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What This Guide Helps With
Troubleshooting CO2 sampling issues caused by blocked, leaking, kinked, disconnected, or improperly installed sampling lines.
Step-by-Step Troubleshooting
Ensure Patient Safety First
If the Philips NM3 is actively monitoring a patient, confirm that clinical staff are aware of the CO2 monitoring issue.
If EtCO2, respiration rate, or apnea monitoring is clinically required, move the patient to another working monitor or alternate approved monitoring method before troubleshooting.
Expected outcome: Patient ventilation monitoring remains continuous and safe.
Why it matters: A sampling line problem can prevent accurate EtCO2 readings and may delay recognition of respiratory compromise.
Verify the Reported Problem
Confirm the exact issue reported by staff. Look for symptoms such as:
- No EtCO2 value
- Low or unstable EtCO2 readings
- No CO2 waveform
- Intermittent waveform
- Sampling line blocked message
- Sampling line disconnected or leak-related message
- Pump noise or reduced sampling flow
Expected outcome: The problem is confirmed before parts are replaced or the monitor is removed from service.
If the issue is not present during testing, document that the reported condition could not be duplicated and continue checking external causes.
Inspect the Sampling Line Connection at the Monitor
Check that the sampling line is fully seated in the NM3 CO2 inlet connection.
Remove and reconnect the sampling line if needed. Make sure the connector is not loose, cracked, contaminated, or partially inserted.
Expected outcome: The line connects firmly and the monitor begins sampling normally.
If this resolves the issue, return the device to service after confirming stable CO2 operation. Stop troubleshooting.
Inspect the Full Length of the Sampling Line
Follow the sampling line from the monitor to the patient connection.
Look for:
- Kinks
- Pinched tubing
- Crushed sections
- Fluid contamination
- Loose fittings
- Cracks or splits
- Disconnected patient end
- Tubing trapped under equipment, bed rails, or bedding
Expected outcome: The sampling path is open, connected, and free of obvious damage.
Why it matters: A kinked or blocked sampling line can stop the monitor from pulling an adequate CO2 sample.
Replace the Sampling Line
Install a new compatible sampling line.
Do not try to reuse a line that is wet, visibly contaminated, kinked, cracked, or suspected of being blocked.
Expected outcome: CO2 sampling resumes with a stable waveform and EtCO2 value.
If replacing the sampling line resolves the issue, document the defective or blocked disposable and return the monitor to service. Stop troubleshooting.
Check for Moisture or Secretions in the Line
Inspect the removed sampling line for condensation, fluid, secretions, or visible blockage.
If moisture or contamination is present, discard the line and use a new compatible line.
Expected outcome: The replacement line remains dry and sampling is restored.
Why it matters: Moisture or secretions can block the sampling path and cause flow-related alarms or inaccurate CO2 readings.
Check the Patient Connection or Airway Adapter
Inspect the cannula, airway adapter, or sample port connection depending on how the NM3 is being used.
Confirm that the patient end is properly connected, not obstructed, and not installed in a way that blocks sample flow.
Expected outcome: The sampling line has a clear path from the patient source to the monitor.
If the patient connection was loose or incorrect and correcting it restores normal CO2 readings, stop troubleshooting.
Check for Leaks at Fittings and Adapters
Inspect all external CO2 sampling connections.
Gently move the line and fittings while watching the waveform and EtCO2 value.
Look for readings that drop out when the line is moved.
Expected outcome: CO2 readings remain stable when the tubing and connections are gently moved.
Why it matters: Small leaks can cause weak, unstable, or missing CO2 readings even when the line appears connected.
Confirm the Monitor Is Pulling Sample Flow
With a known-good sampling line installed, listen for normal sampling pump activity if applicable and observe whether the monitor detects the line and begins sampling.
Do not open the monitor or attempt internal pump repair during basic troubleshooting.
Expected outcome: The NM3 recognizes the line and produces a stable waveform when connected to an appropriate CO2 source.
Test With a Known-Good Setup
If available, compare the suspected monitor using:
- A new sampling line
- A known-good airway adapter or cannula
- A known-good patient simulator or approved CO2 test source
- Another monitor setup if available
Expected outcome: The issue follows the disposable accessory or external setup, not the monitor.
If the NM3 works normally with known-good accessories, replace the faulty disposable or external accessory and return the monitor to service. Stop troubleshooting.
Check for Repeated Failure With Multiple New Lines
If the same blocked, leak, kink, or disconnected condition appears with multiple new compatible sampling lines, suspect a monitor-side issue such as inlet damage, sensor module fault, flow restriction, or internal sampling pump problem.
Expected outcome: External causes are ruled out before removing the device from service.
If the Problem Persists
If the Philips NM3 continues to report sampling line blockage, leak, kink, or disconnection after using a new compatible sampling line and verifying all external connections, the likely cause is internal to the monitor or CO2 module.
Remove the device from service, label it Out of Service, and send it for bench evaluation or repair.
Do not continue troubleshooting on an active patient. Do not attempt internal disassembly unless following approved service procedures and facility policy.
Knowing when to stop is proper troubleshooting.
Clinical Use Tip
A CO2 sampling problem should be treated as a loss of ventilation monitoring. If the patient requires EtCO2 or respiration monitoring, clinical staff should move the patient to another working monitor before Clinical Engineering performs troubleshooting.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Staff reported the Philips NM3 was alarming for a blocked or disconnected sampling line and was not displaying a reliable CO2 waveform."
Cause
What was observed during troubleshooting.
Example:
"Found the CO2 sampling line kinked near the patient connection, preventing proper sample flow to the monitor."
Resolution
What action was taken.
Example:
"Replaced the sampling line, verified secure connection at the NM3, confirmed stable EtCO2 waveform, and returned the monitor to service."
Helpful Details to Include (If Known)
- Whether the issue occurred during active patient monitoring
- Exact alarm or message displayed
- Whether EtCO2 value was missing, low, or unstable
- Whether the CO2 waveform was absent or intermittent
- Sampling line condition
- Sampling line replaced
- Cannula or airway adapter checked
- Moisture, secretions, or blockage found
- Monitor inlet connection inspected
- Known-good sampling line tested
- Power behavior
- Environmental factors
- Indicator lights
- Final device status
Final Thought
Sampling line problems are often caused by simple external issues: loose connections, kinked tubing, blocked disposables, moisture, or damaged fittings. Clinical Engineering should rule those out first, protect patient monitoring, and escalate when the monitor still fails with known-good accessories. 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.