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What This Guide Helps With
Troubleshooting elevated PEEP or incomplete exhalation caused by settings, circuit restrictions, valves, moisture, accessories, scavenging, or breathing-system installation problems.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended troubleshooting while the Aisys CS2 is supporting an active patient.
If expiratory pressure remains elevated during a procedure:
- Notify the anesthesia provider immediately.
- Confirm ventilation, oxygenation, airway pressure, and patient monitoring.
- Move ventilation to another verified anesthesia machine or approved backup method when pressure cannot be controlled.
- Follow the facility’s anesthesia-equipment failure procedure.
Expected outcome: Patient ventilation no longer depends on equipment with unresolved elevated expiratory pressure.
Continue troubleshooting only after the machine is removed from active patient use.
2. Confirm the Reported Condition
Review the alarm history and determine whether the issue involves:
- PEEP above the selected value.
- Airway pressure failing to return to baseline.
- Continuous positive pressure between breaths.
- Slow or incomplete exhalation.
- Bellows failing to refill normally.
- Elevated pressure occurring only in a specific ventilation mode.
- Elevated pressure during manual ventilation only.
Record the displayed pressure values, selected PEEP, ventilation mode, and complete alarm message.
Expected outcome: The failure condition is clearly identified and can be reproduced safely.
If the condition cannot be reproduced and the machine passes a complete checkout, document the findings and follow facility policy before returning it to service.
3. Verify the Selected PEEP and Ventilation Settings
Confirm that:
- The selected PEEP matches the intended clinical setting.
- Respiratory rate and inspiratory time allow sufficient time for exhalation.
- The inspiratory-to-expiratory ratio is appropriate.
- Tidal volume or inspiratory pressure is not producing an unintended pressure condition.
- Any ventilation-mode changes were entered correctly.
The Aisys CS2 provides adjustable PEEP during mechanical ventilation, so an incorrect setting can appear similar to a mechanical expiratory restriction.
Return the settings to a known test configuration using an appropriate test lung.
Expected outcome: Expiratory pressure returns to the selected baseline.
If the pressure normalizes, the issue was setting-related. Verify operation, document the correction, and stop.
4. Inspect the Patient Breathing Circuit
Disconnect and inspect the complete breathing circuit for:
- Kinked or compressed tubing.
- Internally collapsed tubing.
- Water accumulation.
- Blocked filters or heat-and-moisture exchangers.
- Incorrectly installed adapters.
- Obstructed elbows, connectors, or sampling components.
- Excessively long or nonapproved circuit configurations.
Replace questionable disposable components with known-good compatible components.
Expected outcome: Gas moves freely through the inspiratory and expiratory limbs without restriction.
If replacing the circuit resolves the elevated pressure, complete a checkout, document the defective component, and stop.
5. Check the Expiratory Limb and Accessories
Pay particular attention to components affecting exhalation:
- Expiratory breathing hose.
- Expiratory bacterial filter.
- Water traps.
- Nebulizer adapters.
- Gas-sampling connections.
- Test lungs or breathing bags used during evaluation.
Temporarily remove unnecessary accessories and test with a basic known-good circuit configuration.
Expected outcome: Pressure returns to baseline when the restrictive accessory is removed.
If an accessory caused the problem, replace it, verify normal operation, and stop.
6. Check the Bag/Vent Switch and APL Valve
Confirm that the Bag/Vent switch moves completely into the selected position and is not obstructed.
During manual ventilation:
- Verify that the adjustable pressure-limiting valve is not set unnecessarily high.
- Confirm that the APL valve rotates normally and is not physically damaged or contaminated.
- Test whether pressure releases appropriately when the APL setting is reduced.
The APL valve controls pressure limitation during manual ventilation and is adjustable up to 70 cmH₂O.
Expected outcome: Manual-circuit pressure responds appropriately to the APL setting.
If elevated pressure occurs only during manual ventilation and corrects when the APL valve is adjusted, verify operation and stop.
7. Inspect the Breathing System Assembly
With the machine removed from clinical use, inspect externally accessible breathing-system components for:
- Improper seating or incomplete latching.
- Misaligned breathing-system parts.
- Pinched or displaced seals.
- Residual moisture.
- Debris or contamination.
- Components installed incorrectly after cleaning.
- Cracks or visible physical damage.
Reseat removable assemblies according to approved facility practices and the manufacturer’s operating instructions. Do not perform internal valve or board-level disassembly.
Expected outcome: The breathing system is fully seated, correctly assembled, and free of visible obstruction.
If reseating the assembly resolves the issue, perform a complete machine checkout and stop.
8. Inspect the Bellows and Ventilator Components Externally
Observe the bellows while ventilating a test lung.
Check for:
- Incomplete bellows refill.
- Delayed or restricted bellows movement.
- Bellows sticking to the housing.
- Water or contamination in the bellows chamber.
- Visible folds, distortion, or damage.
- Abnormal pressure remaining between breaths.
Do not disassemble internal ventilator valves during initial Clinical Engineering troubleshooting.
Expected outcome: The bellows rises and falls smoothly and airway pressure returns to the selected PEEP level after each breath.
Abnormal bellows movement that remains after external causes are removed requires bench evaluation.
9. Evaluate the Scavenging Connection
Inspect the anesthetic gas scavenging system for:
- Excessive suction.
- Restricted or kinked scavenging tubing.
- Incorrect hose connections.
- A full or obstructed transfer hose.
- Improperly adjusted active scavenging flow.
- A blocked or malfunctioning receiving system.
- Changes when the wall scavenging connection is removed for a controlled off-patient test.
Excessive or restricted scavenging can interfere with breathing-system pressure and bellows operation.
Expected outcome: Scavenging operates without creating abnormal positive or negative pressure in the breathing system.
If correcting the scavenging connection resolves the problem, verify the machine with the intended scavenging system and stop.
10. Check for Moisture or Contamination
Inspect accessible breathing-system components, valves, flow sensors, hoses, and bellows areas for moisture or contamination.
Allow approved reusable components to dry completely before reinstallation. Replace contaminated disposable components.
Do not apply lubricants, solvents, or compressed air unless specifically approved by the manufacturer.
Expected outcome: Components are clean, dry, correctly installed, and move freely.
If moisture removal resolves the issue, complete the required checkout and document the finding.
11. Test With Known-Good External Components
Use known-good compatible components to isolate the problem:
- Breathing circuit.
- Filters.
- Breathing bag.
- Test lung.
- Scavenging hose.
- Removable breathing-system components when exchange is permitted.
Change one component at a time so the cause can be identified.
Expected outcome: The elevated pressure follows a defective external component or disappears when that component is replaced.
If the defective component is identified, replace it, verify normal operation, and stop.
12. Run the Complete Preoperative Checkout
After correcting any external issue:
- Reassemble the machine completely.
- Connect verified gas supplies and scavenging.
- Install a known-good circuit and test lung.
- Run the complete automated machine checkout.
- Test manual and mechanical ventilation.
- Verify selected and measured PEEP.
- Confirm that airway pressure returns to baseline.
- Confirm proper bellows operation.
- Verify alarms and pressure-limit functions.
Expected outcome: The Aisys CS2 passes checkout and maintains stable expiratory pressure in all tested modes.
Do not return the machine to clinical service if elevated pressure remains, checkout fails, or ventilation performance is inconsistent.
If the Problem Persists
If elevated PEEP remains after settings, breathing circuits, accessories, breathing-system installation, moisture, bellows operation, and scavenging have been checked, common external causes have been ruled out.
The problem may involve an internal expiratory valve, ventilator control component, pressure-sensing pathway, breathing-system mechanism, or electronic control fault.
The device should be:
- Removed from service.
- Labeled Out of Service.
- Sent for qualified repair or bench evaluation.
- Evaluated using approved GE Healthcare service documentation and test equipment.
Knowing when to stop external troubleshooting and escalate the repair is proper Clinical Engineering practice.
Clinical Use Tip
Never investigate persistent elevated expiratory pressure while the machine is actively ventilating a patient. Move the patient to verified alternate equipment before manipulating circuits, valves, scavenging connections, or breathing-system components.
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 displayed elevated PEEP and airway pressure did not return to the selected baseline between breaths."
Cause
What was observed during troubleshooting.
Example:
"Inspection found a moisture-saturated expiratory bacterial filter restricting gas flow from the breathing circuit."
Resolution
What action was taken.
Example:
"Replaced the expiratory filter, installed a known-good circuit, completed the automated checkout, and verified normal PEEP and pressure release using a test lung."
Helpful Details to Include (If Known)
- Selected and measured PEEP.
- Ventilation mode and settings.
- Complete alarm message.
- Whether the issue occurred in manual or mechanical ventilation.
- Circuit and filters inspected or replaced.
- Moisture or contamination found.
- Bag/Vent switch and APL response.
- Bellows movement.
- Scavenging condition.
- Results of the automated checkout.
- Final device status.
Final Thought
Elevated expiratory pressure can result from simple restrictions, incorrect settings, moisture, or improperly installed components, but it can directly affect ventilation and patient safety. A logical external-first approach identifies correctable causes while preventing unnecessary internal repair. Clear CCR documentation preserves the evidence supporting repair, escalation, and the final service decision.
That is successful troubleshooting.