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What This Guide Helps With
Helps isolate external circuit, leak, sensor, setting, compliance, or test-setup causes when displayed or delivered tidal volume appears low, unstable, or inaccurate.
Step-by-Step Troubleshooting
1. Protect the Patient and Maintain Ventilation
Do not troubleshoot unreliable tidal-volume delivery or monitoring while a patient depends on the affected anesthesia machine. Provide an alternate verified ventilation method or anesthesia machine as clinically appropriate.
Expected outcome: Patient ventilation is maintained independently and the Fabius can be evaluated safely.
2. Confirm Whether the Problem Is Delivery, Measurement, or Both
Determine whether clinical staff observed low measured tidal volume, visibly poor chest excursion, unstable displayed values, a discrepancy with another monitor, or an actual inability to deliver the expected volume.
Reproduce the concern on an appropriate test lung rather than on a patient.
Expected outcome: The complaint is categorized as a delivery problem, measurement problem, or combined issue.
3. Verify Ventilation Settings and Mode
Confirm the selected ventilation mode and externally adjustable settings match the intended test conditions. Check for an unintended change in set volume, rate, pressure, PEEP, or other clinically accessible parameters relevant to the selected mode.
Do not alter restricted service configuration.
Expected outcome: The machine is configured as intended. If correcting an erroneous setting resolves the discrepancy, proceed to final verification.
4. Inspect the Patient Circuit for Leaks or Misconnection
Inspect circuit limbs, patient Y-piece, bag, filters, adapters, sampling connections, and breathing-system fittings for leaks, disconnections, or incorrect assembly.
Expected outcome: The breathing circuit is intact and properly connected. If correction restores stable tidal volume, troubleshooting can stop after verification.
5. Evaluate Circuit Compliance and External Accessories
Check whether additional tubing, filters, humidification components, adapters, or test accessories were added when the problem began. Compare the setup with a known-good standard configuration when practical.
Expected outcome: No external accessory or unusual circuit configuration is causing an apparent or actual reduction in delivered volume.
6. Inspect the Flow-Measurement Path
Inspect externally accessible flow-sensor components, connections, and associated tubing or cables when applicable. Look for contamination, moisture, incorrect orientation, loose seating, or damaged connectors.
Do not clean or service sensors using unapproved methods.
Expected outcome: The flow-measurement path is correctly installed and free of obvious external problems. If reseating or an approved known-good substitution corrects the reading, proceed to final verification.
7. Compare Displayed Volume With Approved Test Equipment
Using an appropriate anesthesia analyzer or ventilator test device, compare delivered volume under controlled bench conditions.
Do not conclude the internal measurement system has failed solely from visual observation.
Expected outcome: Delivered and indicated performance is reasonably consistent with the applicable manufacturer test procedure. If the machine performs correctly, investigate external clinical setup factors before condemning the unit.
8. Check for Pressure Limitation or Flow Restriction
Inspect the circuit for kinks, occluded filters, blocked tubing, restricted valves or accessories, and other external conditions that could prevent expected delivery.
Expected outcome: The gas pathway is unrestricted. If removal of an external restriction restores volume, troubleshooting can stop after verification.
9. Perform Final Functional Verification
After correction, verify stable ventilation on a test lung across the applicable operating condition and confirm volume display, alarms, pressure response, and breathing-system integrity.
Expected outcome: Tidal volume remains stable and consistent with approved testing. If so, the device may be returned to service after required checks.
10. Escalate Persistent Volume Error
If measured or delivered tidal volume remains abnormal after settings, circuit integrity, accessories, restrictions, and external sensing components have been ruled out, remove the unit from service.
Expected outcome: Further evaluation is performed under approved service procedures rather than continued external troubleshooting.
If the Problem Persists
Common external causes have been ruled out. Remaining categories may include internal ventilator pneumatic performance, flow measurement, pressure regulation, calibration, internal leakage, or other service-level faults.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for repair or bench evaluation
- Evaluated using appropriate manufacturer documentation and approved test equipment
- Repaired or calibrated only by qualified personnel
Complete applicable ventilator-performance, alarm, breathing-system, and electrical-safety testing before return to service.
Clinical Use Tip
A normal displayed tidal volume does not prove adequate patient ventilation; verify actual ventilation clinically and use an alternate device whenever delivery is in doubt.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Anesthesia staff reported unstable and lower-than-expected tidal-volume readings during machine setup."
Cause
What was observed during troubleshooting.
Example:
"Clinical Engineering found a loose expiratory circuit connection causing leakage and unstable measured volume."
Resolution
What action was taken.
Example:
"The connection was corrected, the circuit passed leak testing, and tidal-volume delivery was verified with approved test equipment."
Helpful Details to Include (If Known)
- Ventilation mode
- Set and observed volume
- Test-lung results
- Circuit configuration
- Filters or adapters installed
- Leak-test result
- Flow-sensor condition
- Known-good substitutions
- Analyzer readings
- Final functional status
- Ventilation mode
- Set and observed volume
- Test-lung results
- Circuit configuration
- Filters or adapters installed
- Leak-test result
- Flow-sensor condition
- Known-good substitutions
- Analyzer readings
- Final functional status
Final Thought
Begin with safe alternate ventilation, then distinguish a true delivery problem from a measurement problem. Check settings, circuits, accessories, and sensing components before suspecting internal ventilator failure, and document objective test results before return to service.
That is successful troubleshooting.