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What This Guide Helps With
Addresses flow-sensor calibration failures caused by contamination, moisture, improper installation, connection problems, leaks, or defective external sensor components.
Step-by-Step Troubleshooting
1. Protect the Patient and Remove the Machine From Active Use
Do not troubleshoot unreliable inspiratory or expiratory flow measurement while a patient depends on the machine. Move the patient to another verified anesthesia system.
Expected outcome: The patient is supported independently and the machine can be evaluated without clinical risk.
2. Confirm Which Sensor or Test Is Failing
Repeat the normal system test in a controlled setup and document whether the inspiratory sensor, expiratory sensor, or both fail calibration.
Record the displayed message exactly.
Expected outcome: The affected measurement channel is identified. If calibration now succeeds, perform final verification before return to service.
3. Inspect Sensor Installation
Verify each accessible flow sensor is installed in the correct position and orientation and is fully seated.
Check for a sensor that was recently removed for cleaning and reinstalled incorrectly.
Expected outcome: Sensors are installed correctly and securely. If reseating resolves the calibration failure, continue to final verification.
4. Inspect for Moisture or Contamination
Remove the affected external sensor according to approved handling procedures and inspect for moisture, condensation, residue, debris, or visible damage.
Allow components intended to be dry to become fully dry before retesting. Do not use unapproved cleaning methods.
Expected outcome: The sensor pathway is clean, dry, and unobstructed.
5. Inspect Sensor Connections
Check accessible sensor electrical connections, contacts, and mounting interfaces for contamination, looseness, bent features, or incomplete engagement.
Do not probe or alter internal electronics.
Expected outcome: The sensor connection is clean and secure with no visible damage.
6. Check the Breathing System for Leaks or Incorrect Assembly
Verify the breathing system, circuit, absorber, and related components are correctly installed and pass basic external inspection.
A significant leak or incorrect assembly may interfere with calibration or test conditions.
Expected outcome: The breathing system is correctly assembled with no obvious external leak.
7. Substitute a Known-Good Compatible Sensor
If available and permitted by facility procedure, replace the suspect sensor with a known-good compatible sensor.
Repeat the normal calibration or system test.
Expected outcome: If calibration passes with the known-good sensor, the original sensor is identified as defective and should be removed from service.
8. Restart and Repeat Calibration
Perform a normal restart and rerun the standard system test after external corrections.
Do not enter restricted service calibration procedures.
Expected outcome: Both inspiratory and expiratory flow sensors calibrate successfully. If so, troubleshooting can stop after functional verification.
9. Verify Flow and Volume Measurements
Use an approved anesthesia/ventilator analyzer and test lung to verify that displayed flow and volume values respond appropriately during controlled ventilation.
Confirm alarms and general ventilation function.
Expected outcome: Flow measurements are stable and credible and the system passes required functional tests.
10. Escalate Persistent Calibration Failure
If sensor installation, cleanliness, connections, breathing-system setup, and known-good substitution do not resolve the failure, remove the machine from service.
Expected outcome: The problem is referred for service-level evaluation of sensor interfaces, internal pneumatic pathways, or associated electronics.
If the Problem Persists
Common external causes such as moisture, contamination, incorrect sensor installation, loose connections, leakage, and defective replaceable sensors have been ruled out. The remaining problem may involve the sensor interface, internal flow path, signal processing, 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 Drager service documentation and approved flow-analysis equipment.
- Repaired or calibrated only by qualified personnel.
- Fully verified for flow, volume, ventilation, alarms, and system-test performance before return to service.
Stopping before unauthorized internal calibration or repair is proper troubleshooting.
Clinical Use Tip
Do not rely on ventilation measurements from a machine that cannot successfully calibrate its flow sensors.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"OR staff reported that the Drager Atlan A100 repeatedly failed expiratory flow-sensor calibration during the system test."
Cause
What was observed during troubleshooting.
Example:
"Clinical Engineering found condensation on the expiratory flow sensor following breathing-system cleaning."
Resolution
What action was taken.
Example:
"Clinical Engineering removed and dried the sensor according to approved handling practices, reinstalled it correctly, completed calibration and the system test successfully, verified ventilation measurements, and returned the machine to service."
Helpful Details to Include (If Known)
- Sensor identified by the test
- Exact displayed calibration message
- Sensor orientation and seating
- Moisture or contamination found
- Connection condition
- Breathing-system leak status
- Known-good sensor substitution
- Analyzer comparison
- Final calibration result
- Final device status
Final Thought
Flow-sensor calibration failures should be approached from the outside in. Verify installation, cleanliness, connections, leaks, and known-good components before assuming an internal fault, then document and escalate appropriately when calibration remains unsuccessful.
That is successful troubleshooting.