Download Final Poster - Research

Software-driven Pneumatic Beating Heart
Simulator and ECG Display
Jacob Bauer, Nicole Rice, Ashley Whiteside
Advisor: Dr. Jonathan Nesbitt
Vanderbilt University School of Engineering
Vanderbilt Medical Center
Vanderbilt Medical Center, Vanderbilt University, Nashville, TN
Introduction
Design Components
• Currently, surgical residents train on unrealistic models or
cadavers. These do not accurately simulate an operating
environment or adequately prepare a students for work on
live patients.
Software: Primary Components
• The Beating Heart simulator would provide an essential
bridge in training between cadavers and participating in live
surgery for surgical residents.
• Likewise, the Simulator can be used by a surgeon at any
level of experience to practice a procedure before
performing it on a patient.
Prototype
• The computer interface consists of a simple Graphical User Interface (GUI)
which allows for the user to input a heart rate and arrhythmia value.
• Pump Driver
• Outputs signal to pump via Arduino board
• Simulator
• Singleton object which stores variables and handles their access
• ECG_display
• Builds and updates ECG display
Software: Pump Driver
• The heart rate value is used
to transmit a timed signal to
the Arduino Uno
microcontroller.
• This could be very helpful in situations where a doctor must
perform an unfamiliar procedure or one that he/she does not
do on a regular basis
Question and Thesis
• The microcontroller then
produces a 5 VDC voltage
signal which is used to control
the physical heart beat.
• Can a user interface be created on a computer that can link
and affect different aspects of a heart simulator?
• The user will input a heart rate. This input will then cause a
sample heart to beat at that rate and simulate an ECG that
will display the blood pressure and heart rate.
• The point of this simulation is to mimic real problems that
may be observed in the operating room and train students to
react accordingly.
Previous System
Previous System in use by Dr. Nesbitt:
• Utilized a windshield wiper motor to cyclically pump a plastic
bellows.
• The bellows forced air
through surgical tubing
connected to party balloons
placed in right and left
ventricles of a porcine heart.
Project Cost
Figure 2: Overall Program Code Diagram
Software: ECG
Figure 3: GUI Window
Our system is able to plot the ECGs of the
following arrhythmias and heart-rates
•
•
•
•
Normal Sinus Rhythm: 50-130 bpm
Atrial Fibrillation: 100-150 bpm
Ventricular Tachycardia: 80-130 bpm
Ventricular Fibrillation: no rate range
• The program also generates a scrolling ECG plot
corresponding to the desired heart rate and
arrhythmia provided by the user.
• The ECG is plotted in a separate window allowing
the surgeons undergoing training to monitor the
ECG during the operation.
Figure 4: ECG Code Diagram
Figure 5: ECG Display
• Did not produce a simulated
ECG display
Hardware
Figure 1: Current System
Engineering Requirements
• We used a three-way solenoid valve to regulate the flow of compressed air into balloons placed in the right and left
ventricles of the porcine heart, as shown below in Figure 5..
• The pneumatic inputs to the valve were connected to the in-wall 20 psi compressed
air and vacuum sources in the simulation laboratory. The output was connected to
our two balloons via y-connected pneumatic tubing.
• The simulator must be controlled by a computer software
package.
• The software must drive a physical heartbeat in a porcine
heart based on the user provided heart rate data.
• The software must also produce an ECG display that
corresponds to the user provided data.
• The simulated heartbeat must be dynamically alterable
• The physical palpitation of the porcine heart must mimic
real-life motion.
• A porcine heart is being used because it is the most
anatomically similar organ to humans among different
animal test subjects.
Dr. Nesbitt had allotted approximately $2,000 for the project;
however we needed only a fraction of this budget.
Part
Transistors
Price
$14.57
Solenoid Valve
Pneumatic Fittings
Arduino Uno
Power Adapter
Total Estimated Cost
$18.84
$31.44
$29.95
$14.99
$109.79
Conclusions
• Did not allow for variable
BPM or real time control
• Did not displace enough air
to replicate the contraction
of a healthy heart.
Figure 8: Completed Prototype
Figure 6: Solenoid Valve Setup
• We created a computer-driven system that simulates the
beating of a human heart and a corresponding ECG to be
used in the training of cardiothoracic surgery and perfusion
students by the Vanderbilt University School of Medicine.
• Our system will be a key component of the cardiac surgery
training program at Vanderbilt and will be used to train at
least six cardiothoracic surgery residents and three
perfusion students per year as well as additional residents in
anesthesia and general surgery.
• Our system allows the users significantly more control over
the simulation than their current system permits, enabling
the system to be used to simulate multiple different
situations.
• Our valve is triggered by a 12 VDC so in order to control it via the Arduino we
constructed a transistor circuit to act as a switch between the valve and an external
power source.
• Our prototype will provide these students with a realistic
surgical training environment, better preparing them to
perform surgery on actual patients.
• When the heart is to expand the Arduino’s output pin is set to ‘high’, creating a 5 V
difference in potential between that pin and the Arduino’s ground.
• This output is connected to the gate of a
logic-level NMOS transistor while the valve is
connected to a 12 VDC wall wart across the
transistors source and drain.
• Very few programs have access to a simulator as versatile
and capable as the one we have created. The creation of
this model will be an asset to Vanderbilt’s cardiothoracic
surgery program enabling it to continue to be a leader in its
field.
• The transistor circuit allows current to flow from the wall wart through the solenoid,
triggering the valve when the Arduino’s output is ‘high’ and prevents current from
flowing when the output is ‘low’ thus switching the valve in accordance with the
Arduino’s signal.
Figure 7: Transistor Schematic
Acknowledgements
We would like to thank everyone who contributed to this
project, particularly the following: Jonathan C. Nesbitt, M.D.,
Phillip Williams, B.S., Paul H. King, Ph.D., P.E., Robert J.
Barnett, Ph. D., Covidien, Vanderbilt Medical Center