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What This Guide Helps With
Troubleshooting FilterLine disconnection, blockage, kink, leak, or recognition issues affecting CO₂ sampling on the Capnostream 35.
Step-by-Step Troubleshooting
Ensure Patient Safety First
If the Capnostream 35 is actively monitoring a patient, confirm that clinical staff are aware CO₂ monitoring may be interrupted or unreliable.
If EtCO₂ monitoring is clinically required, move the patient to another working monitor or use another approved monitoring method before troubleshooting.
Expected outcome: Patient ventilation monitoring continues safely.
Why it matters: A disconnected or blocked FilterLine can prevent accurate EtCO₂, respiration rate, apnea, and no-breath monitoring.
Verify the Reported Message or Behavior
Confirm the exact message or symptom reported by staff. Look for messages such as FilterLine disconnected, FilterLine blocked, no FilterLine detected, no CO₂ waveform, absent EtCO₂ value, or no respiration rate.
Observe whether the issue occurs immediately after connecting the FilterLine, during patient movement, during transport, or after the device has been running for a while.
Expected outcome: The reported issue is confirmed and the failure pattern is understood.
If the issue cannot be duplicated: Document the check and return the unit only if it passes functional verification.
Inspect the FilterLine Connection at the Monitor
Remove and reconnect the FilterLine at the Capnostream 35. Make sure it is fully seated and not cross-threaded, loose, or partially inserted.
Check for debris, damage, moisture, or cracked plastic at the connection point.
Expected outcome: The monitor recognizes the FilterLine and CO₂ sampling resumes.
If this resolves the issue, stop troubleshooting and document the correction.
Inspect the Entire FilterLine Tubing Path
Trace the FilterLine from the monitor to the patient end. Look for kinks, crushing, tight bends, pinched tubing under bed rails, trapped tubing in stretcher side rails, or tubing pulled tight during repositioning.
Expected outcome: The tubing path is clear and open.
Why it matters: A physical restriction can trigger blockage alarms or prevent accurate sampling.
Replace the FilterLine With a Known-Good Compatible Line
Install a new, compatible Medtronic FilterLine appropriate for the patient setup.
Do not reuse a visibly contaminated, wet, kinked, cracked, or damaged line.
Expected outcome: The monitor detects the new FilterLine and displays a stable CO₂ waveform when connected to a breathing patient or approved simulator.
If this resolves the issue, stop troubleshooting and document the defective or blocked disposable line.
Check for Moisture or Contamination
Inspect the removed FilterLine for visible fluid, condensation, secretions, blood, medication residue, or contamination.
If moisture or contamination is present, discard the line and verify function with a new one.
Expected outcome: The replacement line allows normal CO₂ sampling.
Why it matters: Fluid or contamination can block the sampling path and may damage the monitor if ignored.
Check the Patient-End Connection
Verify that the cannula, airway adapter, or sampling connection is properly placed and connected.
For intubated patients, confirm the airway adapter is correctly installed in the breathing circuit and not blocked by secretions or condensation.
For nasal/oral cannulas, confirm the cannula is positioned correctly and not folded, pulled away, or blocked.
Expected outcome: The patient-end sampling point is open and correctly positioned.
If this resolves the issue, stop troubleshooting and document the setup correction.
Check for Incorrect Accessory or Incompatible Line
Confirm the installed line is the correct type for the Capnostream 35 and the patient application.
Look for off-brand, damaged, expired, modified, or incorrect sampling accessories that may not be recognized or may restrict flow.
Expected outcome: A compatible FilterLine is installed and recognized by the monitor.
Why it matters: Capnography monitors depend on the correct sampling accessory to maintain proper flow and measurement accuracy.
Power Cycle the Monitor Only When Safe
If the FilterLine is known-good and properly connected but still not recognized, remove the unit from patient use if needed and restart the monitor.
After restart, reconnect the FilterLine and observe whether the same message returns.
Expected outcome: The monitor initializes normally and recognizes the FilterLine.
If the error clears: Perform a functional check before returning the device to service.
Perform a Basic CO₂ Functional Check
Using an approved CO₂ simulator or known-good test setup, verify that the Capnostream 35 detects the FilterLine, pulls sample flow, displays a CO₂ waveform, and reports EtCO₂ and respiration rate appropriately.
Expected outcome: CO₂ monitoring operates normally with a known-good line and test source.
If the monitor fails with a known-good FilterLine and test setup: Treat the issue as likely internal.
If the Problem Persists
If the Capnostream 35 still reports a disconnected, blocked, or unrecognized FilterLine after checking the connection, tubing path, patient-end setup, compatible accessories, replacement FilterLine, and basic functional operation, common external causes have been ruled out.
Remove the device from service, label it Out of Service, and send it for repair or bench evaluation.
Possible internal concerns may include a damaged FilterLine connector, internal sampling pump issue, flow sensor problem, occlusion detection fault, or CO₂ module failure. Do not continue repeated bedside troubleshooting once a known-good setup has failed.
Knowing when to stop is proper troubleshooting.
Clinical Use Tip
Do not troubleshoot FilterLine or sampling issues while relying on that same monitor for active respiratory monitoring. Move the patient to another working monitor first if EtCO₂, respiration rate, apnea, or no-breath monitoring is needed.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Clinical staff reported the Capnostream 35 displayed a FilterLine blocked/disconnected message and was not showing a CO₂ waveform."
Cause
What was observed during troubleshooting.
Example:
"Found the installed FilterLine kinked under the stretcher rail and unable to sample properly."
Resolution
What action was taken.
Example:
"Replaced the FilterLine, corrected tubing routing, verified CO₂ waveform and EtCO₂ reading with functional check, and returned the monitor to service."
Helpful Details to Include (If Known)
- Exact FilterLine message displayed
- Whether CO₂ waveform was missing or intermittent
- Whether EtCO₂ or respiration rate was blank, dashed, or unstable
- FilterLine type used
- Whether the line was kinked, blocked, wet, or contaminated
- Whether a known-good FilterLine was tested
- Patient-end connection checked
- Monitor connector inspected
- Power behavior during restart or power cycle
- Environmental factors such as transport, bed rail position, stretcher rail position, or patient movement
- Indicator lights, screen messages, or alarm behavior observed
- CO₂ functional check performed
- Final device status
Final Thought
FilterLine issues are often caused by simple external problems such as loose connections, kinked tubing, blocked disposable lines, moisture, or incorrect accessories. Clinical Engineering should rule out these causes first, protect patient monitoring during the process, and escalate the device when a known-good setup still fails. Clear CCR documentation helps show what was checked, what was found, and why the device was returned to service or removed for repair.
That is successful troubleshooting.