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What This Guide Helps With
Troubleshooting low, high, or inconsistent delivered tidal volume caused by settings, circuit leaks, restrictions, sensors, breathing-system components, or ventilation-mode selection.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended ventilator troubleshooting while the Aisys CS2 is supporting an active patient.
If delivered tidal volume is significantly different from the intended value during clinical use:
- Notify the anesthesia provider immediately.
- Confirm ventilation using chest movement, airway pressure, capnography, oxygen saturation, and an independent measurement when available.
- Provide ventilation using another verified anesthesia machine or an approved backup method.
- Maintain appropriate independent patient monitoring.
- Follow the facility’s anesthesia-equipment failure procedure.
Expected outcome: Patient care no longer depends on equipment with uncertain volume delivery.
Continue troubleshooting only after the machine has been removed from active patient use.
2. Confirm the Reported Volume Problem
Record:
- Selected ventilation mode
- Set tidal volume
- Inspired and expired tidal-volume measurements
- Respiratory rate
- Peak airway pressure
- PEEP
- Fresh-gas flow
- Any displayed alarms or advisory messages
- Whether the problem occurs continuously or intermittently
Determine whether the displayed volume is consistently low, consistently high, unstable, or only abnormal in a specific mode.
Expected outcome: The failure is clearly defined and can be reproduced under controlled conditions.
3. Verify the Selected Ventilation Mode
Confirm whether the machine is operating in a volume-targeted or pressure-targeted mode.
In pressure-controlled ventilation, the delivered tidal volume varies with the selected inspiratory pressure, lung compliance, airway resistance, PEEP, and patient effort. A specific tidal volume is not directly guaranteed.
Select the facility-approved test configuration and verify the intended mode and settings.
Expected outcome: The reported difference is not simply the expected behavior of a pressure-targeted ventilation mode.
If correcting the mode or settings restores the expected volume, complete the checkout and return the device to service.
4. Confirm That Setting Changes Were Accepted
Verify that the tidal-volume setting was entered and confirmed using the touchscreen or ComWheel.
Check for:
- An unconfirmed highlighted value
- An unintended ventilation mode
- Incorrect respiratory rate or inspiratory time
- Incorrect pressure limit
- Incorrect PEEP
- An inappropriate patient weight or ventilation setup
GE Healthcare identifies tidal volume as one of the adjustable ventilator parameters available through the Aisys CS2 controls.
Expected outcome: The active ventilator settings match the intended test values.
5. Inspect the Breathing Circuit and Test Lung
Use a known-good, compatible breathing circuit and test lung.
Inspect the complete circuit for:
- Loose or partially connected fittings
- Split, stretched, or punctured tubing
- Open sampling or accessory ports
- Loose filter, elbow, mask, or test-lung connection
- Incorrectly installed water traps
- Excessive circuit moisture
- Kinked or compressed tubing
- Restricted filters or accessories
Remove unnecessary accessories and repeat the test with the simplest approved circuit configuration.
Expected outcome: A secure, unobstructed circuit produces a stable measured tidal volume.
If replacing or reconnecting the circuit resolves the problem, stop troubleshooting and document the defective component.
6. Perform the Approved Machine Checkout and Leak Test
Run the Aisys CS2 preoperative checkout or system leak test according to the facility procedure and current GE Healthcare instructions.
Do not bypass a failed checkout.
A leak may prevent the full delivered volume from reaching the test lung and can cause a difference between inspired and expired volume measurements.
Expected outcome: The machine passes the complete checkout without breathing-system, circuit, flow-sensor, or ventilator errors.
If the checkout fails, correct only accessible setup problems identified by the test and repeat it.
7. Check the Bag/Ventilator Switch and Bellows Assembly
Confirm that the Bag/Ventilator switch is fully positioned in ventilator mode.
Inspect the bellows and bellows housing externally for:
- Bellows not rising normally
- Bellows collapsing before the breath is complete
- Uneven or delayed bellows movement
- A displaced bellows assembly
- Visible damage
- Improperly seated breathing-system components
Do not disassemble internal ventilator components during basic troubleshooting.
Expected outcome: The bellows fills and cycles consistently with each mechanical breath.
Abnormal bellows movement combined with low delivered volume may indicate a breathing-system leak, drive-gas problem, valve problem, or internal ventilator fault.
8. Inspect the Flow Sensors
Remove the machine from use before handling the flow sensors.
Check the inspiratory and expiratory flow sensors for:
- Incorrect installation
- Loose electrical or pneumatic connections
- Moisture or condensation
- Visible contamination
- Cracks or physical damage
- Reversed or mismatched placement
Allow wet components to dry or replace them with known-good compatible components according to facility policy. Run the required calibration or checkout afterward.
Expected outcome: Flow-sensor calibration passes and inspired and expired volume measurements become stable and reasonable.
Do not clean flow sensors using an unapproved method.
9. Compare Inspired and Expired Tidal Volume
Using a known-good test lung, compare:
- Set tidal volume
- Inspired tidal volume
- Expired tidal volume
- Bellows movement
- Independent analyzer measurement, when available
Interpret the pattern:
- Set and inspired volume agree, but expired volume is low: Check for circuit leakage, test-lung leakage, sampling losses, or expiratory measurement problems.
- Both inspired and expired volumes are low: Check mode, pressure limitation, circuit restriction, bellows operation, flow sensors, gas supply, and ventilator performance.
- Displayed measurements disagree with an external analyzer: Suspect flow-sensor calibration, sensor contamination, configuration, or measurement-system failure.
- Volume varies as airway pressure rises: Check for restriction, pressure limiting, test-lung compliance, and inappropriate ventilator settings.
Expected outcome: The test identifies whether the problem involves actual volume delivery or inaccurate volume measurement.
10. Check for Airway-Pressure Limitation or Restriction
Observe peak airway pressure during the test.
Inspect for:
- A low pressure-limit setting
- Occluded or kinked tubing
- Saturated or restricted filters
- Blocked expiratory components
- Excessive PEEP
- Restricted absorber or breathing-system components
- A stiff or incorrectly configured test lung
The ventilator may be unable to deliver the complete set volume when the pressure limit is reached.
Expected outcome: The full set volume is delivered without reaching the configured pressure limit.
If removing a restriction restores normal delivery, replace the affected accessory and repeat the checkout.
11. Verify Pipeline Gas Supply
Confirm that the oxygen and air pipeline hoses are fully connected and that supply-pressure indicators are within the facility’s acceptable range.
Check for:
- Closed zone valves
- Loose pipeline connections
- Damaged hoses
- Incorrect gas connection
- Active supply-pressure alarms
- Failure occurring only on one gas source
Do not rely solely on cylinder pressure when evaluating normal pipeline operation.
Expected outcome: Stable gas supplies are available and no gas-supply alarms are present.
12. Test With Known-Good External Components
When compatible replacements are available, substitute one component at a time:
- Breathing circuit
- Filter
- Test lung
- Flow sensors
- Sampling line and water trap
- Removable breathing-system assembly
Repeat the checkout after each change.
Expected outcome: The defective external component is isolated without unnecessary internal disassembly.
If a substitution resolves the problem, remove the failed component from service and document the finding.
13. Verify Performance With a Calibrated Analyzer
Connect a calibrated ventilator or anesthesia-system analyzer using the facility-approved test setup.
Verify, as applicable:
- Delivered tidal volume
- Respiratory rate
- Inspiratory time
- Airway pressure
- PEEP
- Minute volume
- Oxygen concentration
- Alarm operation
Test representative ventilation settings within the device’s intended clinical range. GE Healthcare describes the Aisys CS2 as an anesthesia delivery system with integrated advanced ventilation and respiratory monitoring.
Expected outcome: Measured performance falls within the manufacturer’s applicable specifications and facility acceptance criteria.
Do not return the machine to service based only on the internal display when volume accuracy was the original complaint.
If the Problem Persists
If settings, ventilation mode, circuit integrity, accessories, flow sensors, gas supplies, bellows operation, checkout results, and external analyzer measurements have been evaluated, common external causes have been ruled out.
The problem may involve an internal ventilator valve, drive-gas system, flow-measurement circuit, breathing-system component, or electronic control failure.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for authorized repair or bench evaluation
- Evaluated using the current GE Healthcare technical documentation by qualified service personnel
Do not continue repeated clinical testing or begin unauthorized internal disassembly. Knowing when to stop and escalate is proper troubleshooting.
Clinical Use Tip
Never verify questionable tidal-volume delivery on an active patient. Move the patient to another verified ventilation method first, then test the machine with an approved circuit, test lung, and calibrated analyzer.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Anesthesia staff reported that the Aisys CS2 delivered approximately 350 mL when the ventilator was set for a 500 mL tidal volume."
Cause
What was observed during troubleshooting.
Example:
"Inspection found a loose connection between the expiratory circuit limb and the breathing-system outlet, causing a significant circuit leak."
Resolution
What action was taken.
Example:
"Reseated the circuit connection, replaced the stretched breathing hose, completed the machine checkout, and verified tidal volume with a calibrated analyzer; device passed and was returned to service."
Helpful Details to Include (If Known)
- Patient removed from the device before troubleshooting
- Ventilation mode and complete settings
- Set, inspired, and expired tidal volumes
- Peak pressure and PEEP
- Exact alarm or advisory message
- Pipeline gas pressures verified
- Breathing circuit and accessories inspected
- Circuit or test lung substituted
- Leak-test result
- Flow-sensor condition and calibration result
- Bellows behavior
- Analyzer manufacturer, model, and calibration status
- Measured tidal volumes at each tested setting
- Unusual sounds, heat, odor, or vibration
- Final device status
Final Thought
Reliable tidal-volume troubleshooting requires distinguishing between incorrect settings, expected mode behavior, circuit losses, measurement errors, and an actual ventilator failure. Protect the patient first, verify performance objectively, escalate internal faults appropriately, and clearly document the evidence supporting the final device status.
That is successful troubleshooting.