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What This Guide Helps With
Troubleshoot inaccurate or unstable arterial or venous pressure readings caused by tubing, pressure connections, air, clamping, disposable setup, or patient-circuit conditions.
Step-by-Step Troubleshooting
1. Protect the Patient
Do not rely on unstable or clearly incorrect arterial or venous pressure monitoring during dialysis. If the issue occurs during treatment, clinical staff should assess the patient and extracorporeal circuit and follow facility procedure for safely stopping or transferring treatment when required.
Technical troubleshooting should occur off patient whenever device performance is uncertain.
Expected outcome: The patient is not dependent on unreliable pressure monitoring during troubleshooting.
2. Confirm Which Pressure Channel Is Affected
Determine whether the issue involves:
- Arterial pressure
- Venous pressure
- Both channels
- A fixed or implausible reading
- Excessive fluctuation
- A reading that changes with tubing movement
- A problem appearing only during pump operation
Record the exact reported behavior.
Expected outcome: The affected channel and failure pattern are identified.
3. Inspect the Extracorporeal Tubing Setup
With the machine off patient, inspect the blood tubing and pressure-monitoring portions of the disposable setup for:
- Kinks
- Clamps left closed
- Twisted tubing
- Loose connections
- Incorrect routing
- Collapsed segments
- Visible damage
Expected outcome: The tubing path is installed correctly and free of obvious restrictions. If correcting an external setup issue stabilizes pressure readings, troubleshooting can stop after verification.
4. Inspect Pressure Connections and Interfaces
Check accessible pressure interfaces and connections for secure seating, contamination, moisture, loose fittings, or incorrectly installed disposable components.
Do not open internal pressure-sensing assemblies.
Expected outcome: Pressure interfaces are clean, dry, properly connected, and mechanically secure.
5. Check for Air or Fluid Where It Should Not Be
Inspect accessible pressure-monitoring portions of the circuit for abnormal air or fluid conditions that may interfere with pressure transmission.
Use normal setup procedures only; do not improvise purging or pressure-source methods.
Expected outcome: The disposable pressure-monitoring path is in the expected setup condition.
6. Replace the Suspect Disposable
If the tubing or pressure interface remains questionable, replace the disposable set with a new approved set and repeat setup.
This is particularly useful when a problem follows one specific tubing set.
Expected outcome: Stable pressure behavior with the replacement disposable indicates the original disposable or setup caused the condition.
7. Observe Pressure Behavior During Normal Off-Patient Testing
Use the normal machine preparation or approved functional test process to observe whether the affected reading responds consistently.
Do not apply unapproved pressure sources or enter unauthorized calibration functions.
Expected outcome: Pressure readings behave consistently and no longer fluctuate abnormally.
8. Check Related Pump and Clamp Conditions
Confirm there is no simultaneous blood-pump, tubing, or clamp problem that could account for abnormal pressure behavior.
A pressure alarm may be the result of an actual flow restriction rather than a failed pressure sensor.
Expected outcome: Other external components that influence circuit pressure are operating normally.
9. Perform Final Functional Verification
Complete the normal pre-treatment verification sequence and confirm arterial and venous pressure monitoring is stable with the approved setup.
Expected outcome: Both pressure channels operate consistently with no unexplained alarm or instability. Troubleshooting can stop.
10. Escalate Persistent Pressure-Monitoring Problems
If the disposable, pressure connections, tubing path, and related external conditions are satisfactory but readings remain unreliable, remove the machine from service.
Expected outcome: Internal sensing, pneumatic interface, signal processing, calibration, or other service-level problems are referred for qualified evaluation.
If the Problem Persists
Common external tubing, disposable, connection, air/fluid, clamping, and flow-related causes have been ruled out. A persistent problem may involve internal pressure sensing, signal processing, pneumatic control, calibration, or associated electronics.
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for repair or bench evaluation
- Evaluated using appropriate Outset Medical documentation and approved test equipment
- Repaired or calibrated only by qualified personnel
Pressure-monitoring accuracy and applicable dialysis safety functions must be verified before return to service. Knowing when to stop external troubleshooting is proper troubleshooting.
Clinical Use Tip
Pressure alarms may reflect a real extracorporeal-circuit restriction; confirm the circuit condition before assuming the monitor is inaccurate.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Staff reported the Tablo displayed an unstable venous pressure value that changed significantly with minor tubing movement."
Cause
What was observed during troubleshooting.
Example:
"Clinical Engineering found the venous pressure connection on the disposable was incompletely seated."
Resolution
What action was taken.
Example:
"Installed the pressure connection correctly, repeated setup, verified stable arterial and venous pressure monitoring, and returned the machine to service."
Helpful Details to Include (If Known)
- Arterial, venous, or both channels affected
- Reported pressure behavior
- Whether condition occurred with pump running
- Tubing condition and routing
- Pressure connection condition
- Presence of air or fluid abnormality
- Known-good disposable substitution
- Related pump or clamp alarms
- Results after correction
- Final device status
Final Thought
Unstable dialysis pressure readings require verification of the entire external blood-circuit setup before an internal sensor is blamed. Protect the patient, rule out real flow restrictions and disposable problems, verify stable monitoring after correction, and escalate unresolved sensing issues appropriately.
That is successful troubleshooting.