ST-504 safety guide
What should a user do when numbness appears?
New or increasing numbness is a stop signal, not a reason to test a stronger setting.
Stop first
Pause the session and remove the pressure question.
Record the event
Note time, mode, pressure, fit, and skin.
Escalate appropriately
Professional guidance may be needed.
Stop the session when numbness appears, increases, or feels unusual. Numbness can have many causes. A product page cannot determine whether it came from fit, pressure, a health condition, or another factor.
Do not restart to reproduce it
Do not increase pressure. Do not add heat or vibration. Do not change several controls and try again. Remove the equipment question from the immediate decision and assess the person’s condition through the appropriate professional route.
The pressure comfort guide explains how to describe a device sensation. The safety guide explains when suitability and stop conditions take priority.
Make the record concrete
Write down the selected mode, pressure label, heat and vibration state, sleeve position, session duration, and the time numbness began. Note visible skin changes and whether sensation returned after stopping. Do not label the cause in the record.
If the controller also shows a fault, use the troubleshooting guide for the equipment portion. It cannot decide whether numbness is safe to ignore.
Why the time of onset matters
Numbness that was present before use, numbness that appears after a sleeve shifts, and numbness that continues after stopping are different observations. None should be interpreted from a product label alone. Keep the timeline and bring it to the relevant professional if the change persists or is concerning.
General FDA medical device information provides context, not individual medical advice.
Do not let the absence of visible skin change reassure you when sensation is changing. Skin appearance and sensation are different observations. Keep the person seated, keep the device off, and record whether sensation returns after stopping. If the change remains, worsens, or is accompanied by pain or weakness, use the appropriate professional route promptly.
The useful order is simple. Stop. Check the skin. Record the controls. Ask for guidance when the change persists. Do not restart to see whether the same numbness returns.
If another person is supervising, tell them immediately. Do not continue alone when the user cannot reliably describe the sensation.
The supervisor should help stop the device, record the event, and seek guidance rather than change controls.
The supervisor should not choose a stronger control on the user’s behalf. Their role is to help stop, record, and seek the appropriate next step.