On this page
Asset Type
Manufacturer
Model
What This Guide Helps With
Troubleshooting drifting gas measurements, unstable readings, or calibration-related issues before sending the monitor for repair.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not troubleshoot a suspected measurement accuracy issue on an active patient unless safe alternate monitoring is already in place.
Action:
- Remove the Vamos 2 from active anesthesia use if readings are drifting, unstable, or not clinically believable.
- Confirm the patient is being monitored by another verified gas analyzer or anesthesia monitor if monitoring is still required.
- Notify anesthesia staff that the device should not be trusted until verified.
Expected outcome: Patient safety is protected before troubleshooting begins.
Why it matters: A drifting anesthesia gas or CO₂ measurement can affect ventilation assessment, agent delivery awareness, and clinical decision-making.
If this resolves the immediate safety concern, continue troubleshooting off-patient.
2. Verify the Reported Measurement Problem
Confirm exactly what is drifting or failing calibration.
Action:
- Ask staff what parameter was affected, such as end-tidal CO₂, inspired CO₂, O₂, N₂O, anesthetic agent concentration, or agent identification.
- Observe whether the reading is slowly drifting upward or downward.
- Check whether the reading is intermittently unstable.
- Check whether the reading is flatlined.
- Compare whether the reading is different from another monitor.
- Confirm whether the device is failing a calibration or zeroing process.
Expected outcome: The reported issue is clearly identified before parts or accessories are changed.
Why it matters: “Calibration issue” can be caused by the monitor, sampling line, water trap, gas source, contamination, or incorrect setup.
3. Check for Active Alarms or Status Messages
Look for occlusion, sampling, calibration, zeroing, or gas measurement messages.
Action:
- Review the Vamos 2 display for any active messages related to sample line occlusion.
- Check for water trap issue messages.
- Check for calibration needed messages.
- Check for zeroing failure messages.
- Check for gas measurement unavailable messages.
- Check for agent identification failure messages.
- Check for pump or flow issue messages.
Expected outcome: Any displayed alarm helps narrow the cause.
If the monitor shows a sampling system or occlusion alarm, troubleshoot the sampling path before assuming calibration failure.
4. Inspect the Sampling Line
Check the sample line from the patient connection to the Vamos 2.
Action:
- Look for kinks.
- Look for moisture.
- Look for secretions.
- Look for crushed tubing.
- Look for loose luer connections.
- Check for incorrect sample line type.
- Check for a blocked filter or connector.
- Replace the sample line with a known-good compatible line.
Expected outcome: Gas readings stabilize after replacing a restricted or contaminated sample line.
Why it matters: Partial restriction or contamination can cause delayed response, incorrect values, or drifting measurements.
If readings stabilize, document the faulty sample line and return the monitor to service after verification.
5. Check the Water Trap
Inspect the water trap for fluid, contamination, improper seating, or age-related issues.
Action:
- Remove and inspect the water trap.
- Empty or replace it according to facility procedure.
- Confirm it is fully seated and locked into place.
- Check for cracks, missing seals, or visible contamination.
Expected outcome: The monitor samples normally and measurements become stable.
Why it matters: A leaking or saturated water trap can affect sample flow and measurement accuracy.
If the issue clears after replacing or reseating the water trap, stop and document the accessory-related cause.
6. Allow Proper Warm-Up Time
Confirm the monitor has had enough time to stabilize after power-up.
Action:
- Power the monitor on.
- Allow it to complete startup and warm-up.
- Do not judge gas accuracy immediately after power-on unless the device indicates it is ready.
Expected outcome: Readings become stable after normal warm-up.
Why it matters: Gas analyzers may require stabilization time before accurate measurement is available.
If the drift disappears after warm-up, document that no fault was duplicated after stabilization.
7. Verify the Sample Gas Source
If bench testing, use a known-good gas source or simulator appropriate for the parameter being checked.
Action:
- Use a verified test gas or approved analyzer test setup if available.
- Confirm the gas cylinder is not expired, empty, mislabeled, or connected incorrectly.
- Compare readings only against a known-good reference.
Expected outcome: The Vamos 2 reading matches the expected gas value within acceptable facility or manufacturer tolerance.
Why it matters: A bad test source can make a good monitor appear out of calibration.
8. Compare Against Another Known-Good Monitor
Use a second verified analyzer when possible.
Action:
- Connect both monitors to the same appropriate test source or controlled sampling setup.
- Allow both devices to stabilize.
- Compare the readings.
Expected outcome: The Vamos 2 either agrees with the reference monitor or shows a repeatable offset/drift.
Why it matters: Comparison testing helps separate a true device issue from a setup or gas source issue.
If the Vamos 2 agrees with the reference monitor, document no fault found and include the test conditions.
9. Check for Leaks in the Sampling Path
A small leak can dilute the sampled gas and cause low, unstable, or drifting values.
Action:
- Inspect all external fittings and sample connections.
- Confirm the water trap is properly installed.
- Check for loose adapters or damaged sample line connectors.
- Replace questionable external accessories.
Expected outcome: Readings stabilize when the sampling path is sealed.
Why it matters: Leaks can mimic calibration drift by allowing room air into the gas sample.
10. Check for Contamination or Residual Moisture
Moisture, residue, or contaminated accessories can cause slow response and measurement instability.
Action:
- Replace the sample line and water trap.
- Allow the monitor to sample clean room air or approved test gas.
- Observe whether readings return to expected baseline behavior.
Expected outcome: The analyzer clears and readings stabilize.
Why it matters: Contamination in the sampling path can cause false drift even when the internal analyzer is functioning.
11. Perform User-Level Zeroing or Calibration Check Only if Allowed
Use only facility-approved and manufacturer-supported procedures available to Clinical Engineering.
Action:
- Follow the hospital-approved procedure for any external zeroing, calibration check, or verification.
- Do not perform unauthorized internal calibration adjustments.
- Record the starting value, expected value, final value, and result.
Expected outcome: The device passes verification or clearly fails in a repeatable way.
Why it matters: Clinical Engineering should verify performance without creating an undocumented or unauthorized calibration change.
12. Power Cycle and Recheck
If the issue is intermittent, power cycle the monitor and retest.
Action:
- Turn the monitor off.
- Disconnect from patient use and external accessories.
- Reconnect known-good sampling accessories.
- Power the unit back on.
- Allow warm-up and repeat the measurement check.
Expected outcome: The issue either clears or returns consistently.
Why it matters: A repeatable failure is stronger evidence of an internal measurement or calibration problem.
13. Determine Whether the Device Can Be Returned to Service
Only return the monitor to service if the readings are stable and verified.
Action:
- Confirm no active gas measurement alarms remain.
- Confirm the sampling system operates normally.
- Confirm readings are stable.
- Confirm external accessories have been replaced or verified.
- Confirm the device passes the facility’s performance check.
Expected outcome: The monitor is safe to return to clinical use.
If measurement drift remains, do not return the device to service.
If the Problem Persists
If the Vamos 2 continues to show measurement drift, unstable gas values, failed zeroing, or failed calibration verification after external causes are ruled out, the issue is likely internal.
Remove the device from service.
Label it Out of Service.
Send it for repair, bench evaluation, or vendor/service-level calibration.
Common external causes such as sample line restriction, water trap issues, leaks, contamination, warm-up time, and bad test gas should be ruled out first. Knowing when to stop is proper troubleshooting.
Clinical Use Tip
Do not troubleshoot questionable gas measurements during an active case unless patient safety is protected first. Move monitoring to a known-good device before testing, replacing accessories, or performing verification checks.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Anesthesia reported the Drager Vamos 2 gas readings were drifting and did not match expected CO₂ and agent values during use."
Cause
What was observed during troubleshooting.
Example:
"Inspection found a contaminated water trap and moisture in the sampling line causing unstable gas measurement readings."
Resolution
What action was taken.
Example:
"Replaced the water trap and sample line, allowed the monitor to warm up, verified stable readings with a known-good test setup, and returned the device to service."
Helpful Details to Include (If Known)
- Alarm behavior, including occlusion, calibration, zeroing, or gas measurement messages noted
- Accessories swapped, including sampling line, water trap, filter, or connectors
- Power behavior, including outlet tested, power cord condition checked, startup behavior, and warm-up time allowed
- Environmental factors, including moisture, contamination, visible residue, or unusual pump noise
- Indicator lights or displayed status messages observed during testing
- Final device status, including whether readings were verified, no fault was found, returned to service, or removed from service
Final Thought
Measurement drift should be treated as a patient safety concern until proven otherwise. Start with the sampling path, water trap, leaks, accessories, warm-up, and test setup before suspecting internal analyzer failure. If readings cannot be verified, remove the monitor from service and document the complaint, cause, and resolution clearly.
That is successful troubleshooting.