Beating Heart Simulator: Oral Report 2 Ashley Whiteside Nicole Rice Jacob Bauer 1
Question and Thesis 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 and/or blood pressure. 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. 2
Jonathan C. Nesbitt Graduated from University of Virginia with a BA in Biology Attended the Georgetown University School of Medicine in 1981 Completed postgraduate training at Vanderbilt in 1986 Was a surgeon on the USNS Comfort during operation Desert Storm/Shield Joined department of thoracic surgery at Vanderbilt University Medical Center in 2008 Specializes in the treatment of esophageal cancer, lung cancer, thymoma and thymic carcinoma 3
Background Current System in use by Dr. Nesbitt Utilizes a bicycle pump which cyclically pumps a plastic bellows. Air lines connected to party balloons placed in right and left ventricles. Does not allow for variable BPM or real time control Does not produce a simulated ECG display Does not displace enough air to accurately represent the magnitude of contraction in a healthy heart 4
Engineering Requirements 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 reallife motion. 5
Methods We have segmented our design process into three main steps: 1. Produce a beating heart 2. Computer control of heart 3. Simultaneous ECG output 6
Developing a Beating Heart We plan on using an actuator to regulate the flow of compressed air into balloons placed in each ventricle. 7 Image courtesy of http://www.yourheartvalve.com/heartbasics/heartanatomy.htm
Developing a Beating Heart We plan on controlling the actuator with a square wave input driven by an Arduino microcontroller. At rising edges the signal will produce a digital logic 1, allowing air to flow into the balloons At falling edges the signal will produce a digital logic 0 and cut off the air supply. 8 Images by Judy Jowers from http://www.flickr.com/photos/judyjowers/4391452125/
Developing A Beating Heart We are currently looking at means of driving the movement of air into the balloons We are considering two main options A solenoid driven pneumatic control valve A servo motor driven pump or bellows system 9
Three Way Solenoid Pneumatic Control Valve Solenoid pneumatic valves are relatively cheap at around $100 and incredibly reliable. These are capable of controlling the pressure we need at rates of under 20 milliseconds. 10 Image courtesy of http://www.omega.com/ppt/pptsc.asp?ref=sv4100_sv4300&ttid=sv4100_sv4300&nav=
Three Way Solenoid Pneumatic Control Valve Air Compressor Arduino Vacuum Pump Control Valve The arduino will control the pneumatic valve to alternate between compressed air and the vacuum pump to produce the physical heartbeat. Balloon 11
Servo Motor Driven Pump Alternatively, we have considered using a servo motor to drive a piston or bellows system that will force air into the balloons This option is advantageous because it is significantly cheaper than using a pneumatic control valve. Unfortunately, the motor system is less mechanically reliable and offers less control over the movement. 12 Image courtesy of http://www.galilmc.com/products/servo-motor.php
Servo Motor Driven Pump to motor piston air balloon The motor system would work by driving a piston in a vacuum tube. As the motor rotates the piston would oscillate between forcing air into the balloons and sucking air from them, thereby eliminating the need for a vacuum system. 13
Computer Interface We will develop a computer program that will enable the user to dynamically alter the heart rate during simulated surgery. Ultimately this software will both produce the ECG display and program the Arduino microcontroller in order to control the motion of the heart. Input Heart Rate 14 Image courtesy of http://mc202.com/synthesizers/arduino-glitch-box-machinedrum/ and of http://www.yourheartvalve.com/heartbasics/heartanatomy.htm
Computer Program (C++) Pump Driver Simulator ECG Driver USB Port Classes Singleton Stores heart rate and arrhythmia values Allows for dynamic access to variables Ensures single instance of class (Singleton GoF Pattern) Pump Driver Operates within unique thread Accesses heart rate value from Simulator class Outputs instructions to pump through Arduino board ECG Driver Operates within unique thread Accesses heart rate and arrhythmia values from Simulator class Outputs instructions to EKG through Arduino board Output to ECG Output to Pump 1. Pump Driver input -> Pin 1 2. ECG Driver input -> Pin 2 Arduino Program (C++) 15
Simultaneous ECG Output We plan on recording different ECG rhythms as.wav files. Once completed, these.wav files can be freely manipulated and accessed through the use of C++. The ECG output and beating heart prototype will operate simultaneously but completely independently of one another. 16 Image from: http://www.swharden.com/blog/images/simple_ecg_circuit_output.png
Simultaneous ECG Output Currently, a program is being licensed that displays variable and adjustable ECG signals. We are considering using this program as an alternative to manipulating sample recordings of the various waveforms when displaying the ECG. 17
Additional Goals Once we have developed a successful prototype we will contemplate endowing the system with additional capabilities to increase functionality. These include: Plot of arterial pressure Simulation of the effects of anesthesia Simulation of common arrhythmias 18
Status and Results We have met with the faculty sponsor, Jonathan Nesbitt, and been informed of the details of the project. Dr. Nesbitt also showed the current heart pump. We are acquiring an ECG generating program that allows for variability. A skeleton program has been developed in C++. We are researching various types of mechanical control devices to drive the heart. Scheduled the first meeting with Dr. Nesbitt for the new year, during which we will present different potential devices and determine budgetary constraints. 19
Conclusion Our goal is to develop a prototype for a cardiac surgery simulator that will permit dynamic alteration of variables during surgery. We are planning to meet with Dr. Nesbitt consistently throughout the semester. We will be ordering raw materials within the next month and continue developing the program. 20