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What This Guide Helps With
Troubleshooting elevated airway-pressure alarms caused by blocked circuits, restrictive accessories, incorrect settings, APL valve position, scavenging problems, or equipment faults.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended troubleshooting while the Perseus is ventilating an active patient.
Have the anesthesia provider:
- Assess the patient and airway immediately.
- Begin ventilation using an alternate approved method when necessary.
- Transfer the patient to another verified anesthesia machine or ventilator if equipment performance is uncertain.
Expected: Patient ventilation is maintained without depending on equipment displaying unresolved pressure alarms.
Why it matters: High airway pressure can result from either a patient condition or an equipment or circuit problem. Clinical causes must be evaluated by the anesthesia provider before Clinical Engineering begins equipment troubleshooting.
If alternate ventilation is established, continue evaluation away from the patient.
2. Confirm the Exact Alarm and Operating Conditions
Record the complete alarm message before clearing or restarting the machine.
Determine whether the display shows:
- Airway pressure high
- Airway pressure continuously high
- Another related alarm such as PEEP or CPAP high
Also document:
- Ventilation mode
- Displayed PIP and airway-pressure waveform
- Paw high alarm limit
- Set inspiratory pressure or tidal volume
- PEEP
- Whether the alarm occurred during automatic ventilation or MAN/SPON
- Whether the problem occurred during a case, checkout, or bench test
Expected: The specific alarm condition and circumstances are clearly identified.
3. Inspect the Patient Circuit for Obstruction
With the machine removed from patient use, inspect the complete breathing pathway.
Check for:
- Kinked, crushed, or twisted breathing hoses
- A blocked endotracheal-tube connector or test-lung connection
- Occluded Y-piece, elbow, or adapter
- Excessive water accumulation
- Protective caps or plugs left installed
- Internally collapsed hoses
- Foreign material inside accessible connectors
Straighten or replace any questionable component.
Expected: The inspiratory and expiratory pathways are open and unrestricted.
If removing the obstruction resolves the alarm during controlled testing, complete the system test and stop troubleshooting.
4. Check Filters, HMEFs, and Added Accessories
Inspect all filters, HMEFs, adapters, sampling connectors, and other accessories installed in the circuit.
Look for:
- Wet or visibly contaminated filters
- Excessive resistance
- Incorrect patient-size accessories
- Multiple filters installed in series
- Accessories added since the last successful use
- Components installed backward or in the wrong location
Replace suspect disposable components with approved known-good accessories.
Expected: The circuit operates normally without unnecessary resistance.
If replacing a restrictive accessory resolves the alarm, complete functional testing and stop.
5. Verify Circuit Connections and Component Seating
Confirm that:
- The inspiratory hose is connected to the inspiratory port.
- The expiratory hose is connected to the expiratory port.
- Connections are fully seated.
- The breathing system is properly installed.
- The absorber and other removable operating components are correctly seated.
- No component appears displaced following cleaning or reassembly.
Do not perform internal disassembly or force components into position.
Expected: The breathing system and circuit are assembled correctly with no visible obstruction or misconnection.
6. Inspect the Breathing Bag and Bag Hose
Check that the breathing bag:
- Is attached securely
- Hangs freely
- Is not folded, trapped, or pinched
- Is not obstructed by cables or breathing hoses
- Can inflate and deflate during an approved bench test
Expected: The breathing bag moves freely without restricting the system.
If repositioning or replacing the bag assembly resolves the issue, complete the required system test and stop.
7. Verify Ventilation Settings and the Paw Alarm Limit
Have the anesthesia provider confirm the clinical settings when the event occurred. During bench evaluation, use facility-approved test settings.
Review:
- Paw high alarm limit
- Pmax or Pinsp
- Tidal volume
- PEEP
- Respiratory rate
- Inspiratory time or I ratio
- Flow and pressure-support settings, when applicable
Confirm that the upper Paw alarm limit is appropriate for the expected test pressure and has not been accidentally set below the normal PIP.
Do not independently change prescribed patient settings merely to suppress an alarm.
Expected: The alarm limit is appropriate, and the selected ventilation settings do not intentionally produce excessive pressure.
8. Check the APL Valve in MAN/SPON Mode
The APL valve affects pressure limitation during manual ventilation and spontaneous breathing.
When evaluating MAN/SPON operation:
- Confirm the APL setting is appropriate for the test.
- Check that the control turns normally without binding.
- Confirm that it is not unintentionally set to a high pressure.
- Check for visible contamination, damage, or incorrect assembly.
- Do not force, lubricate, or internally disassemble the valve.
Expected: Pressure is properly relieved and limited during an approved manual-ventilation test.
If the APL valve binds, does not relieve pressure, or behaves inconsistently, remove the machine from service.
9. Check the O2 Flush Control
Inspect the O2 flush button for:
- Physical damage
- A button that remains depressed
- Binding or delayed return
- Objects pressing against the control
During controlled testing, verify that the button releases immediately when no longer pressed.
Expected: The O2 flush operates only while intentionally activated and returns normally.
If the control sticks or activates unexpectedly, stop testing and remove the machine from service.
10. Inspect the Anesthetic Gas Scavenging Path
Check the external scavenging system for:
- Kinked or crushed AGS hoses
- Blocked connections
- An incorrectly connected scavenging hose
- A closed or obstructed terminal connection
- Fluid or debris in accessible tubing
- Recent changes to the room scavenging connection
Compare the setup with a known-good operating room connection when available. Do not adjust internal scavenging components without the applicable service procedure and authorization.
Expected: Waste gas can leave the machine without an external restriction.
If correcting the external scavenging connection resolves the alarm, complete functional testing and stop.
11. Test With Known-Good Accessories
Install an approved known-good:
- Breathing circuit
- Breathing bag
- Filter configuration
- Test lung
Use controlled adult or pediatric test settings appropriate for the test equipment.
Observe:
- PIP
- PEEP
- Pressure waveform
- Delivered and exhaled tidal volume
- Whether pressure returns to baseline during expiration
- Whether the alarm occurs during both automatic and MAN/SPON ventilation
Expected: Normal pressure delivery without repeated pressure alarms.
If the machine passes with known-good accessories, the original circuit or accessory configuration was likely responsible.
12. Perform the System Test and Final Functional Check
After replacing or reconnecting breathing-system components:
- Run the complete machine system test.
- Confirm the leakage and compliance results are acceptable.
- Repeat ventilation using a test lung.
- Verify alarm activation using an approved pressure-limit test.
- Confirm pressure is released properly when the obstruction is removed.
- Review the alarm log for recurring pressure-related messages.
Expected: The Perseus completes its system test and ventilates normally without unexplained elevated pressure.
Return the machine to service only after all required tests pass.
If the Problem Persists
If the alarm continues with known-good circuits, filters, accessories, test lungs, appropriate settings, and an unrestricted scavenging connection, common external causes have been ruled out.
A fault may involve the:
- Pressure-measurement system
- Ventilator or blower assembly
- Internal inspiratory or expiratory valve
- APL valve assembly
- Internal breathing-system obstruction
- Control electronics
The machine should be:
- Removed from service
- Labeled Out of Service
- Sent for qualified bench evaluation or Drager service
- Kept out of clinical use until all required performance and safety tests pass
Do not perform unauthorized internal disassembly. Knowing when to stop and escalate is proper troubleshooting.
Clinical Use Tip
Never troubleshoot a persistent high-pressure alarm while the machine remains responsible for an active patient. Establish alternate ventilation first and allow the anesthesia provider to assess patient, airway, and tube-related causes.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Anesthesia staff reported repeated high airway pressure and continuously high airway pressure alarms during pre-use ventilation testing."
Cause
What was observed during troubleshooting.
Example:
"Inspection found a wet, occluded expiratory filter that restricted circuit flow and caused elevated airway pressure during test-lung ventilation."
Resolution
What action was taken.
Example:
"Replaced the filter, inspected the breathing circuit and scavenging connections, completed the Perseus system test, and verified normal ventilation and pressure-alarm operation with a test lung."
Helpful Details to Include (If Known)
- Exact alarm message and priority
- Ventilation mode
- Paw high alarm limit
- PIP, PEEP, and tidal-volume readings
- Pressure waveform behavior
- Circuit and filter type
- Circuit inspected or swapped
- Breathing bag condition
- APL valve setting and movement
- O2 flush condition
- Scavenging hose and terminal condition
- System-test and leakage-test results
- Whether the problem followed reprocessing
- Unusual sounds, heat, or smell
- Final device status
Final Thought
High airway pressure may originate from the patient, breathing circuit, settings, scavenging pathway, or anesthesia machine. Protect the patient first, eliminate visible restrictions logically, verify operation with known-good accessories, and escalate persistent faults with complete documentation.
That is successful troubleshooting.