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What This Guide Helps With
No EtCO2 value or capnogram appears because of sampling-line blockage, loose connections, moisture, consumables, positioning, or sampling-system problems.
Step-by-Step Troubleshooting
1. Protect the Patient and Maintain Ventilation Monitoring
If capnography is clinically required, provide another verified method of EtCO2 or ventilation monitoring before troubleshooting the affected channel.
Do not troubleshoot an unreliable capnography system while a patient depends solely on it.
Expected outcome: Required ventilation monitoring continues throughout evaluation.
2. Confirm the Exact Capnography Complaint
Determine whether the reported issue is:
- No EtCO2 value
- No capnogram
- Sampling line not recognized
- Intermittent waveform
- Weak or delayed waveform
- Repeated sampling interruption
- Problem occurring only with a particular airway setup
Use an appropriate capnography simulator or gas source when available.
Expected outcome: The specific sampling or display failure is identified.
3. Inspect the Sampling Line and Consumables
Check the external sampling path for:
- Kinks
- Crushed tubing
- Moisture
- Secretions
- Loose fittings
- Cracked tubing
- Occlusion
- Incorrect or incompatible consumables
Replace blocked, contaminated, or damaged single-use components rather than attempting to clear them for reuse when not intended.
Expected outcome: The sampling path is clean, open, intact, and properly connected.
4. Verify Airway Adapter or Sampling Connection
Inspect the patient-end connection for secure placement and proper orientation.
Check whether the sampling inlet is positioned where exhaled gas can reliably reach it.
Expected outcome: Exhaled gas can enter the sampling system without a loose connection or obvious leak.
5. Reseat the Sampling-Line Connection
Disconnect and reconnect the line at the Propaq MD sampling port and patient-side connection as appropriate.
Inspect accessible connectors for contamination or damage.
Expected outcome: The sampling connection is secure and the device begins displaying a consistent capnogram. If normal operation returns, complete verification and troubleshooting can stop.
6. Substitute a Known-Good Sampling Line
Install a new or known-good compatible sampling line and associated consumables.
Do not assume an internal pump failure until the disposable sampling path has been eliminated.
Expected outcome: If the waveform and EtCO2 value return with the replacement line, the original consumable was the cause and troubleshooting can stop after verification.
7. Check for Moisture or Secretion Recurrence
If lines repeatedly obstruct, evaluate whether clinical setup, excessive moisture, secretion burden, or placement is contributing.
Do not bypass moisture-management components or modify the sampling system.
Expected outcome: The cause of repeated external blockage is corrected without altering the approved sampling configuration.
8. Test With Approved Capnography Test Equipment
Use an appropriate simulator or controlled CO2 source to verify:
- Gas sampling
- Capnogram display
- EtCO2 value
- Respiratory rate when applicable
- Stability over repeated breaths or cycles
Expected outcome: Stable simulated capnography confirms correct system operation.
9. Perform Final Functional Verification
After correction:
- Confirm sampling begins reliably
- Confirm capnogram is stable
- Confirm EtCO2 value is displayed
- Confirm the sampling path remains unobstructed
- Confirm applicable alarms respond appropriately
Expected outcome: Capnography operates consistently without sampling interruption. Troubleshooting can stop.
10. Escalate Persistent Sampling Failure
If the unit does not sample correctly with a verified external setup and known-good line, remove it from service.
Expected outcome: An internal pump, flow path, sensor, interface, configuration, or other service-level condition is evaluated by qualified personnel.
If the Problem Persists
Once sampling lines, airway adapters, moisture, secretions, connections, positioning, compatible consumables, and external test conditions have been ruled out, the remaining cause may involve the internal sampling system, sensing system, flow control, configuration, or another service-level condition.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for repair or bench evaluation
- Evaluated using appropriate manufacturer documentation and approved test equipment
- Repaired or configured only by qualified personnel
Following service, complete applicable EtCO2, alarm, monitoring, defibrillator, and electrical safety testing before release.
Knowing when to stop external troubleshooting is proper troubleshooting.
Clinical Use Tip
Maintain alternate ventilation monitoring whenever the capnogram or EtCO2 value is unreliable or absent.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Clinical staff reported no EtCO2 waveform despite the sampling line being connected to the Propaq MD."
Cause
What was observed during troubleshooting.
Example:
"Clinical Engineering found the sampling line obstructed by moisture and confirmed normal operation with a known-good replacement line."
Resolution
What action was taken.
Example:
"The blocked sampling line was replaced and stable capnogram, EtCO2 values, and alarm operation were verified with approved test equipment."
Helpful Details to Include (If Known)
- Capnogram present or absent
- EtCO2 value behavior
- Sampling line condition
- Moisture or secretions observed
- Airway adapter condition
- Connector condition
- Known-good line result
- Simulator or gas-source result
- Alarm behavior
- Whether failure was intermittent
- Final device status
Final Thought
Maintain ventilation monitoring, inspect and substitute the complete external sampling path before suspecting the device, verify capnography with controlled test equipment, escalate unresolved failures, and document both the external cause and final performance.
That is successful troubleshooting.