Smiths Medical Medfusion 4000

Asset Type

Infusion Pump

Manufacturer

Smiths Medical

Model

Medfusion 4000

What This Guide Helps With

This guide helps troubleshoot the Occlusion - Check Infusion Line alarm on a Smiths Medical Medfusion 4000 infusion pump. This alarm indicates that the force sensor in the plunger driver sensed an occlusion because the force value exceeded the configured limit.

The condition may be caused by a closed clamp, kinked tubing, blocked extension set, catheter resistance, high pressure setup, syringe loading issue, inappropriate occlusion configuration, or force sensing problem.

Step-by-Step Troubleshooting

Ensure Patient Safety First

• If the pump is actively infusing and an occlusion alarm is present, notify clinical staff immediately.
• Do not silence, bypass, or repeatedly restart the pump without confirming that the infusion path is safe.
• If medication delivery is critical, clinical staff should transfer the infusion to another verified pump or establish an alternate infusion method.
• Expected outcome: Patient therapy is protected while the occlusion condition is evaluated.

Verify the Reported Alarm and Behavior

• Confirm the display shows Occlusion - Check Infusion Line.
• Observe whether the alarm occurs immediately after pressing start, after several minutes of infusion, only at higher rates, or only with certain syringes, tubing, fluids, or clinical setups.
• Identify whether infusion stops, pressure appears high, syringe plunger movement feels restricted, the line is visibly kinked or clamped, or the alarm clears temporarily and returns.
• Expected outcome: The alarm behavior is confirmed and clearly documented.

Check the Infusion Line for Simple External Causes

• Inspect the entire infusion path from syringe to patient connection.
• Look for closed clamps, partially closed roller clamps, kinked tubing, pinched tubing, tubing caught in bed rails, stopcocks in the wrong position, blocked extension sets, or loose tubing connections.
• Correct obvious restrictions only with clinical staff awareness and restart the infusion only if clinical staff confirms it is safe.
• Expected outcome: The alarm clears if the cause was a simple downstream restriction.

Check the Syringe and Pump Loading

• Verify the syringe barrel is seated correctly.
• Confirm the syringe flange is secured in the flange holder.
• Confirm the plunger is fully captured by the plunger holders.
• Verify the syringe size and model match the pump selection.
• Check that the plunger driver is not binding against the syringe and that no physical obstruction is preventing smooth plunger movement.
• Expected outcome: Syringe position is correct and the plunger driver moves smoothly during operation.

Check for Catheter or Patient-Side Resistance

• Have clinical staff assess the patient-side access before assuming the pump is faulty.
• Clinical staff should check for infiltration, occluded catheter, restricted IV site, closed access device, resistance when flushing, incorrect catheter size, or patient positioning that restricts flow.
• Expected outcome: Patient-side access is patent and appropriate for the infusion.

Review the Infusion Setup, Fluid, and Rate

• Check whether the alarm occurs only with a specific infusion setup.
• Review the infusion rate, syringe size, tubing bore size, extension set length, filters, medication viscosity, fluid concentration, catheter size, and total line length.
• Small tubing, long extension sets, viscous fluids, high rates, or small catheters can increase pressure enough to trigger an occlusion alarm.
• Expected outcome: The tubing, catheter, syringe, and fluid type are appropriate for the programmed rate.

Check Occlusion Alarm Configuration

• Review the configured occlusion pressure or force limit if the alarm appears too sensitive or inconsistent with the clinical setup.
• Confirm the setting is appropriate for facility policy, medication type, clinical care area, syringe type, infusion profile, or drug library configuration.
• Do not change configuration settings without following facility policy and approval workflow.
• Expected outcome: Occlusion alarm settings match the intended clinical use and facility configuration.

Consider FlowSentry Pressure Monitoring if Used

• If the pump is configured for or equipped with FlowSentry pressure monitoring, verify the pressure monitoring setup is correct.
• Check the pressure sensing setup, pressure tubing or accessory connection, compatible tubing or accessory use, displayed pressure trend, and whether pressure rises before the alarm.
• Expected outcome: Pressure monitoring behavior matches the infusion condition.

Check for Mechanical Binding or Physical Damage

• Inspect the pump externally for cracked syringe holder components, damaged plunger driver, sticky or contaminated plunger mechanism, fluid intrusion, loose syringe clamp components, or recent drop damage.
• Listen for unusual noise during plunger movement.
• Do not disassemble the pump during clinical troubleshooting.
• Expected outcome: The syringe mechanism moves freely and shows no visible damage.

Check Force Sensor Calibration if the Alarm Recurs

• If actual occlusion, catheter resistance, line setup, syringe loading, and configuration issues have been ruled out, evaluate the force sensor through the approved Biomed process.
• Use Biomed > Calibration > Calibrate Force Sensor only according to facility procedure.
• Verify the pump passes required operational checks after calibration.
• Expected outcome: Force sensor calibration completes successfully and the pump no longer falsely reports occlusion.

Stop When Resolved

• If the alarm is corrected by opening a clamp, removing a kink, changing tubing setup, correcting syringe loading, resolving catheter resistance, or completing approved force sensor calibration, stop troubleshooting.
• Verify the alarm no longer occurs, the infusion runs without repeated occlusion alarms, the syringe mechanism operates smoothly, and no unresolved configuration issue remains.
• Return the pump to service only after safe function is confirmed.

If the Problem Persists

If the Occlusion - Check Infusion Line alarm continues after external causes, line setup, catheter resistance, syringe loading, configuration, and force sensor calibration have been ruled out, the issue may involve the force sensing system or plunger drive mechanism.

Remove the pump from service.

Label it Out of Service.

Send it for repair or bench evaluation.

Persistent occlusion alarms may indicate force sensor failure, plunger driver mechanical binding, plunger mechanism damage, internal contamination, calibration failure, plunger PCB issue, or Main PCB signal processing issue.

Clinical Use Tip

Never troubleshoot on an active patient. Move the patient to a backup device first if infusion delivery is interrupted or the occlusion alarm cannot be safely resolved at the bedside.

Do not repeatedly restart an infusion after an active occlusion alarm without confirming line patency, catheter condition, and medication delivery safety.

Work Order Documentation (CCR Method)

CCR = Complaint, Cause, Resolution

Complaint

What was reported by the clinical staff.

Example:
"Medfusion 4000 infusion pump reported Occlusion - Check Infusion Line during infusion. User stated pump stopped delivery and alarm returned after restart."

Cause

What was observed during troubleshooting.

Example:
"Force sensor detected pressure above configured occlusion limit. Infusion line was found kinked near the patient connection, causing downstream restriction."

Resolution

What action was taken.

Example:
"Removed kink from infusion line, verified syringe was loaded correctly, confirmed alarm cleared, and ran pump without repeated occlusion alarm. Device returned to service."

Helpful Details to Include (If Known)

• Alarm behavior
• Accessories swapped
• Power behavior
• Environmental factors
• Indicator lights
• Final device status

Final Thought

Occlusion alarms should be treated as possible therapy interruptions until proven otherwise. Start with the infusion path, syringe loading, catheter resistance, clinical setup, and configuration before suspecting device failure. If the alarm continues after common causes are ruled out, approved force sensor calibration or repair escalation may be needed. Clear CCR documentation helps show whether the issue was clinical setup, configuration, calibration, or a true device fault.

That is successful troubleshooting.