ST-504 use guide
What does session duration mean on the ST-504?
Read the timer as an equipment boundary, not a personal treatment prescription.
Record the timer
Keep mode, pressure, heat, and duration together.
Compare fairly
Hold position and fit steady.
Stop when needed
A timer never overrides a warning sign.
Session duration is a controller setting. It tells the device how long the programmed cycle is intended to run. It does not tell a reader how long they should use compression for a medical condition.
Read the timer with the selected program
Record the mode, pressure, heat, vibration, and duration together. A session that ends at the documented time is different from a session that stops during inflation. The first may be normal timer behavior. The second may require a battery, connection, or troubleshooting check.
Use the complete guide for the product control map. Use the troubleshooting guide when the controller stops unexpectedly or will not complete a cycle.
Keep the comparison fair
If you are observing comfort across sessions, keep the position, sleeve fit, clothing, and other controls similar. Do not extend a session simply because the sensation seems mild. Do not shorten or lengthen a session to test a new symptom.
An equipment note can say, “The cycle ended at the displayed duration.” It cannot say that the duration treated swelling or guaranteed recovery.
A timer note should include the reason for stopping
Record whether the session ended normally, reached the displayed duration, stopped after a warning, or stopped because the user chose to pause. Add the selected mode and the device state. This keeps a timer question separate from a symptom question.
Stop conditions remain more important than the timer
Stop for pain, increasing numbness, skin change, unusual heat, visible damage, smoke, or unexpected operation. A remaining timer does not require the user to continue. The user must be able to stop without pulling the sleeve or cable.
The current instruction for use controls the exact duration options. A timer is a product boundary, not a personal prescription.
If a reader wants a longer session because the first one felt uneventful, that is not a reason to extend the timer without checking the manual. If discomfort appears, the stop action takes priority. The useful record is what the controller did and why the session ended. Note the date, selected program, battery state, sleeve position, and room conditions too.
This record also helps when two sessions seem different. A changed room, clothing layer, battery state, or sleeve position can alter the experience without changing the timer. Keep those factors visible before treating duration as the explanation.
Source boundary for timer questions
Use the current instruction for use for the available durations. General FDA medical device information cannot turn a timer into an individual treatment recommendation.