MSD Project 13022

MSD PROJECT 13022VAD BREAKAWAY POWER

System Level Design ReviewJoe Tartakoff Customer/Graduate Consultant [email protected]

Matthew Myers ISE Project Leader [email protected]

Nick Dominesey ME Lead Engineer [email protected]

Jason Inman EE Team Member [email protected]

Chris Smith ME Team Member [email protected]

Ellie Sanford ME Team Member [email protected]

Michael Edson EE Team Member [email protected]

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Agenda1. Project Overview2. Customer Needs and Engineering

Specifications3. Chosen Concept4. Block Diagram5. Feasibility Analysis6. Testing Plan7. Work Breakdown Structure8. System Design Proposal9. Bill of Materials

MSD Project 13022: Breakaway VAD 2

Detailed Design Review 2/8/2013

Project Background 6-10% of all people worldwide over the

age of 65 will develop heart failure. There are 287,000 deaths per year due to

heart failure in the US. The Thoratec Heartmate II Left Ventricular

Assist Device (LVAD) is a bridge-to-transplant device that assists the heart, pumping blood throughout the body for those who are awaiting a heart transplant.



Present LVAD External Power

http://www.thoratec.com/MSD Project 13022: Breakaway VAD 4


http://www.thoratec.com/

Project Summary The transcutaneous power cord that

connects the implanted device to the external motor control unit is often a source of infection.

The cord is only about 1 foot long so it doesn’t catch on things.

When the unit is dropped, the skin around the cord tears and becomes infected.



Project Objectives Create a breakaway port for power cable that

will detach with a certain amount of force. Cable port is implanted where the cable leaves the

bodyIncrease flexibility of cable and reduce stress on

surrounding skin Create an internal power supply and motor

control unit for the pump when the cord becomes disconnected. Backup power should last long enough for the

patient to seek assistance if something goes wrong



Customer NeedsImportance: 3=high,2=medium,1=low



Engineering Specs



Needs and Specs




Notes Is CN2 a redundant statement of CN1 and therefore

unnecessary? Wouldn’t a reduction of inflammation be accomplished by reduced the force on the port?

CN5 is something that we may not be able to test or implement. Therefore, is it necessary?

CN10 sounds like something that’s left up to the surgeons. We can’t really test or implement this in a practical manner…

CN12 is being removed because it is not our concern. We will assume that there is no fluid or that there are existing methods that can be implemented to solve the situation.

S11 may be removed because it may be completely unnecessary and we can’t test for it.

S2 is may not be considered a concern due to physical observations of the current cord.


Chosen Concept



Note: One of the electrical methods has changed. I believe it is under “Manage Switchover” > “Pump Control Switchover” > changed to “External to Internal Relay”

Block Diagram



Note: Some of the numbers of wires have been reduced.


Specs vs Subcomponents


Force Pull Test on SkinAngle of

Disconnect Force (N) Displacement of skin (mm) Feeling Assessment Comments

90 degrees

1 1 light 2 5 medium

2.5 10 med-heavy 3 10 heavy

3.5 12 too heavy 4 15 too heavy

45 degrees

1 - light

2 - light-med. reasonable disconnect

3 - medium upper limit4 - med-heavy 5 - heavy

0 degrees

1 - very light barely feel it

2 - light reasonable disconnect

3 - medium upper limit4 - med-heavy 5 - heavy



Explain why upper and lower limits, and angle were chosen.


Heat Analysis - Assumptions Body Temperature (Environment) is 37˚C Heat distribution on outside of device will

be modeled via FEA Heat transfer method inside body is

conduction All energy inefficiencies result in heat

generation Device is surrounded my muscle tissue

which is at equilibrium between perfusion and heat generation



Heat Analysis – Additional 1D Assumptions 1 dimension normal to the skin Uniform heat generation Constant Properties Body is at equilibrium (neglect heat

generation effects) Steady State



Heat Analysis - Data Reference Temperatures[C]: Body Temp= 37 C Ambient Air Temp= 25 C

Conduction Coefficients : Internal Organs and Muscle = 0.500 W/m*K Skin and Fat=0.300 W/m*K Titanium=19.000 W/m*K (P13022 only) Clothing=0.029 W/m*K

Convection Coefficients [W/m*K]: Air=10.000



Heat Analysis – Critical ValuesThe purpose of our thermal model is to

ensure this device will not harm the patient.

With a factor of safety of 2, our maximum heat flux through the tissue is 40mW/cm2



Heat Analysis – 1D Analysis ModelDetailed Design Review 2/8/2013


Heat Analysis - Results

25 30 35 40 45 50 550

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5Heat Generation vs. Device Temperature at Contact

Hea

t Ene

rgy,

q (W

)

Temperature, T (C)

Q/Tair CurveHeat Dissipated to AirQ/Tbody CurveHeat Dissipated to BodyTotal Heat Dissipation

25 30 35 40 45 50 550

1

2

3

4

5

6

7

8Heat Flux vs. Device Temperature at Contact

Hea

t Ene

rgy,

q (m

W/c

m2)

Temperature, T (C)

Q/Tair CurveHeat Flux Dissipated to AirQ/Tbody CurveHeat Flux Dissipated to BodyTotal Heat Flux Dissipation -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04

20

25

30

35

40

45Temperature Distribution

Distance across device, [m]

Tempe

rature [C

]

q=0.0Wq=0.1Wq=0.2Wq=0.3Wq=0.4Wq=0.5W



Heat Analysis – Engineering Model

Conduction

Internal Environment(Abdomen Muscle)

Device

Boundary Temp: 37˚C

•The Device will be implanted in abdomen muscle•Assuming a worst case scenario, the device will be surrounded by muscle tissue in all directions for an “infinite” thickness.•An ANSYS model which includes the boundary temperature of 37˚C and all muscle properties will show worst case temperature and flux conditions



Heat Analysis - Summary For the given area of 64cm2 , 0.3 W

(4.67mW/cm2) of heat generation will be dissipated before exceeding 40oC.

For a surface area of 340cm2 we should be allowed to generate up to 13.6 W of heat energy within the device.

Expected worst case heat generation = 2 W.



Heat Analysis - Conclusion The Internal Battery Storage Device is not likely to

harm the body through heat generation based upon the of energy flux through the total surface area.

Further analysis will be conducted (in ANSYS) to confirm the results.

Due to the extreme difficulty of finding a relatively accurate model for the body in relation to the LVAD system, the 1-D analysis is only useful for worst case results and only provide limited useful data.

Further analysis in ANSYS should provide more reliable results.

Development of the P13022 device should continue with minimal design change.



Testing PlanDetailed Design Review 2/8/2013


Work Breakdown Structure



System Model Detailed Design Review 2/8/2013

System Model (sketch)


Existing Batteries

Breakaway Port

External Signal

Controller

Internal Pump(Thoratec Heartmate 2)

Internal Signal Controller & Batteries

External Pump Monitor


Internal Power Control (sketch)



Breakaway Port Design




Bill of MaterialsMaterial: Quantity: Price per unit: Total cost: Comments:

Batteries 8 $3.50 $28.00

LiFePO4 18650 Rechargeable Cell: 3.2V 1500 mAh, 4.5A Rate, 4.32Wh, UL Listed, UN Approved (NDGR) Part Number: LFP-

18650-1500

Polycarbonate/Acrylic 1 $0.00 $0.00 Old scrap piece will be used unless more models needs to be made.

motor controller design board 1 $300.00 $300.00 used to design the motor controller

Bio-compatable titanuim roundstock 1 $23.10 $23.10

For implant 1.25"D X 1.00"L http://www.onlinemetals.com/merchant.cfm?pid=6776&step=4&showunits=inches&id=18

7&top_cat=0

Recharge Board 1 $6.45 $6.45PCB (Protection circuit module) for 4 cells (12.8V) LiFePO4 Battery Part Number:

PCB-LFP12.8V2A

Surgical tubing 1 $30.39 $30.39 http://www.amazon.com/Latex-Rubber-Surgical-Tubing-39323932/dp/B0045V36PQ



Bill of Materials (cont’d)Material: Quantity: Price per unit: Total cost: Comments:

Wire 1 $13.15 $13.15 100ft, 16 gauge wire

Magnets 5 $1.00 $5.00

Microcontroller 2 $20.00 $40.00

Relay 1 $17.19 $17.19

Resistors $0.00

Capacitors $0.00

Thermocouple $0.00

Connectors $0.00

PBC board 1 $50.00 $50.00

Vibrating motor 2 $3.99 $7.98 28821-nd

10-pin connector $0.00

Total: $463.28


System Model (sketch)

Hanzlik in 20 years.


I love my new breakaway

port system!


MSD Project 13022

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