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R&D Robotics Engineer · New Technologies Research Center, Amirkabir University · 2021–2022

Blood flow restriction training device

A medical device prototype, from circuit to app.

The problem

Blood flow restriction training only works safely when cuff pressure is set for each person, from their own limb occlusion pressure, rather than one fixed value.

What I did

  • Cuff inflation mechanism and mechanical frame
  • Analog circuits and pressure-signal processing to estimate limb occlusion pressure
  • STM32 and ESP32 firmware
  • Desktop control application

Results

A working prototype, built in a small team, that measures each user's limb occlusion pressure and sets the cuff pressure from it. It runs from its own touchscreen or from a desktop app.

The BFR device: control box with touchscreen between two limb cuffs
The finished device with its two limb cuffs.
Inside the control box: circuit boards, pump, valves and tubing
Inside the control box: electronics, pump and valves.
Early prototype with cuff, pressure gauge, controller box and power supply
An earlier prototype on the bench.
Device touchscreen showing pressure, percentage and limb occlusion pressure
The device screen: cuff pressure, target percentage and the measured limb occlusion pressure.
Desktop control application
The desktop control app.

Signal processing

The limb occlusion pressure is estimated from the cuff pressure as it deflates. The raw signal is filtered, then the small pulses riding on it are separated out.

Raw cuff pressure signal during deflation
Raw cuff pressure.
Cuff pressure after a 40 Hz low-pass filter
After a low-pass filter.
High-pass filtered oscillometric pulses
After a high-pass filter: the pulse oscillations used for the estimate.