Stryker LIFEPAK 35

Shock Not Delivered

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Asset Type

Defibrillator

Manufacturer

Stryker

Model

LIFEPAK 35

What This Guide Helps With

Troubleshooting failure to deliver a shock by checking safety, power, therapy connections, electrodes, impedance conditions, controls, and reproducibility before repair escalation.

Step-by-Step Troubleshooting

1. Ensure Patient Safety First

Immediately remove the LIFEPAK 35 from active patient reliance if a required shock was not delivered or therapy availability is uncertain.

Provide clinical staff with another verified defibrillator before troubleshooting continues.

Expected: Patient care continues with a known-good defibrillator.

Why it matters: A failed or questionable shock-delivery event is a critical therapy concern. The LIFEPAK 35 is intended to provide defibrillation therapy, so unresolved delivery failure requires controlled evaluation rather than continued clinical reliance.

If the device subsequently appears normal, do not return it to service solely because a power cycle cleared the symptom.

2. Clarify Exactly What “Shock Not Delivered” Means

Interview the reporting clinician and review available device information to determine whether the unit:

Document the selected energy, operating mode, displayed messages, alarm behavior, and whether the problem involved hands-free electrodes or another approved therapy configuration.

Expected: The failure is narrowed to charge, connection, synchronization, control, or discharge behavior.

If the issue is clearly explained by an external setup problem and corrected, continue to controlled verification before considering return to service.

3. Verify Device Power and Readiness

With the unit removed from patient use:

Expected: Stable startup with no unresolved service condition or abnormal power behavior.

If unstable power, repeated resets, or a service indication is present, stop troubleshooting and escalate for bench evaluation.

4. Inspect the Therapy Cable Connection

Power the device down as appropriate for safe handling, then inspect the external therapy path.

Check:

Stryker identifies a dedicated LIFEPAK therapy cable for connecting compatible therapy electrode pads, simulators, and test loads to the LIFEPAK 35, using its TRUE-LOCK cable connector.

Expected: Therapy cable and connector are secure and free of visible damage.

If reseating a loose connection resolves the failure, perform controlled functional verification before stopping.

5. Inspect the Therapy Electrodes and Accessory Connection

If the reported event involved disposable therapy electrodes, check the removed or equivalent setup when available.

Verify:

Expected: The complete external therapy path is intact.

If a damaged, expired, poorly connected, or suspect disposable accessory is identified, replace it with an appropriate known-good accessory and proceed to controlled testing.

6. Check for a Leads-Off or Abnormal Impedance Condition

Review the reported event for:

Stryker’s LIFEPAK 35 performance inspection documentation includes patient-impedance testing and verification of PADDLES LEADS OFF behavior, supporting the importance of the external therapy connection and simulated impedance path during evaluation.

Expected: The device recognizes an appropriate connected therapy load without intermittent leads-off behavior.

If connection status changes when the cable is gently repositioned, suspect an intermittent cable or connector problem and remove the affected accessory or device from service.

7. Swap the External Therapy Cable When Available

Using only an approved, compatible known-good therapy cable:

Expected: A known-good cable eliminates an external cable variable.

If the failure disappears: Quarantine the suspect cable and document the finding.

If the failure remains: Continue troubleshooting.

Do not repeatedly flex or manipulate a questionable cable in an attempt to make a defibrillator pass.

8. Verify the Reported Operating Mode

Confirm whether the event occurred during:

Verify that the unit enters the intended mode normally and that no configuration or mode-selection issue explains the report.

Stryker provides LIFEPAK 35-specific training resources for manual mode and synchronized cardioversion, indicating these are distinct therapy workflows that should be differentiated when investigating a failed shock report.

Expected: The failure is evaluated in the same therapy mode in which it was reported.

If the issue is isolated to one therapy mode, do not assume the entire device is normal because another mode appears functional. Escalate the mode-specific failure.

9. For Synchronized Cardioversion Reports, Verify Synchronization Conditions

If the reported failure occurred in synchronized mode, verify externally that:

Expected: The distinction between a shock-generation failure and a synchronization-related inhibit condition is established.

If synchronization markers are absent or unstable despite a known-good ECG test source and appropriate external setup, stop and escalate.

10. Perform a Controlled Defibrillator Analyzer Test

Only after external inspection and with the unit removed from patient use, connect the LIFEPAK 35 to an appropriate calibrated defibrillator analyzer using approved accessories and your organization’s authorized test process.

Verify at representative energy settings as appropriate:

Stryker publishes dedicated LIFEPAK 35 Performance Inspection and Test/Calibration procedures; testing should follow the applicable authorized procedure and current service documentation rather than improvised acceptance limits.

Expected: Repeatable charge and discharge into the analyzer with acceptable measured performance.

If the device fails to discharge, delivers inconsistently, unexpectedly disarms, resets, or measures outside applicable acceptance criteria, stop testing and remove it from service.

11. Recheck With Known-Good External Components

When safe and available, repeat the controlled test using known-good:

Change one variable at a time.

Expected: The failure either follows an external component or remains with the LIFEPAK 35.

Failure follows accessory: Quarantine the failed accessory.

Failure remains with device: Escalate the LIFEPAK 35 for repair.

Failure cannot be reproduced after a clinically reported missed shock: Do not automatically close as “no problem found.” Review event details and follow institutional risk and escalation practices.

12. Stop Before Internal Therapy-System Disassembly

Do not proceed into high-voltage circuitry, internal therapy assemblies, energy-storage components, or board-level repair as part of routine external troubleshooting.

The LIFEPAK 35 has dedicated manufacturer service documentation, performance inspection procedures, and test/calibration procedures for qualified service activity.

Expected: Internal therapy faults are handled through an authorized repair pathway with appropriate procedures and test equipment.

If the Problem Persists

If power, therapy connections, approved accessories, electrode path, operating mode, synchronization conditions when applicable, and known-good external components have been checked, common external causes have been ruled out.

The issue may involve an internal therapy-control, charge, discharge, detection, connector, or related subsystem fault.

The device should be:

A defibrillator with an unresolved report of failure to deliver therapy should not be returned to clinical use simply because the symptom is intermittent or cannot be immediately reproduced.

Knowing when to stop is proper troubleshooting.

Clinical Use Tip

Never troubleshoot a suspected shock-delivery failure while the LIFEPAK 35 is being relied upon for an active patient.

Move the patient to another verified defibrillator first. Perform shock-delivery testing only in a controlled environment with appropriate approved accessories and a defibrillator analyzer.

Work Order Documentation (CCR Method)

CCR = Complaint, Cause, Resolution

Complaint

What was reported by the clinical staff.

Example:
"Clinical staff reported that the Stryker LIFEPAK 35 charged for defibrillation but did not deliver the requested shock."

Cause

What was observed during troubleshooting.

Example:
"Inspection found an intermittent therapy cable connection that produced inconsistent therapy-path recognition during controlled analyzer testing."

Resolution

What action was taken.

Example:
"Removed the defective therapy cable from service, installed a known-good compatible cable, and verified repeatable charge and shock delivery using a defibrillator analyzer before final disposition."

Helpful Details to Include (If Known)

Final Thought

A missed shock report requires a patient-safety-first response and a disciplined distinction between external connection problems, operating conditions, and true internal therapy failure. Check the simple and verifiable causes first, reproduce only under controlled conditions, escalate unresolved failures appropriately, and document exactly what was reported, found, and done.

That is successful troubleshooting.

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