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What This Guide Helps With
Poor signal quality or absent pleth waveform caused by motion, placement, perfusion, sensor damage, cable problems, or display configuration.
Step-by-Step Troubleshooting
1. Protect the Patient and Maintain Monitoring
Do not continue using unreliable monitoring while a patient depends on it. Move the patient to another verified monitor or establish an appropriate alternate monitoring method before troubleshooting.
Expected outcome: Patient monitoring remains continuous during evaluation.
2. Confirm the Signal Problem
Observe whether Signal IQ is consistently poor, the pleth waveform is missing, or both conditions occur together.
Determine whether numerical values are present, unstable, delayed, or absent. Confirm whether the issue affects one patient, one sensor, or every setup.
Expected outcome: The reported condition is reproduced and clearly defined.
3. Check the Sensor Site and Perfusion
Inspect the site for cold skin, low perfusion, edema, excessive pressure, nail coverings, poor contact, or placement on an extremity affected by a blood pressure cuff.
Use a clinically appropriate alternate site when authorized.
Expected outcome: Signal IQ improves and a stable pleth waveform appears. If it remains stable, troubleshooting can stop.
4. Correct Sensor Placement
Verify that the sensor is properly aligned, fully seated, and secure without being overly tight.
Ensure the optical components face each other correctly and are not obstructed by contamination, adhesive folds, or damaged material.
Expected outcome: A consistent waveform and signal quality indication are restored. If so, troubleshooting can stop.
5. Minimize Motion and Cable Strain
Stabilize the extremity and route the patient cable to prevent pulling, swinging, or repeated movement at the sensor.
Check for tremor, shivering, transport vibration, or nearby equipment contacting the cable.
Expected outcome: Signal quality becomes stable when motion and cable strain are reduced.
6. Check Display and Waveform Configuration
Verify that the pleth waveform is enabled and visible in the active display layout or profile.
Do not change clinical alarm limits or protected configuration settings without authorization. Compare the display with another Rad-97 using the same approved profile when available.
Expected outcome: The waveform is visible when enabled and configured correctly. If this resolves the issue, troubleshooting can stop.
7. Inspect All External Accessories
Inspect the sensor, patient cable, adapter, and monitor connection for damage, contamination, bent contacts, loose fit, or worn strain relief.
Reconnect all accessible connections securely.
Expected outcome: The signal remains stable without moving or holding the cable.
8. Test With Known-Good Accessories
Substitute a compatible known-good sensor and patient cable. Test the suspect accessories on another verified compatible device when appropriate.
Expected outcome: The problem follows a failed accessory or remains with the Rad-97. Replace the defective external accessory if identified.
9. Test Under Controlled Conditions
Remove the device from patient care and test it with an approved simulator or suitable controlled test subject.
Observe Signal IQ, pleth waveform, pulse rate, saturation response, and stability.
Expected outcome: The device produces a stable waveform and normal signal indication under controlled conditions.
10. Complete Functional Verification or Escalate
Verify waveform display, sensor detection, alarm response, and stable operation after correction.
If poor Signal IQ or a missing waveform continues with known-good accessories and controlled testing, remove the unit from service.
Expected outcome: The device either passes final verification or is routed for bench evaluation.
If the Problem Persists
External causes involving patient site, perfusion, motion, sensor alignment, accessory damage, and display configuration have been ruled out.
The remaining cause may involve the sensor input connector, signal-processing system, display software, profile configuration, or another internal service-level condition. Remove the Rad-97 from service, label it Out of Service, and send it for qualified repair or bench evaluation using current manufacturer documentation and approved test equipment.
Do not perform unauthorized service-menu changes or internal board-level repair. Complete functional, waveform, and alarm verification before return to service.
Clinical Use Tip
A displayed saturation value without a reliable pleth waveform should be interpreted cautiously until signal quality and the complete monitoring setup are verified.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Clinical staff reported poor Signal IQ and no visible pleth waveform during pulse oximetry monitoring."
Cause
What was observed during troubleshooting.
Example:
"Clinical Engineering found a damaged patient cable that produced an unstable signal when flexed near the connector."
Resolution
What action was taken.
Example:
"Replaced the patient cable with a compatible approved cable, confirmed stable Signal IQ and pleth waveform, verified alarms, and returned the monitor to service."
Helpful Details to Include (If Known)
- Signal IQ indication
- Pleth waveform status
- Numerical reading behavior
- Sensor site and perfusion condition
- Patient movement or vibration
- Sensor and cable condition
- Display profile or waveform setting
- Known-good accessory results
- Simulator results
- Final alarm and functional test results
Final Thought
Maintain patient monitoring, verify signal quality from the patient outward, rule out placement and accessory problems before internal failure, and document the confirmed correction and final test results.
That is successful troubleshooting.