Objective: To develop a system that transmits signals to and from a Left Ventricular Assist Device (LVAD) with a decreased amount of physical wiring through the skin.

Motivation: The RIT LVAD blood pump used a large signal and power cable entering through the skin. The lack of flexibility in this cable caused discomfort, limited range of motion, and was associated with many health risks to the patient because of the exposure of the tissue to the cable, which caused approximately 40% of LVAD patient fatalities.

In order to power the LVAD system located inside the body four percutaneous 26AWG wires are required.

A TET system was designed to eliminate this required connection. Using inductive coupling, a primary coil located on the outside of the body ideally would transfer the required energy to a secondary coil located inside the body. Efficiency of the TET was measured over the coil at varying air gap distances. Power efficiency was between 15-30% at 0.5 cm spacing and between 4-6% at 2 cm.

DESIGN IMPROVEMENT: The cable was decreased to a diameter of 2.7 mm with only 7 wires. This provided a 300% decrease in diameter and a 370% improvement in flexibility. The reduced diameter was accomplished by changing the placement of electronic components as well as implementing Serial Peripheral Interface (SPI) protocol. This method was capable of transferring all of the required sensor and control signals over fewer wires.

ORIGINAL DESIGN: The original design of the percutaneous LVAD cable consisted of 23 wires with a diameter of 8mm.

TRANSCUTANEOUS ENERGY TRANSFER SYSTEM (TETS)

Project: 10022Dates: 09/02/2009 – 02/20/2010Advisor: Dr. Rick Lux Funding: National Heart, Lung and Blood Institute (NIH)

CONCEPT AND DESIGN

Old Cable: Diameter = 8 mm

• Flexibility: The cable was tested for flexibility measuring its deflection under various weights, applied to the center of a cable section.

• Power cable: The cable’s current capabilities were tested using a load resistance to ensure it could safely carry 3 Amps over a sustained period of time.

• Shock: The cases were drop tested for their ability to protect electronics from mechanical shock in case of impact

• Signals: The integrity of SPI was tested to ensure continuity of signal processing of PWM and HESA sensors by measuring the input signal in comparison to the output signal

TESTING

TRANSCUTANEOUS SIGNAL AND POWER TRANSMISSION FOR VENTRICULAR ASSIST DEVICE

Pulse Generator

H-BridgeRectifier

Voltage Regulator

Powered LED

Primary CoilSecondary Coil

Carl Hoge (ME)Sara Carr (EE)Lead Engineer

Robert MacGregor (ISE)

New Cable: Diameter = 2.7 mm

Interior ElectronicsExterior Electronics

ORIGINAL DESIGN

Interior ElectronicsExterior Electronics

PROPOSED DESIGN

TETS

Customer Needs Importance Description Test Results & Future Work

1 4 The cable entering the body is more flexible. Improvement of 370% over the old cable

2 5 The cable entering the body is smaller in diameter. Cable diameter: 2.7 mm (300% decrease)

3 - 5 5Eliminate as many wires as possible from XPC Control Target to the LVAD, position sensors, and Active Magnetic Bearings

15 wires eliminated using SPI protocol7 wires remain

6, 8 3Wireless Power System to eliminate power wires (15V and

Ground) through the human skin and biological tissues.The TET system demonstrates feasibility of eliminating the 4 power wires

by delivering power with 15 – 30% efficiency.

9 , 10, 14 5The cable, packaging, and connections are safe to human

tissue.

The cable and case are covered by medical grade LOCTITE 5248™ silicone. All components and materials are IEEE and FDA approved, as

applicable.

11 5Heat generated by the inner transceiver does not cause tissue

damage.Heat test will verify that the surface temperature of the case does not

exceed 50ºC.

12 5 The heat created by a body does not damage the electronics.Heat test will verify that the ambient temperature of electronics does not

exceed 120ºC.

13 5Inner and outer transceivers must be protected from the

outside forces. A drop test proved durability of the case and proper protection of

electronics.

15 - 18 5The device must function continuously, without user

intervention, and be reliable with the currently established system components.

Input and output of PCB signals were tested using wave generator and oscilloscope. It will be tested with the current LVAD system in order to

demonstrate these functions.

20 5 The interior transceiver must fit within the human chest cavity.Available cavity volume: 650 cm3

Inner case volume: 90 cm3

21, 22 5The exterior transceiver must be small and light enough to

wear on a belt.Inner case: 9 x 5 x 2 cm, 125g

Outer case: 11 x 3.5 x 2 cm, 125gImportance scale (5=must have, 3=nice to have, 1=preference only).

RESULTS & CONCLUSIONS

CONCEPT SELECTION: Wireless communication was considered, but due to the time frame and complexity of the human body, a hardwired design was chosen.

Oxana Petritchenko (ME)Project Manager

Keith Lesser (CE)

Heat Shrink Boots

Power Cable

Outside case

DisplayPort Connector

Signal cable(Through Skin)

Inner Case PIC

VoltageDividers

VoltageRegulator

Relay Switch

Inner Case

Grommets

PIC DAC

Outer Case

SYSTEM PROTOTYPE

Dr. Steven DayFaculty Guide

Dr. Cheng ShanbaoCustomer