Our main objective in this project is to create an automatic blood pressure device using a finger pulse sensor combined with a DSP processor.
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High blood pressure is the cause of hundreds of thousands of deaths every year and many people are not aware they have high blood pressure.
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High blood pressure cause extra stress to be placed on the inner walls of arteries causing numerous health issues class3_slides.pdf, slide 2
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Non-invasive automatic blood pressure devices can be used by everyday people in their own home.
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Automatic blood pressure devices would allow for
Americans to monitor their blood pressure on a daily basis. source: http://upload.wikimedia.org/wikipedia/ commons/thumb/e/e5/Diagram_of_the_human_heart
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Blood pressure is broken down into two parts:
Systolic: higher number, measured when the ventricle tenses and forces blood out
Diastolic: lower number, measured when the ventricle relaxes and fills with blood
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Blood pressure is measured through the brachial artery in the arm, right above the elbow.
Class1a_vu.pdf, slide 9
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Recommended blood pressure level 120 mm Hg for systolic over 80 mm Hg for diastolic.
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Systolic blood pressure levels between 139-121 mm Hg and diastolic levels between 89-
81 mm Hg is considered pre-hypertension
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Systolic blood pressure levels greater than 139 mm Hg and diastolic levels greater than 89 mm Hg is considered hypertension
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Preformed blood pressure tests on fellow students to get a better understanding of how blood pressure measurements are taken manually.
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Then we analyzed pre-recorded sound files in the computer program Matlab to practice analyzing signals.
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Generated a graph of the pressure signal and a graph of the stethoscope signal over the duration of the test.
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Demodulated the signals by running them through a Matlab program and generated two new graphs.
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Analysis of graphs gave us a better feeling on how to analyze signals and determine blood pressure measurements from those signals
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Developed a circuit using a breadboard which conditioned the signal for processing.
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Prior to processing and analyzing a signal the signal must first be conditioned in order for the DSP chip to be able to process it.
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Signals received by the finger pulse sensor are small so they must first be amplified
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Signals are also received in analog format where as the DSP chip processes digital signals.
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As well as being amplified the circuit also converts the signal to digital so it can be processed.
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After building the circuit to process the signals we began processing pre-recorded signals using the program CCStudio.
Pressure signal
Finger pulse signal
Time (seconds)
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We then began trials with the finger pulse sensor, attempting to obtain our own signals.
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Upon obtaining a good signal se recorded the signal and processed it using the program
CCStudio in the same manner as the pre-recorded signals.
Pressure signal
Finger pulse signal
Time (seconds)
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After processing our finger pulse signals we then plotted the pressure signal and finger pulse signals in order to get a better understanding of when to record systolic and diastolic pressures.
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After perfecting our signal we ran a final analysis of our signals using a C program provided for us and we obtained our blood pressure measurements.
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We were able to successfully obtain automatic blood pressure measurements using the finger pulse sensor and the DSP chip.
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Our final systolic blood pressure level was measured as 105 mm Hg and our final diastolic level was measured as 75 mm Hg.
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We found the finger pulse sensor to be difficult to use and inaccurate. In many cases we were required to perform multiple tests in order to receive fairly accurate results.
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The finger pulse sensor was very sensitive so it tended to pick up outside noise which interfered with our signal causing inaccuracies in our results.
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The DSP chip was able to process the signals without a problems.
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If we were to further develop an automatic blood pressure device using a finger pulse sensor and a DSP chip we would need to reduce the size of the circuit and DSP chip by removing all excess pieces and compacting everything onto one board.
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By reducing everything to one board we can cheaply mass produce the board
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The final step would be to embed all the components into one self-contained system for sale to consumers.