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What This Guide Helps With
Troubleshooting unavailable CO2 or anesthetic-agent measurements caused by sample-line, filter, water-trap, startup-test, accessory, or internal gas-sensor faults.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended gas-measurement troubleshooting while the Perseus is supporting an active patient.
If CO2 or anesthetic-agent monitoring becomes unavailable during a procedure:
- Alert the anesthesia provider immediately.
- Provide an approved independent gas-monitoring system or transfer the patient to another verified anesthesia machine.
- Maintain continuous oxygenation, ventilation, and appropriate anesthetic monitoring.
- Do not assume ventilation or agent delivery is safe solely because the machine continues operating.
Drager specifies that O2, CO2, and anesthetic gases must be monitored whenever the breathing system is used. If the internal patient-gas measurement module fails, an independent gas-measurement system is required.
Expected: Patient care is no longer dependent on the unavailable internal gas measurements.
If alternate monitoring or equipment resolves the immediate safety concern, continue troubleshooting off patient.
2. Confirm the Exact Failure Mode
Review what clinical staff observed and record the complete alarm message.
Determine whether:
- CO2 waveform and values are both absent.
- Anesthetic-agent values alone are unavailable.
- All patient-gas measurements are unavailable.
- Values appear briefly and then disappear.
- The failure began during startup, after circuit replacement, or during a case.
- The machine displays Sample line disconnected?, Sample line occluded, Water trap disconnected?, Water trap full, CO2 sensor accuracy low, or Gas sensor failure.
The Perseus identifies disconnected or blocked sampling components separately from internal gas-sensor failures.
Expected: The complaint is narrowed to a sampling-path problem, isolated measurement problem, or complete gas-analyzer failure.
If the reported condition was resolved after correcting an obvious disconnected sampling line, verify operation and stop.
3. Confirm Normal Power and Startup Status
With the machine removed from active patient use:
- Confirm the Perseus is connected to reliable AC power.
- Check for unrelated startup, power, temperature, or cooling alarms.
- Place the unit in Standby according to facility procedure.
- Review the most recent system-test results for failed or incomplete gas-measurement items.
- If the machine recently froze or experienced an abnormal shutdown, perform a controlled restart and repeat the system test.
Do not interrupt power while the machine is supporting a patient.
Expected: The machine starts normally and either passes the gas-measurement portion of the system test or produces a repeatable failure.
If gas measurement returns and the complete test passes, perform a controlled functional verification before returning the unit to service.
4. Check the Sample-Line Connections
Inspect both ends of the sampling line.
Verify that the line is:
- Securely connected at the Y-piece, HME filter, patient-side filter, or approved hose adapter.
- Securely connected to the water trap.
- Routed without tension or sharp bends.
- Installed without unauthorized adapters.
- The correct compatible sampling line for the Perseus.
Drager directs that the sample line be securely connected at the patient-side sampling point and water trap, with no adapters used. An improperly connected or damaged line can cause faulty measurements.
Expected: The sample line is firmly connected and correctly routed.
If reseating the line restores stable CO2 and agent measurements, complete the system test and stop.
5. Inspect the Sample Line for Occlusion or Damage
Examine the full length of the sampling line for:
- Kinks or compression.
- Internal condensation.
- Fluid contamination.
- Cracks or loose fittings.
- Discoloration or residue.
- Damage caused by equipment movement.
Replace a questionable line with an approved new sample line rather than attempting to flush, clean, or disinfect it. Drager identifies sample lines as single-use items and warns that disinfectants can damage the sampling components.
Expected: A clean, dry, unobstructed sampling path is established.
If replacing the sample line restores the measurements, verify operation and stop.
6. Check the Patient-Side Filter or Sampling Port
Inspect the filter, HME, elbow, or adapter where the sample line connects.
Look for:
- Condensation blocking the sampling port.
- Secretions or contamination.
- A protective cap left installed.
- A damaged or incompatible filter.
- A loose sampling connection.
- An incorrect sampling location.
Replace a wet, blocked, contaminated, or questionable patient-side accessory with a compatible component.
The manufacturer’s remedies for sample-line disconnection or occlusion specifically include checking the sample line, water trap, and patient-side filter.
Expected: Gas can move freely from the patient connection through the sampling line.
If the values return after replacing the filter or HME, complete verification and stop.
7. Inspect the Water Trap
Check whether the water trap is:
- Full or overfilled.
- Contaminated.
- Cracked or physically damaged.
- Expired.
- Incorrectly seated in its holder.
- The correct compatible type.
- Missing its required membrane or internal components.
Empty or replace the water trap according to its instructions for use. Reseat it fully and confirm that any Water trap disconnected? or Water trap full alarm clears.
A full, damaged, contaminated, or improperly connected water trap can interrupt or distort gas measurement.
Do not apply silicone spray, aerosol cleaner, or lubricant to the water-trap holder or O-rings. Drager warns that silicone can disrupt measurement and silicone or aerosol residue may create a fire risk.
Expected: The water trap is clean, correctly seated, within its replacement interval, and free of excess fluid.
If replacement restores measurements, complete the system test and stop.
8. Distinguish Agent Measurement From Vaporizer Recognition
If CO2 measurement works but anesthetic-agent information is unavailable, determine whether the complaint involves:
- Actual inspiratory or expiratory agent concentration.
- Vaporizer type recognition.
- Vaporizer dial-position display.
- Vaporizer filling-level display.
- Agent-prediction information.
Inspect the vaporizer externally and confirm that it is:
- Correctly mounted and locked.
- Hanging vertically.
- Filled with the correct agent.
- Set to the intended concentration when testing is authorized.
- Free of obvious leakage or physical damage.
The optional Vapor View system provides vaporizer identification, dial-position, filling-level, and prediction information. A Vapor View failure is therefore different from a failure of the patient-gas measurement module.
Expected: The complaint is correctly classified as vaporizer recognition, agent delivery, or measured-agent concentration failure.
If the problem is limited to a persistent Vapor View hardware alarm, document it separately and escalate according to the displayed alarm guidance.
9. Perform the System Test
After correcting or replacing external sampling components:
- Configure the machine with an approved breathing circuit and test lung.
- Confirm the sample line and water trap are correctly installed.
- Keep the vaporizer off unless agent testing is specifically required and authorized.
- Run the complete Perseus system test.
- Review all gas-measurement results and alarms.
- Confirm that no gas-sensor, sampling-path, or water-trap alarm returns.
Drager warns that a device with nonoperational CO2 or anesthetic-agent sensors requires suitable substitute monitoring before clinical use.
Expected: The system test completes successfully without unresolved gas-measurement faults.
If the system test repeatedly reports a sensor failure, stop troubleshooting and escalate.
10. Perform a Controlled Measurement Verification
When authorized test equipment is available, verify gas-measurement performance using a certified gas source or analyzer test setup according to facility procedures.
Confirm:
- CO2 waveform and numerical values appear.
- Inspiratory and expiratory phases are detected.
- Anesthetic-agent type and concentration are detected when approved agent test gas is applied.
- Values remain stable.
- No sample-line, water-trap, accuracy, or gas-sensor alarm returns.
Do not use exhaled breath, improvised chemicals, or uncontrolled anesthetic-agent delivery as a test source.
The manufacturer’s safety-check specifications use certified test-gas concentrations to verify CO2 and anesthetic-agent accuracy and also require sampling-flow and leakage evaluation of the patient-gas measurement module.
Expected: Gas values are present, stable, and reasonable for the approved test source.
If verification passes and all required safety testing is complete, return the machine to service according to facility policy.
If the Problem Persists
If the sample line, patient-side filter, water trap, vaporizer condition, power state, and system-test setup have been checked, common external causes have been ruled out.
A persistent Gas sensor failure, repeated CO2 sensor accuracy low, failed system-test result, or inability to detect approved test gas suggests a fault involving the internal patient-gas measurement module or internal sampling pathway.
The device should be:
- Removed from service.
- Labeled Out of Service.
- Sent for qualified bench evaluation or Drager service.
- Preserved with the exact alarms, system-test results, and replaced accessories documented.
Do not open the gas-measurement module or attempt board-level repair without appropriate authorization, training, documentation, and test equipment.
Knowing when external troubleshooting is complete and escalation is required is proper troubleshooting.
Clinical Use Tip
Never troubleshoot missing CO2 or anesthetic-agent monitoring while relying on the affected machine for an active patient.
Move the patient to another verified anesthesia machine or establish approved independent gas monitoring before continuing. Anesthesia delivery without dependable ventilation and agent monitoring presents a serious patient-safety risk.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"OR staff reported that the Perseus displayed no CO2 waveform or sevoflurane concentration during pre-use setup."
Cause
What was observed during troubleshooting.
Example:
"The water trap was full and the sample line contained condensate, preventing the patient-gas measurement module from obtaining a sample."
Resolution
What action was taken.
Example:
"Replaced the water trap and sample line, completed the system test, verified CO2 and anesthetic-agent measurement with an approved test setup, and returned the machine to service."
Helpful Details to Include (If Known)
- Exact alarm text and priority
- Whether CO2, agent, O2, or all gas values were unavailable
- Whether the problem occurred during startup or patient use
- System-test results
- AC-power and startup status
- Sample-line condition
- Sample line replaced
- Patient-side filter or HME replaced
- Water-trap level and condition
- Water trap replaced or reseated
- Vaporizer type and position
- Vapor View alarms present
- Approved gas-test results
- Unusual sounds, heat, odor, or contamination
- Final device status
- Removed from service or returned to service
Final Thought
Unavailable gas measurements require a safety-first response and a logical inspection of the complete sampling path. Checking connections, consumables, moisture, test results, and vaporizer conditions can resolve many external problems without unnecessary disassembly. Persistent sensor failures require removal from service, qualified repair, and complete CCR documentation.
That is successful troubleshooting.