Blood pressure. Outline for today’s class. Question on Blood Pressure – review constants Cuff-with variety of methods to detect blood flow Errors in measurements- Bernoulli Tonography Solid state sensors Other pressure sensors 2 nd order model of catheter Statham / Millar transducers.
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Outline for today’s class • Question on Blood Pressure – review constants • Cuff-with variety of methods to detect blood flow • Errors in measurements- Bernoulli • Tonography • Solid state sensors • Other pressure sensors • 2nd order model of catheter • Statham / Millar transducers
Blood Pressure Basics • Definition Pressure = Force/Area • At 0 deg C and standard gravity 981 cm/sec2 • Corrected for atmospheric changes • Units 1 torr =1 mm Hg =1328 dynes/cm2 =13.6 mm H20 =13.1 mm saline =12.9 mm blood
Blood pressure questions • Where is the highest blood pressure in the body? • Where is the lowest blood pressure? • What is the minimum pressure needed to survive? • Why is your heart located in the chest? • How does a giraffe pump blood to it’s head? • What is your blood pressure in Denver compared to sea level? • Where are the pressure sensors in your body?
Blood Pressure questions cont • How is blood pressure regulated? • What is the relationship between heart rate and body size? • What is the relationship between heart rate and respiration? • How do you measure blood pressure in the capillaries? • What is your blood pressure in Denver compared to sea level? • Does blood pressure have to be pulsitile? • Does the pulse reach all the body at once? • What is origin of Korotkoff sounds?
Sources of Error-velocity effect Total Energy= Pressure energy + velocity energy + height energy E = Ps + Mgh +(1/2)mv2 Where: Ps = Static Pressure M= mass g=gravitational accelleration V=velocity
Bernoulli effect In this example of a fluid flowing initially in a large cylinder and then flowing in a small cylinder before returning to the large cylinder, note that the velocity in the middle must increase. Since the Total Energy must be the same, the increased velocity means more kinetic energy, the resulting static pressure must be less
Other 2nd order systems Mechanical systems Body motion Fluid systems Transducer sensors Oxygen diffusion models Feedback model elements
Statham Transducer Dangers of Air Bubble -loss of frequency fidelity -air bubble entering blood -Possible stokes or ministrokes
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