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What This Guide Helps With
Troubleshooting absent, intermittent, or unreliable EtCO₂ sampling caused by sampling lines, airway adapters, moisture, blockage, connections, or monitor faults.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not troubleshoot an unresolved EtCO₂ sampling problem while the LIFEPAK 35 is being relied upon for active patient monitoring.
If continuous capnography is clinically required, move the patient to another verified monitoring method or known-good device before continuing.
Expected: Patient care is not dependent on unreliable EtCO₂ monitoring.
Why it matters: The LIFEPAK 35 is intended to provide capnography among its monitoring functions, so an unresolved sampling failure can affect respiratory monitoring reliability.
2. Confirm the Reported Failure
Power on the LIFEPAK 35 and determine the exact behavior:
- No EtCO₂ value
- No capnogram waveform
- Intermittent waveform
- Unexpectedly low or unstable reading
- Sampling-related message or alarm
- Failure only with a specific patient circuit or accessory
Record any exact on-screen message before clearing or restarting the device.
Expected: The failure is clearly identified and reproducible.
If normal EtCO₂ operation returns and remains stable, document the findings and stop.
3. Verify Capnography Is Active and Displayed
Confirm the device is configured to display the CO₂ parameter and capnogram as expected.
Check that:
- The correct patient monitoring mode is active
- The CO₂ parameter is not intentionally disabled or omitted from the current display configuration
- The waveform area and numeric field are available
Expected: EtCO₂ monitoring is enabled and the display is configured to show the parameter.
Why it matters: A display or configuration issue can resemble sampling failure even when the hardware path is functional.
4. Inspect the Sampling Line
Examine the complete EtCO₂ sampling line for:
- Kinks
- Crushing
- Tight bends
- Disconnection
- Cracks
- Contamination
- Visible fluid
- Occlusion
- Damaged connectors
Straighten the tubing and reseat all accessible connections.
Expected: The sampling path is open, dry, intact, and securely connected.
If the issue resolves, replace any questionable disposable component, verify stable operation, and stop.
5. Check for Moisture or Secretions
Inspect the sampling line and patient-side connection for:
- Condensation
- Water
- Mucus
- Blood
- Nebulized medication residue
- Other visible contamination
Do not attempt to restore a contaminated disposable sampling line by forcing air through it.
Replace the affected disposable sampling component with a compatible new one.
Expected: A clean, unobstructed sampling path is established.
If normal waveform and EtCO₂ values return, the contaminated sampling component was the likely cause; stop.
6. Inspect the Airway Adapter or Cannula
For intubated monitoring, inspect the airway adapter and sampling connection for:
- Loose attachment
- Incorrect orientation
- Blocked sampling port
- Condensation
- Secretions
- Cracked fittings
For non-intubated monitoring, inspect the cannula for:
- Correct positioning
- Crushed tubing
- Occluded nasal prongs
- Disconnection
- Excessive movement
Expected: The patient-side sampling accessory is correctly positioned and unobstructed.
7. Verify the Sampling Line Is Fully Seated at the LIFEPAK 35
Disconnect and reconnect the sampling line at the monitor-side CO₂ connection according to normal accessory handling practices.
Inspect externally for:
- Incomplete insertion
- Loose fit
- Bent or damaged connector features
- Foreign material
- Visible contamination
Do not insert tools or probes into the device sampling inlet.
Expected: The sampling line seats securely without looseness or visible damage.
8. Substitute a Known-Good Compatible Sampling Set
Replace the complete sampling line and applicable patient-side adapter or cannula with a known-good compatible set.
Do not change multiple device settings at the same time.
Expected: The LIFEPAK 35 produces a stable capnogram and EtCO₂ value with the replacement sampling set.
If the issue resolves, the original sampling accessory was faulty or obstructed; stop.
Stryker provides dedicated LIFEPAK 35 capnography training and accessory resources, supporting verification of the intended capnography setup and compatible accessory path.
9. Determine Whether the Failure Follows the Accessory or the Monitor
Using controlled bench evaluation:
- Test the suspect sampling set only if it is safe and appropriate to do so
- Test the LIFEPAK 35 with a verified compatible sampling set
- Compare behavior without involving an active patient
Expected:
- Failure follows the sampling set → replace accessory
- Failure remains with the LIFEPAK 35 → continue device evaluation
Why it matters: This separates an external disposable-path failure from a likely monitor-side fault.
10. Power Cycle the Device Under Controlled Conditions
After recording any active message or failure behavior:
- Disconnect the device from patient use.
- Shut down normally.
- Wait briefly.
- Restart the LIFEPAK 35.
- Reconnect a known-good sampling setup.
- Observe EtCO₂ initialization and waveform behavior.
Expected: Capnography initializes normally and remains stable.
If the failure returns, do not repeatedly power cycle the unit as a substitute for repair.
11. Perform a Controlled Capnography Functional Evaluation
Use the facility’s approved test equipment and current Clinical Engineering procedure to evaluate capnography performance.
Verify, as applicable:
- CO₂ detection
- Waveform generation
- Numeric EtCO₂ response
- Stability
- Alarm behavior
- Recovery after accessory reconnection
Stryker specifically lists a LIFEPAK 35 Performance evaluation – Capnography resource, making a controlled capnography functional check appropriate before return to service.
Expected: The unit passes the complete approved capnography evaluation.
If the unit does not pass, stop troubleshooting and escalate.
If the Problem Persists
If a known-good compatible sampling set, airway accessory, connection check, configuration review, controlled restart, and approved capnography evaluation do not restore reliable EtCO₂ operation, common external causes have been ruled out.
The issue is likely within the monitor-side capnography path or associated internal electronics.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for repair or bench evaluation
Do not continue into internal pneumatic-path, module, PCB, or component-level repair unless performed under authorized service procedures with appropriate training and test equipment.
Knowing when to stop is proper troubleshooting.
Clinical Use Tip
Do not troubleshoot unreliable EtCO₂ sampling on an active patient. Transfer respiratory monitoring to another verified method first, then evaluate the LIFEPAK 35 under controlled conditions.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Clinical staff reported the LIFEPAK 35 displayed no reliable EtCO₂ value or capnogram during patient monitoring."
Cause
What was observed during troubleshooting.
Example:
"Inspection found the EtCO₂ sampling line obstructed by visible moisture, preventing reliable gas sampling."
Resolution
What action was taken.
Example:
"Removed the contaminated sampling set, installed a compatible replacement, and verified stable capnogram and EtCO₂ response during functional testing."
Helpful Details to Include (If Known)
- Exact on-screen CO₂ message recorded
- Failure reproduced
- CO₂ parameter/display configuration checked
- Sampling line inspected
- Sampling line swapped
- Airway adapter or cannula checked
- Moisture or secretions observed
- Monitor-side connection inspected
- Known-good compatible accessory tested
- Alarm behavior verified
- Capnography functional evaluation completed
- Unusual sounds noted
- Unusual heat or smell noted
- Final device status documented
Final Thought
EtCO₂ sampling failures are often caused by external problems such as obstruction, moisture, damaged tubing, poor connections, or defective disposables. Patient safety comes first, followed by logical isolation of the sampling path. When known-good accessories and controlled functional testing do not restore reliable operation, remove the LIFEPAK 35 from service and escalate appropriately. Clear CCR documentation preserves both the technical findings and the final safety decision.
That is successful troubleshooting.