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What This Guide Helps With
Troubleshooting oxygen-supply alarms or incorrect delivered FiO₂ caused by gas sources, hoses, inlet connections, settings, accessories, or external supply problems.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not troubleshoot a suspected oxygen-delivery failure while the Puritan Bennett 980 is actively supporting a patient.
- Notify respiratory therapy and the clinical team immediately.
- Transfer the patient to another verified ventilator or approved ventilation method.
- Confirm adequate ventilation and oxygenation using appropriate independent clinical monitoring.
- Do not rely on the affected ventilator when delivered FiO₂ may be inaccurate.
Expected outcome: The patient is safely supported without depending on a ventilator with uncertain oxygen delivery.
Continue Clinical Engineering troubleshooting only after the PB980 has been removed from patient use.
2. Confirm the Exact Reported Problem
Review the alarm history and determine whether the problem involves:
- Loss of oxygen-supply pressure
- Intermittent oxygen-supply alarms
- Delivered FiO₂ higher or lower than the set value
- FiO₂ that fluctuates during ventilation
- Failure occurring only at higher oxygen settings
- Failure occurring only at one wall outlet or location
- A discrepancy between the PB980 reading and an external oxygen analyzer
Record the set oxygen percentage, displayed oxygen percentage, alarm wording, operating mode, and whether the condition is continuous or intermittent.
Expected outcome: The failure is clearly defined before parts or accessories are changed.
3. Verify Both Gas Sources Are Connected
Confirm that both medical-grade oxygen and compressed air are connected to the correct PB980 inlet fittings.
The PB980 mixes oxygen and air internally to produce the selected oxygen concentration. The manufacturer warns that relying on only one gas source can result in loss of ventilation or hypoxemia if that source fails.
- Verify that the oxygen hose is connected to the oxygen inlet.
- Verify that the air hose is connected to the air inlet.
- Confirm that both fittings are fully seated and locked.
- Check that the hoses have not been accidentally reversed.
- Confirm that no adapters are loose or partially connected.
Expected outcome: Both gas sources are securely connected to their correct inlets.
If reconnecting the hoses resolves the alarm and FiO₂ verifies correctly, complete functional testing and stop.
4. Check the Facility Oxygen Source
Test the oxygen outlet with an approved pressure gauge or known-good device according to facility policy.
Check for:
- No pressure at the wall outlet
- Low or unstable supply pressure
- A damaged or loose outlet
- A zone valve that is partially or fully closed
- Construction, maintenance, or medical-gas system work
- Failure affecting multiple devices in the same area
Do not assume the ventilator is defective until the facility oxygen source has been verified.
Expected outcome: The oxygen outlet provides stable pressure within the requirements listed for the installed PB980 configuration and hose system.
If the outlet is defective, remove it from clinical use and notify Facilities or the responsible medical-gas service.
5. Test the Ventilator at Another Approved Oxygen Outlet
Move the PB980 to a known-good medical-gas outlet when practical.
- Use the same ventilator and oxygen hose first.
- Observe whether the oxygen-supply alarm clears.
- Verify whether delivered FiO₂ becomes stable.
- Do not use an unapproved gas source or improvised adapter.
Expected outcome: The test separates a facility outlet problem from a ventilator or hose problem.
If the PB980 operates normally at another outlet, the original wall source is the likely cause. Stop ventilator troubleshooting and document the outlet issue.
6. Inspect the Oxygen Hose and Fittings
Disconnect the oxygen hose after safely isolating the gas supply and inspect it for:
- Kinks or crushing
- Cuts, abrasion, or deterioration
- Loose threaded fittings
- Damaged quick-connect fittings
- Bent or recessed connector components
- Contamination or debris
- Incorrect hose type
- Added adapters that may restrict flow
- Evidence of leaking gas
Verify that the hose is rated and approved for medical oxygen service.
Expected outcome: The oxygen hose and fittings are intact, unobstructed, correctly configured, and leak-free.
7. Substitute a Known-Good Oxygen Hose
Replace the oxygen hose with a compatible, approved, known-good hose.
Reconnect the PB980 to a verified oxygen source and observe:
- Oxygen-supply alarm status
- Stability of the displayed oxygen percentage
- Ability to reach the selected FiO₂
- Any audible gas leakage near the connections
Some hose assemblies may create excessive restriction at lower supply pressures, reducing ventilator performance.
Expected outcome: Normal operation with the replacement hose identifies the original hose or fitting as defective.
If the hose resolves the problem, remove the failed hose from service and stop.
8. Inspect the PB980 Oxygen Inlet Externally
Examine the ventilator oxygen inlet without opening the ventilator.
Check for:
- Physical damage
- Loose mounting
- Debris or contamination
- Damaged threads
- A connector that does not retain the hose
- Audible leakage
- Signs of impact or side-loading
- An incorrect or damaged inlet adapter
Do not insert tools into the gas inlet or attempt internal valve repair during basic troubleshooting.
Expected outcome: The inlet is secure, clean, undamaged, and retains the oxygen connection correctly.
Visible inlet damage requires removal from service and repair evaluation.
9. Verify the Set Oxygen Percentage
Confirm that the selected O₂ percentage matches the intended test condition.
Check for:
- An incorrect FiO₂ setting
- A recently changed patient profile
- A startup setting that was accepted unintentionally
- A setting changed during previous testing
- Confusion between the set value and monitored value
- An oxygen-enrichment or suction-related function affecting observations
The PB980’s mix module blends air and oxygen and uses an oxygen sensor to monitor the resulting mixture against the operator-selected O₂ setting.
Expected outcome: The selected oxygen percentage is appropriate and the monitored value is being interpreted correctly.
10. Inspect the Patient Circuit and Test Setup
Verify that the ventilator is connected to the correct circuit and test lung for the selected patient category.
Check for:
- Major circuit leaks
- Loose inspiratory or expiratory connections
- Incorrect circuit type
- Damaged circuit components
- An open nebulizer or accessory port
- Incorrectly installed filters
- An external gas source feeding into the circuit
- A sampling line or test analyzer connected incorrectly
Circuit or test-setup problems may create unstable readings or misleading analyzer results.
Expected outcome: The patient circuit and test setup are complete, sealed, and appropriate for testing.
11. Complete the Required Pre-Use or System Check
Run the PB980’s approved pre-use checkout or short self-test using the correct circuit and test equipment.
Do not bypass failed test steps.
Observe whether the ventilator identifies:
- Gas-supply problems
- Circuit leaks
- Flow-sensor problems
- Oxygen-sensor problems
- Internal pneumatic faults
- Calibration or system-check failures
Expected outcome: The ventilator completes the required checkout without gas-delivery or oxygen-monitoring failures.
If the checkout fails repeatedly after external causes are corrected, remove the ventilator from service.
12. Compare Delivered FiO₂ With an Independent Analyzer
Connect a calibrated oxygen analyzer according to facility test procedures.
Test several representative oxygen settings, such as:
- A low oxygen setting
- A midrange setting
- A high oxygen setting
Allow readings to stabilize before recording results. Use a controlled test lung and verify that both gas supplies remain stable during the test.
Compare:
- Set FiO₂
- PB980 monitored FiO₂
- Independent analyzer reading
- Stability over time
Expected outcome: The independent analyzer and ventilator reading remain within the applicable manufacturer performance specification and facility test tolerance.
A large or unstable discrepancy suggests an oxygen-sensor, gas-mixing, inlet-regulation, or internal pneumatic problem.
13. Evaluate Whether the Problem Follows the Gas Source
When safe and permitted, repeat the test using:
- A second verified wall oxygen source
- A known-good approved hose
- A verified air source
- A controlled cylinder source with an approved regulator, when allowed by policy
Change only one item at a time so the cause can be identified.
Expected outcome: The technician determines whether the failure follows the outlet, hose, gas source, or ventilator.
14. Review Alarm and Diagnostic Information
Record all active alarms, diagnostic codes, timestamps, and repeated failure patterns.
Determine whether the PB980 reports:
- Oxygen-supply loss
- Low gas pressure
- Oxygen-sensor failure
- Delivered oxygen outside the expected range
- Internal pneumatic failure
- Repeated startup or self-test failure
Do not clear diagnostic information before it has been documented.
Expected outcome: Sufficient information is preserved for bench troubleshooting, service support, or repair escalation.
15. Perform Final Functional Verification
If an external cause was corrected:
- Reconnect both verified gas sources.
- Run the required system checkout.
- Test ventilation with a test lung.
- Verify several oxygen settings with a calibrated analyzer.
- Confirm that displayed and audible alarms operate.
- Confirm stable operation for an appropriate observation period.
- Inspect for leaks, unusual sounds, heat, or odor.
Do not return the PB980 to service based only on the disappearance of an alarm.
Expected outcome: The ventilator passes all required functional and oxygen-delivery testing before release.
If the Problem Persists
If verified gas sources, wall outlets, hoses, connections, settings, circuit components, and test equipment have been ruled out, the problem is likely internal.
Possible internal causes may include the oxygen sensor, inlet regulation components, gas flow sensing, gas-mixing components, pneumatic valves, wiring, or control electronics.
The ventilator should be:
- Removed from service
- Labeled Out of Service
- Sent for qualified bench evaluation or authorized repair
- Accompanied by the recorded alarms, diagnostic codes, test conditions, and analyzer results
Do not continue operating a PB980 that cannot reliably deliver or verify the selected FiO₂. Knowing when to stop and escalate is proper troubleshooting.
Clinical Use Tip
Never troubleshoot uncertain oxygen delivery while the PB980 is connected to an active patient. Transfer the patient first and independently verify oxygenation on the replacement equipment.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Respiratory therapy reported repeated oxygen-supply alarms and delivered FiO₂ approximately 10% below the selected value."
Cause
What was observed during troubleshooting.
Example:
"The oxygen wall hose was internally restricted; the PB980 operated normally with a verified outlet and known-good replacement hose."
Resolution
What action was taken.
Example:
"Removed the defective oxygen hose from service, installed an approved replacement, completed system checkout, and verified multiple FiO₂ settings with a calibrated oxygen analyzer."
Helpful Details to Include (If Known)
- Patient removed before troubleshooting
- Exact alarm wording
- Alarm-history entries
- Set and monitored FiO₂
- Independent analyzer readings
- Oxygen outlet tested
- Oxygen-supply pressure
- Air supply verified
- Alternate outlet tested
- Oxygen hose swapped
- Hose or inlet damage
- Audible gas leakage
- Circuit and filter configuration
- System-check results
- Diagnostic codes
- Unusual sounds
- Unusual heat or smell
- Final device status
Final Thought
Oxygen-delivery complaints require immediate attention because inaccurate FiO₂ can directly affect patient safety. Verify external gas sources, hoses, settings, and test equipment logically before suspecting an internal failure. Escalate when oxygen delivery cannot be confidently verified, and document the complete troubleshooting path.
That is successful troubleshooting.