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What This Guide Helps With
Delivered tidal volume differing from the set value because of circuit leaks, compliance, obstruction, sensor issues, settings, or gas-delivery problems.
Step-by-Step Troubleshooting
1. Protect the Patient and Establish Alternate Ventilation
If inadequate ventilation is suspected during a case, immediately ensure ventilation through another verified method or anesthesia machine. Do not continue troubleshooting while the patient depends on unreliable tidal-volume delivery.
Expected outcome: Adequate patient ventilation is independently maintained.
2. Confirm the Reported Volume Problem
Using an appropriate test lung and approved test equipment when necessary, confirm the discrepancy between the selected ventilation settings and the observed or measured delivered volume.
Record ventilation mode, relevant settings, displayed inspired and expired volumes, and whether the discrepancy is repeatable.
Expected outcome: The tidal-volume discrepancy is confirmed under controlled conditions.
3. Inspect the Patient Circuit for Leaks or Disconnections
Check all circuit limbs, connectors, Y-piece, reservoir bag, filters, adapters, and sampling connections. Look for loose fittings, cracks, open ports, or partially disconnected components.
Circuit leakage may reduce measured or delivered volume without an internal ventilator failure.
Expected outcome: The circuit is intact and leak-free. If correcting the leak restores expected volume delivery, troubleshooting can stop after verification.
4. Check for External Obstruction or Excessive Resistance
Inspect the patient circuit, filters, adapters, and externally accessible breathing-system components for kinks, occlusions, water accumulation, collapsed tubing, or improperly installed accessories.
Expected outcome: Gas flow through the external breathing path is unobstructed.
5. Verify Ventilation Settings and Controls
Confirm the intended ventilation mode and settings are actually selected. Review relevant pressure, flow, volume, timing, and limit settings without changing configuration outside normal clinical controls.
Ensure the reported discrepancy is not the expected result of the selected ventilation mode or test setup.
Expected outcome: The machine is configured as intended for the test being performed.
6. Verify Flow-Sensing Components
Inspect externally accessible flow sensors and associated removable components for correct installation, contamination, moisture, damage, or poor seating.
If calibration is available through normal approved procedures, verify that calibration completes successfully.
Expected outcome: Flow measurement components are correctly installed and functioning without calibration errors.
7. Use a Known-Good Circuit and Test Lung
When appropriate, substitute a known-good compatible breathing circuit and test lung to distinguish machine performance from circuit or accessory problems.
Expected outcome: Delivered and measured ventilation returns to expected behavior with known-good accessories, identifying the external component as the cause.
8. Verify Gas Supply and System Test Status
Confirm required gas supplies are connected and available and that the machine can complete its normal system test without relevant failures.
Expected outcome: Adequate gas supply and normal system-test status are confirmed.
9. Perform Final Ventilation Verification
Run the ventilator on an appropriate test lung through the relevant operating mode and confirm stable volume delivery, pressure behavior, displayed measurements, and alarm response.
Expected outcome: Ventilator performance is stable and consistent with the selected settings. If so, troubleshooting can stop.
10. Escalate Unresolved Volume Delivery Problems
If significant volume discrepancy continues after circuit, obstruction, settings, sensing, accessories, and gas supply have been verified, remove the machine from service.
Expected outcome: Further investigation is transferred to qualified service personnel.
If the Problem Persists
Common external causes have been ruled out. The remaining problem may involve an internal ventilator, pneumatic, flow-measurement, pressure-measurement, valve-control, or configuration issue.
Remove the machine from service, label it Out of Service, and perform further bench evaluation using appropriate Drager documentation and approved anesthesia-machine test equipment. Internal repairs or service-level calibration should be completed only by qualified personnel.
After repair, verify ventilation performance, system tests, relevant alarms, and measurement accuracy before clinical use.
Knowing when to stop external troubleshooting and escalate is proper troubleshooting.
Clinical Use Tip
When delivered tidal volume is questionable, rely on an alternate verified means of ventilation rather than continuing a case on uncertain ventilator performance.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"OR staff reported the Atlan A300 was displaying substantially less tidal volume than the selected setting."
Cause
What was observed during troubleshooting.
Example:
"Clinical Engineering found a loose connection at the patient-circuit Y-piece causing a significant breathing-circuit leak."
Resolution
What action was taken.
Example:
"Secured the circuit connection, completed the system test, verified stable ventilation and volume measurements with a test lung, and returned the machine to service."
Helpful Details to Include (If Known)
- Ventilation mode
- Selected tidal volume or relevant settings
- Displayed inspired and expired volumes
- Circuit condition
- Filters and adapters used
- Leak-test result
- Flow-sensor status
- Gas-supply status
- Known-good circuit or test-lung results
- Results before and after correction
- Final functional status
Final Thought
Confirm inadequate ventilation objectively, rule out circuit and setup problems first, verify sensing and gas supply, and escalate rather than accepting uncertain ventilator performance.
That is successful troubleshooting.