A Closed Loop Multi-Site Gastrointestinal Pacing System

1
A Closed Loop Multi-Site Gastrointestinal Pacing
System
Jim Simpson, and Frank Myers
www.ncbionics.org
Faculty Advisor Dr. Maysam Ghovanloo
Electrical and Computer Engineering, North
Carolina State University, Raleigh, NC
1. BACKGROUND
4. EXPERIMENTAL RESULTS

• Organs of the Gastrointestinal (GI) system have
  natural pacemakers
• This pacing controls the contractions and hence
  the motility of the stomach
• The smooth muscles of the stomach are coordinated
  by myoelectrical activity (slow wave)
• The frequency of slow wave is around 3 cycles/min
  in humans
• External stimulation can be applied to support or
  change the natural pacing

• The system was used to record slow waves from a
  dog at different locations in the stomach

2. MOTIVATION
Slow wave recorded from 8cm and 12cm above the
pylorus

• Studies have shown that a closed loop system is
  capable of treating motility disorders (gastro
  paresis) by increasing, decreasing or following
  the natural pace of the stomach
• Existing stimulators are open looped and reduce
  the symptoms like nausea and vomiting at best
• Promising treatment for morbid obesity by
  reducing the desire for food intake as well as
  reducing the absorption of food by the GI tract.

• Biphasic capacitive discharge across a mouse
  somatosensory cortex tissue slice

10 nF Capacitive, 10 ms discharge, 50 pulses at
50 Hz, Q ? 40 nC
5. FUTURE WORK
3. INTERFACE IMPLEMENTATION

• Phase 2 of the project involves implementing the
  integrated design for the recorder and stimulator
• The signal processing and control algorithms will
  be further developed

• Recorder
• Adjustable gain As high as 1000000
• 0.05Hz High Pass Filter
• 35Hz Low Pass Filter
• Sampling rate ? 1kSaps max
• ADC on chip the Atmel Atmega32 AVR microcontroller

• Wireless
• Implemented using LAIPAC TRF-2.4G wireless
  transceiver
• 2.4 2.524GHz ISM Band RF
• 125m LOS range
• 1Mbps data rate
• 125 programmable channels with up to 240 devices
  (addresses) per channel

• USB
• Implemented using Cypress CY7C68013 EZ-USB FX2
  microcontroller
• Supports USB 2.0 high-speed at 480 Mbits/s
• Low cost (15/chip) and popular hardware
• Bus powered (no need for additional supply)
• General Purpose Interface (GPIF)

• PC Software
• Custom GUI Front end capable of displaying up to
  8 channels simultaneously
• Signal processing capable of noise cancellation,
  frequency estimation and tracking
• Closed loop control capable of generating
  stimulation parameters based on signal processing

• Stimulator
• Voltage Controlled Stimulation (VCS), Current
  Controlled Stimulation (CCS) and Switched
  Capacitor Stimulation (SCS)
• Bipolar/Monopolar stimulation
• Biphasic/Monophasic stimulation
• Four stimulation sites
• 0-11V, 0-10mA stimulus level
• Digital, wireless control of stimulus parameters
• Isolated instrumentation and power circuits

6. CONCLUSION

• The system successfully demonstrates the closed
  loop link from the recorder to the stimulator
• The software is a stable research platform to
  test various control algorithms for increasing,
  decreasing or synchronized pacing based on the
  recorded signals
• The stimulator is capable of generating a variety
  of signals with real time control from the PC

Stomach
Recorder
Wireless
USB
PC Software
Stimulator
Stomach
USB
Wireless