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What This Guide Helps With
This guide addresses situations where the Hamilton G5 ventilator:
- Displays an FiO₂ reading that does not match the set value
- Alarms for high or low oxygen concentration
- Delivers unexpected oxygen percentages
- Shows FiO₂ drift during ventilation
The focus is on ruling out external and easily verifiable causes first—gas supply, connections, setup, and configuration—before assuming internal mixer or sensor failure.
Step-by-Step Troubleshooting
1. Confirm Patient Safety First
- If the ventilator is actively supporting a patient, move the patient to another ventilator before troubleshooting.
- Do not attempt oxygen delivery troubleshooting while the device is in clinical use.
- This prevents unintended hypoxia or hyperoxia during testing.
2. Verify Wall Gas Supply
- Confirm oxygen and air hoses are connected to the correct wall outlets.
- Check that both supplies are fully inserted and locked.
- Confirm wall pressure is within normal range (typically ~50 psi in U.S. facilities).
- If available, connect to a known-good outlet.
Why this matters:
The G5 blends oxygen and medical air internally. If one source is absent, low, or cross-connected, the delivered FiO₂ will not match the set value.
3. Inspect Gas Hoses and DISS Fittings
- Check hoses for kinks, crushing, or damage.
- Inspect DISS fittings for debris or worn washers.
- Swap hoses with known-good hoses if uncertainty exists.
- A partially restricted air line, for example, can result in higher-than-set FiO₂.
4. Check for Crossed Gas Lines
- Confirm oxygen hose is connected to the oxygen inlet.
- Confirm air hose is connected to the air inlet.
- Trace hoses physically from wall to ventilator if necessary.
- Crossed gas lines are a common external cause of FiO₂ mismatch.
5. Run the Pre-Use Check / Calibration
- Perform a full system check per facility protocol.
- Allow the ventilator to complete oxygen sensor calibration.
- Observe if any gas supply or blending-related warnings appear.
- If the oxygen sensor calibration fails, this may indicate sensor drift or internal issue.
6. Verify Oxygen Sensor Status
- Check oxygen sensor age and service interval.
- If the sensor is near end-of-life, replace per facility policy.
- After replacement, repeat calibration and verify stability.
- A drifting or expired oxygen sensor can falsely indicate mismatch even when blending is correct.
7. Compare with External Oxygen Analyzer (If Available)
- Connect an external calibrated oxygen analyzer to the inspiratory limb.
- Compare displayed FiO₂ with ventilator reading.
- If:
- External analyzer matches the ventilator → likely gas supply issue upstream.
- External analyzer disagrees with ventilator → suspect internal sensor or calibration issue.
- This step helps differentiate measurement error from true blending error.
8. Check for Active Alarms or Messages
- Document any of the following:
- Low O₂ supply alarm
- Air supply alarm
- FiO₂ out-of-range
- Calibration failure
- Alarm behavior can help determine whether the issue is supply-related, sensor-related, or blending-related.
9. Observe Stability Over Time
- Set a fixed FiO₂ (e.g., 50%).
- Monitor reading for drift.
- Check if fluctuations correlate with supply pressure changes.
- Intermittent drift may suggest unstable supply pressure rather than internal failure.
If the Problem Persists
If:
- Gas supplies are verified and stable
- Hoses and fittings are confirmed good
- Oxygen sensor has been replaced or calibrated
- External analyzer confirms mismatch
Then the issue is likely internal to the ventilator (e.g., proportional solenoid valves, internal mixer, or flow control components).
- Remove the ventilator from service
- Label it Out of Service
- Send for bench evaluation or authorized repair
Knowing when to stop prevents unnecessary risk and avoids inappropriate internal disassembly.
Clinical Use Tip
Never troubleshoot oxygen blending on an actively ventilated patient.
Always transition the patient to another ventilator before testing gas supply or performing calibrations. Oxygen delivery errors directly affect patient safety and can cause rapid desaturation.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
“Respiratory therapist reported that the ventilator was set to 40% FiO₂ but displayed 55% and triggered high oxygen alarm.”
Cause
What was observed during troubleshooting.
Example:
“Air hose was partially kinked behind the equipment boom, restricting air supply and causing higher-than-set oxygen concentration.”
Resolution
What action was taken.
Example:
“Replaced air hose, verified supply pressures, recalibrated oxygen sensor, and confirmed FiO₂ accuracy with external analyzer. Ventilator passed system check and returned to service.”
Helpful Details to Include (If Known)
- Wall outlet pressures verified
- Hoses swapped with known-good set
- Oxygen sensor age noted
- External analyzer comparison performed
- Final operational status documented
Final Thought
Oxygen blending issues should always be approached logically: verify supply first, confirm measurement second, and escalate only after external causes are ruled out. Patient safety depends on accurate FiO₂ delivery, and disciplined troubleshooting protects both the patient and the equipment.
That is successful troubleshooting.