Artificial Heart Valve Turbulence Measurement Device Team 12: Drew Seils Shane Tornifoglio
Objectives Variable flow rate for re-circulated blood Able to put commercial heart valves in-line for testing Display clotting factor levels and flow rate Utilize minimal RBC stress pump Work with actual blood (clotting properties) Maintain homeostasis (max/min pressure, temperature)
Method of Measurement To measure turbulence the device has been designed to measure the amount of free hemoglobin in the blood, released from ruptured RBC s. For this purpose the team has employed the use of the Orsense NBM-200MP
Orsense NBM-200MP The device is a noninvasive monitoring system that measures light absorption and scattering as the beam passes through the thumb of the patient. This device can however be applied to the soft tubing used in this heart valve device. The amount of light absorbed by the erythrocytes is the indicator for hemoglobin levels.
Orsense NBM-200MP The sensor will be mounted within the artificial valve testing device and the monitor will be located externally.
Medtronic Bio-Pump Plus The blood pump chosen for this device is a centrifugal pump, which eliminates the need for rollers or impellers to push blood through a tube, minimizing RBC stress. Blood enters through the top and is circulated before exiting at the bottom.
Medtronic Bio-Console 560 Control unit for the blood pump. Controls and displays variable flow rate and pump speed at the site of the pump. The device also has two pressure gauges to determine system circulation pressure.
Medtronic Bio-Console 560
Bio-Probe Flow Transducer Measures actual flow rate of blood by its natural levels of conductivity. Located between valve and Orsense sensor It is not affected by blood turbulence, hematocrit levels, or temperature of the system.
T2T Heparin Biocompatible Tubing Tubing is designed with biocompatible surfaces for increased thromboresistance and biocompatibility. By utilizing a biocompatible surface it decreases the amount of platelet activation and RBC stress during passive flow.
Artifical Heart Valve Testing Device
Artifical Heart Valve Testing Device
Artifical Heart Valve Testing Device The housing for the device is made of aluminum and the biocompatible tubing enters from both sides connecting at the valve The valve integration system includes a small door that pinches the valve to be tested in line with the tubing
Artifical Heart Valve Testing Device The valve door pinches the valve to the housing with a rubber seal to maintain pressure during testing. The system is locked in place using a locking arm and the rigid connections shown.
Artifical Heart Valve Testing Device The biocompatible tubing connects to the valve door shown previously. It also enters through the opposite side of the housing and attaches to a fitting just after the valve to be tested. The tubing passes through the Orsense sensor inside the device housing
Artifical Heart Valve Testing Device The heating coil is shown below. It is located below the tubing between the valve and the sensor and is intended to maintain a homeostatic ambient temperature within the device.
Heating Coil The heating coil is to be made from nichrome With a pre-defined voltage to activate the coil at 7.5 Volts, and a known current of 20mA, this allows for the resistance to be found via Ohm s law, and the resistance is defined by the thickness of the coil. V=I/R Ohm s Law
Device Animation See video file
Device Operation- Programming Necessary equipment and software FlashPIC development board with PIC16F877 microcontroller CCS ICD-S programmer C programming MPLab IDE LM35CZ (temperature sensor) 9V battery
PIC Development Board This board comes equipped with an analog to digital converter which will be utilized in temperature measuring. The board also contains the PIC16F877 microcontroller. An LCD screen is on the board for displaying digital information. A serial binary data connection is supplied in the form of RS-232.
FlashPIC Development Board *Note* this development board image is missing the LCD screen the would be present on the board used for this project. http://www.pages.drexel.edu/~cy56/pic.htm
PIC16F877 microcontroller Most complex unit on the Flash board. Block Diagram Pin Diagram http://www.pages.drexel.edu/~cy56/pic.htm http://www.pages.drexel.edu/~cy56/pic.htm
ICD-S Programmer and Debugger Hardware/Firmware that burns.hex files to microchip PIC. Communicated to the chip through standard phone jack and to PC through RS-232 serial port http://www.pages.drexel.edu/~cy56/pic.htm
Temperature Sensor LM35 Outputs its reading in analog signals Range of ADC on development board is 0 to 5V with 10 bit conversion, so resolution is 1023 Thus formula for analog to digital conversion is Temperature in Celsius = 5.00 * Voltage from LM35 * 100.00/1023.00 http://www.facstaff.bucknell.edu/mastascu/elessonshtml/sensors/lm35ckt.jpg
Temperature Control System Block Diagram Edited from http://www.pages.drexel.edu/~cy56/pic.htm
Temperature control system Schematic with PIC16F877 http://2.bp.blogspot.com/_se0vanai9um/r1qhmxskrxi/aaaaaaaaafk/vgkeryjkp5s/s1600-r/tempearure%2bcontroller.jpg
Multisim Diagram Temperature control system *Note*- When trying to make multisim diagram many parts are missing including the PIC16F877 microcontroller. This is the best representation of image In previous slide
PCB Diagram Temperature control system *Note*- When trying to make multisim diagram many parts are missing including the PIC16F877 microcontroller. Thus the PCB diagram is not as accurate as desired.
Digital Circuit Multisim
Digital Circuit PCB
Flow Rate As mentioned before the flow rate will be measured by the Bio-probe Flow Transducer. When the Bioconsole 560 system is coupled with the Transducer the measurements are accurate to within +/- 5% of the flow rate. The transducers signals are output in digital therefore no ADC conversion is necessary and the signals can be read by the program and microcontroller readily.
Program Code The program code is too lengthy for the powerpoint slides and can be found on the teams website. Within the code is a comparator function which will activate the heating coil if the temperature goes below a certain minimum pre-defined earlier in the code. Once the temperature goes above the goal it is then turned off from the same comparator function
Program Code The flow rate is changed via the pump and therefore the transducers signals are just read from channel 2 and displayed when called upon. This flow rate is different that the pumps flow rate because the tranducer location is at the valve where the flow rate value is desired. Also in the code is the LCD function which calls upon the C program (LCD) to write the desired data to the LCD screen.
Summary Variable flow rate is controlled by Medtronic s blood pump and speed controller and displayed at the location of the pump. The flow rate at the valve is measured with the transducer. Artificial valve can be inserted into sealed door. Clotting factor s are measured using Orsense s NBM-200MP which uses Occlusion Spectroscopy to measure free hemoglobin levels. The NBM-200MP has its own displays to show the measured hemoglobin.
Summary The pump made by Medtronic is for closed loop systems and minimizes the stress of RBC s. The turbulence measuring device is able to measure clotting and work with actual blood with the biocompatible tubing selected. Homeostasis is maintained by monitoring and controlling the temperature, pressure, and flow rate of the closed system.
References http://2.bp.blogspot.com/_se0vanai9um/r1qhmxskrxi/aaaa AAAAAFk/VgKErYJKp5s/s1600- R/tempearure%2Bcontroller.jpg http://www.pages.drexel.edu/~cy56/pic.htm http://www.medtronic.com/cardsurgery/arrested_heart/centrifug al_pump.html http://www.national.com/mpf/lm/lm35.html#datasheet http://www.orsense.com/products