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What This Guide Helps With
Troubleshooting absent, incomplete, or irregular bellows movement caused by ventilation settings, circuit leaks, breathing-system assembly, gas supply, or external components.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended bellows or ventilator troubleshooting while the WATO EX Series is supporting an active patient.
If the bellows stop rising or cycling during clinical use:
- Notify the anesthesia provider immediately.
- Confirm whether ventilation, airway pressure, oxygen concentration, and capnography remain clinically adequate.
- Begin ventilation with an approved backup method or another verified anesthesia machine.
- Maintain independent patient monitoring.
- Follow the facility’s anesthesia-equipment failure procedure.
Expected outcome: Patient care no longer depends on an anesthesia machine with uncertain ventilation.
Continue troubleshooting only after the machine has been removed from active patient use.
2. Confirm the Exact Failure Condition
Determine whether:
- The bellows do not rise during filling.
- The bellows rise only partially.
- The bellows rise but do not compress during inspiration.
- The bellows cycle irregularly.
- The problem occurs only in mechanical ventilation.
- A ventilator, pressure, volume, gas-supply, or leak alarm is displayed.
Record the complete alarm or advisory message before restarting the machine.
Expected outcome: The failure pattern is clearly identified and can guide the remaining checks.
3. Verify Ventilation Mode and Basic Settings
Confirm that:
- Mechanical ventilation is selected.
- The ventilation mode is appropriate for testing.
- Tidal volume or inspiratory pressure is set high enough to produce visible movement.
- Respiratory rate is above zero.
- Inspiratory time and other timing settings are reasonable.
- The machine is not in standby or manual/spontaneous ventilation.
Use a manufacturer-approved test lung instead of a patient.
Expected outcome: The ventilator initiates breaths and the bellows begin cycling.
If normal operation returns, complete the required system checkout and stop troubleshooting.
4. Check the Bag/Ventilator Selection Control
Confirm that the bag/ventilator selector is fully positioned in the ventilator setting.
Move the selector through its normal range and return it firmly to the ventilator position. Do not force the control.
A selector left between positions may prevent proper ventilator operation or redirect breathing-system flow.
Expected outcome: Mechanical ventilation engages and the bellows cycle normally.
5. Verify Fresh-Gas and Drive-Gas Supplies
Check that:
- Oxygen and air pipeline hoses are fully connected.
- Pipeline pressure indicators are within the facility’s acceptable range.
- Backup cylinders are installed and contain adequate pressure when required.
- No gas-supply alarm is active.
- Fresh-gas flow is present.
The WATO EX family is available in several configurations, so gas sources and installed features may vary by model.
Expected outcome: Adequate gas supply is available and gas-related alarms clear.
If the bellows begin operating after restoring the gas supply, perform the complete pre-use checkout before returning the unit to service.
6. Inspect the Patient Breathing Circuit
Inspect the entire circuit from the inspiratory and expiratory ports to the test lung.
Look for:
- Disconnected tubing
- Loose fittings
- Split or punctured hoses
- Open sampling or accessory ports
- Incorrectly installed filters
- Water accumulation
- Kinked or obstructed tubing
- A damaged or disconnected reservoir bag
- Incorrect circuit assembly
Reconnect or replace questionable external components with compatible, approved accessories.
Expected outcome: The breathing circuit is complete, unobstructed, and capable of holding pressure.
7. Check for a Major Breathing-System Leak
Occlude the patient connection using the approved test method and perform the machine’s system checkout or leak test.
Pay particular attention to:
- Circuit connections
- Reservoir bag and bag connection
- Absorber canister seating
- Drain ports
- Manual bag connection
- Breathing-system seals
- Bellows housing and visible bellows condition
- Accessory and sampling connections
Do not continue mechanical ventilation testing if the breathing system cannot pass the required leak test.
Expected outcome: The system passes its leak test and the bellows rise normally between breaths.
8. Inspect the Bellows Assembly Externally
With the machine powered off and removed from service, visually inspect the accessible bellows assembly.
Confirm that:
- The bellows are properly seated.
- The bellows housing is installed and secured.
- No visible fold, tear, deformation, or sticking is present.
- The housing is free of foreign material and excessive moisture.
- The bellows move freely within their normal external travel without being forced.
- No breathing-system component was incorrectly reinstalled after cleaning.
Do not disassemble internal ventilator or drive-gas components unless authorized by the applicable Mindray service documentation.
Expected outcome: The bellows and housing are visibly intact, correctly installed, and free from obstruction.
9. Check the Absorber and Breathing-System Assembly
Confirm that:
- The absorber canister is fully installed and latched.
- The breathing-system assembly is seated correctly.
- Drain plugs or water traps are closed and properly installed.
- Inspiratory and expiratory valve components are present and correctly seated.
- No seal, valve disc, or external component was omitted after cleaning.
- Soda lime or absorbent has not entered the valve or bellows area.
Incorrect seating or assembly can create a substantial leak or restrict gas movement.
Expected outcome: The breathing system is assembled correctly and the bellows fill and cycle normally.
10. Inspect Expiratory Flow and Exhaust Paths
Check the accessible expiratory path for:
- Kinked tubing
- Water accumulation
- Occluded filters
- Incorrectly installed one-way valve components
- Blocked exhaust or scavenging connections
- Excessive suction applied through the scavenging system
Temporarily substitute known-good compatible external tubing or filters when appropriate.
Do not operate the machine clinically with the scavenging system disconnected unless specifically permitted by facility procedures and the manufacturer’s instructions.
Expected outcome: Gas can exit the breathing system normally without excessive restriction or suction.
11. Run the Automated System Checkout
After correcting external issues:
- Reassemble the breathing system completely.
- Attach an approved test lung.
- Confirm adequate gas supplies.
- Power-cycle the machine using the normal shutdown and startup process.
- Complete the required automated and manual pre-use checks.
- Test multiple breaths while observing bellows movement, airway pressure, inspired volume, expired volume, and alarms.
Expected outcome: The machine completes checkout, delivers consistent breaths, and the bellows rise and compress normally.
Do not return the unit to service solely because the bellows move. All required checkout tests and performance verification must pass.
If the Problem Persists
If the bellows still do not rise or cycle after settings, gas supplies, circuit connections, leaks, breathing-system assembly, valves, absorber seating, and external restrictions have been checked, common external causes have been ruled out.
The problem may involve an internal ventilator valve, drive-gas circuit, pneumatic control component, pressure sensor, flow sensor, electronic control system, or internal seal.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for qualified repair or bench evaluation
- Evaluated using the correct Mindray service documentation and calibrated test equipment
Knowing when to stop and escalate is proper troubleshooting. Do not continue internal disassembly without appropriate training, authorization, and service information.
Clinical Use Tip
Never troubleshoot unreliable bellows movement on an active patient. Move the patient to another verified anesthesia machine or approved ventilation method before disconnecting circuits, testing gas supplies, or running checkout procedures.
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 bellows did not rise and the ventilator was not cycling during setup."
Cause
What was observed during troubleshooting.
Example:
"Inspection found the absorber assembly incompletely seated, creating a breathing-system leak that prevented the bellows from filling."
Resolution
What action was taken.
Example:
"Reseated and secured the absorber assembly, completed the system leak test and automated checkout, verified consistent ventilation with a test lung, and returned the machine to service."
Helpful Details to Include (If Known)
- Exact WATO EX model
- Complete alarm or advisory message
- Ventilation mode and settings
- Whether the problem occurred during checkout or clinical use
- Pipeline and cylinder pressures
- Outlet and AC power tested
- Bag/ventilator selector position
- Circuit and test lung used
- Absorber seating verified
- Leak-test result
- Bellows movement observed
- Inspired and expired volume readings
- Airway-pressure behavior
- Scavenging configuration
- Unusual sounds
- Unusual heat or smell
- Components replaced or swapped
- Final device status
Final Thought
Patient safety comes first whenever bellows movement or ventilation is unreliable. A logical evaluation of settings, gas supplies, circuits, leaks, breathing-system assembly, and external restrictions can resolve many failures without unnecessary disassembly. When the machine cannot pass checkout, remove it from service, escalate appropriately, and document the complaint, cause, and resolution clearly.
That is successful troubleshooting.