate when calibration or accuracy cannot be restored. Complete CCR documentation provides a clear record of the complaint, findings, corrective action, and final equipment status.
That is successful troubleshooting.