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What This Guide Helps With
Troubleshooting elevated measured PEEP or incomplete exhalation caused by settings, circuit restrictions, breathing-system components, scavenging, or external accessory problems.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended troubleshooting while the WATO EX Series anesthesia machine is supporting an active patient.
If elevated PEEP or expiratory pressure occurs during a procedure:
- Notify the anesthesia provider immediately.
- Confirm ventilation using airway-pressure waveforms, capnography, chest movement, oxygen saturation, and available independent monitoring.
- Check for signs of incomplete exhalation or progressively increasing airway pressure.
- Move the patient to another verified anesthesia machine or approved ventilation method if safe ventilation cannot be confirmed.
- Follow the facility’s anesthesia-equipment failure procedure.
Expected outcome: Patient care no longer depends on equipment with unresolved expiratory-pressure performance.
Continue troubleshooting only after the machine has been removed from active patient use.
2. Confirm the Reported Pressure Condition
Record:
- Selected ventilation mode
- Set PEEP
- Measured PEEP
- Peak, mean, and plateau airway pressures
- Respiratory rate
- I ratio or inspiratory time
- Fresh-gas flow
- Complete alarm or advisory message
- Whether pressure returns to baseline between breaths
The WATO EX Series uses electronically controlled PEEP on applicable configurations, with model-dependent settings and monitoring capabilities.
Expected outcome: The exact difference between selected and measured PEEP is identified.
If the measured PEEP matches the selected setting and the device passes checkout, confirm the intended clinical setting with the anesthesia provider before proceeding.
3. Verify the PEEP and Ventilation Settings
Confirm that:
- PEEP is set to the intended value.
- The correct patient category and ventilation mode are selected.
- Respiratory rate is not excessively high.
- Inspiratory time is not too long.
- The I ratio provides enough expiratory time.
- Pressure-support, CPAP, or apnea-backup settings are appropriate.
High respiratory rates or insufficient expiratory time can prevent the test lung from fully emptying and create apparent auto-PEEP.
Expected outcome: Pressure returns to the selected baseline between breaths.
If correcting an unintended setting resolves the issue, complete a full system checkout and stop troubleshooting.
4. Inspect the Patient Breathing Circuit
Remove and inspect the complete breathing circuit for:
- Kinked or compressed tubing
- Water accumulation
- Obstructed filters
- Incorrectly installed adapters
- Restricted Y-piece or elbow
- Damaged inner tubing in coaxial circuits
- Accessories with excessive resistance
- Incorrect inspiratory or expiratory limb connections
Replace questionable components with known-good compatible accessories.
Expected outcome: The circuit is open, correctly assembled, and free of restrictions.
If replacing the circuit resolves the elevated pressure, complete checkout and return the machine to service only after satisfactory testing.
5. Remove Unnecessary External Accessories
Temporarily remove or replace, as appropriate:
- Heat-and-moisture exchangers
- Bacterial or viral filters
- Flexible catheter mounts
- Sampling adapters
- Excessively long circuit extensions
- External PEEP valves
- Nebulizer adapters
Use a manufacturer-compatible test circuit and test lung.
Expected outcome: Measured PEEP returns to the selected value when the restrictive accessory is removed.
Do not return a visibly contaminated, wet, damaged, or restricted accessory to service.
6. Check the Expiratory Limb and Expiratory Port
Inspect the expiratory limb from the patient connection back to the breathing system.
Confirm that:
- The expiratory hose is not kinked.
- No pooled water is obstructing flow.
- The expiratory port is unobstructed.
- The expiratory flow sensor is correctly seated and oriented.
- The flow sensor is clean and dry according to approved handling procedures.
- All breathing-system components are fully installed and latched.
Do not insert tools into ports or attempt internal valve disassembly.
Expected outcome: Exhaled gas can move freely through the expiratory pathway.
If reseating an externally accessible component resolves the issue, perform the required checkout before returning the device to service.
7. Inspect the Breathing System Assembly
With the device removed from patient use, visually inspect accessible components for:
- Improperly installed absorber canister
- Misaligned seals
- Loose breathing-system connections
- Incorrectly seated valve covers
- Visible debris or moisture
- Damaged disposable components
- Components installed after cleaning in the wrong position
Compare the assembly with another verified WATO EX unit when available.
Expected outcome: The breathing system is completely assembled with no visible obstruction or misalignment.
8. Evaluate the Scavenging Connection
Inspect the anesthetic gas scavenging system for:
- Kinked transfer tubing
- Incorrect hose routing
- Blocked scavenging tubing
- Excessive suction
- Incorrectly connected disposal hose
- A full or restricted receiving system
- A facility wall connection that is not operating correctly
Test the facility scavenging connection independently when permitted by facility procedure.
Expected outcome: The scavenging system removes waste gas without applying abnormal pressure or suction to the breathing system.
If the fault follows the wall connection or scavenging hose, correct the facility-side problem and repeat checkout.
9. Compare Mechanical and Electronic Pressure Information
Using an approved breathing-circuit analyzer or pressure meter, compare independently measured pressure with the machine’s displayed PEEP.
Confirm that:
- The external analyzer has a current calibration status.
- The analyzer is connected correctly.
- The test lung and circuit are appropriate.
- Several breaths are allowed to stabilize before readings are compared.
Expected outcome: Independent and displayed pressure measurements agree within the applicable acceptance criteria.
If independent pressure is normal but the displayed PEEP remains elevated, suspect a pressure-measurement or calibration problem.
If both measurements are elevated, suspect an actual expiratory restriction or PEEP-control problem.
10. Run the Normal Preuse or System Checkout
Restore the machine to its standard approved test configuration and run the complete normal checkout.
Do not bypass failed tests or repeatedly clear alarms without identifying the cause.
Record:
- Test name
- Pass or fail result
- Displayed error
- Conditions under which the failure occurs
- Whether the failure is repeatable
Expected outcome: The machine passes checkout and maintains the selected PEEP without abnormal residual pressure.
If the machine passes repeatedly and measured pressures are within specifications, return it to service according to facility policy.
If the Problem Persists
If elevated PEEP remains after settings, breathing circuits, accessories, flow sensors, breathing-system assembly, scavenging, and external measurement have been checked, common external causes have been ruled out.
The problem may involve the internal expiratory valve, electronically controlled PEEP system, pressure-sensing pathway, flow measurement, pneumatic control, or ventilator electronics.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for qualified repair or bench evaluation
- Evaluated using the applicable Mindray service documentation and test equipment
Do not continue clinical use based only on the machine completing ventilation when expiratory pressure remains abnormal. Knowing when to stop and escalate is proper troubleshooting.
Clinical Use Tip
Never troubleshoot elevated PEEP on an active patient beyond the immediate checks needed to protect the patient. Transfer ventilation first, then evaluate the machine using a 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 WATO EX Series displayed PEEP above the selected value and airway pressure did not return fully to baseline."
Cause
What was observed during troubleshooting.
Example:
"Inspection found water accumulation and partial obstruction in the expiratory breathing-circuit limb, causing increased resistance during exhalation."
Resolution
What action was taken.
Example:
"Replaced the affected circuit, inspected the expiratory pathway, completed system checkout, and verified selected and measured PEEP using a calibrated breathing-circuit analyzer."
Helpful Details to Include (If Known)
- Complete alarm or message recorded
- Ventilation mode and settings documented
- Set and measured PEEP recorded
- Peak and mean airway pressures recorded
- Pressure waveform reviewed
- Circuit inspected or replaced
- Filters and accessories removed or exchanged
- Flow sensors checked for moisture and proper installation
- Absorber and breathing system inspected
- Scavenging connection tested
- Independent pressure measurement performed
- System checkout result documented
- Unusual sounds, heat, or smell noted
- Final device status documented
Final Thought
Elevated expiratory pressure can result from a simple wet filter or circuit obstruction, but it can also indicate a failed pressure-control component. Protect the patient first, verify the full expiratory pathway logically, compare pressures independently, and escalate when normal operation cannot be proven. Accurate CCR documentation supports safe repair and prevents repeated troubleshooting.
That is successful troubleshooting.