• Neuromuscular blockade (NMB) monitoring —> Used with anesthesia & sedation in critically ill patients

  • NMB monitoring devices are expensive

  • Prototype based on open-source hardware & software

  • On-line peak detection

  • Preliminary measurements in a healthy subject

Neuromuscular Blockade Monitoring

  • ICU patients often need mechanical ventilation

  • Why using Neuromuscular Blocking Agents (NMBAs)?

  • They prevent muscle contractions and can improve tolerance and comfort

  • Controlled doses increase chest compliance, improve oxygenation, reduce postoperative respiratory complications (PRC)

  • Why NMB monitoring? Too little: residual paralysis. Too much: risk of PRC

  • But careful: Qualitative assessment is unreliable —> Need quantitative NMB monitoring

Train-of-Four (ToF)

  • Transcutaneous electrical stimulation applied to (ulnar) nerve —> measure muscle contraction (accelerometer)

  • Four stimuli @ 2 Hz

  • ToF Count: # of detected responses

  • ToF Ratio: 4th to 1st response T4/T1

  • ToF delivered at 15–20 s intervals to prevent potentiation

Commercially Available ToF Devices

  • Need of Low-Cost Devices


Design & implement a low-cost NMB monitoring device that may help reduce the economic burden of health-care institutions in low- and middle-income countries

Prototype Overview

  • Arduino

  • ADXL345 accelerometer

  • TENS 3000 unit

  • Relay

  • LCD

Peak Detection Algorithm

  • Normalized (z-score) signal over a time window

  • Peak if exceeds a threshold

  • Lag: window size

  • Influence: weight [0-1] of past points

Adjusting Peak Detection Algorithm


  • Inexpensive, modular, simple-to-build, open-source NMB monitoring device, able to display ToF Count & ToF Ratio

  • Preliminary measurements showed great promise to transition into higher developing stages

  • Exhaustive assessment needed to ensure safety and effectiveness in clinical settings