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Blood Pressure Sensor

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Elif Elibol

on 6 May 2013

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Transcript of Blood Pressure Sensor

BIOMEDICAL INSTRUMENTATION PROJECT – ELİF ELİBOL BLOOD PRESSURE SENSOR Blood pressure without further specification usually refers to the systemic arterial pressure measured at a person's upper arm and is a measure of the pressure in the bronchial artery, the major artery in the upper arm. A person’s blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure and is measured in millimeters of mercury (mmHg), for example 120/80. High blood pressure is a common risk factor for heart attacks, strokes and aneurysms, so diagnosing and monitoring it are critically important. However, getting reliable blood pressure readings is not always easy.
Visits to the doctor's office can provoke anxiety that distorts blood pressure readings, and even when accurate, such visits provide only one-time snapshots of the patient's condition. To overcome these obstacles, engineers have built a wearable blood pressure sensor that can provide continuous, 24-hour monitoring. BACKGROUND Blood pressure can change from minute to minute, so continuous monitoring offers a much broader picture of cardiovascular health. The new monitor, which loops around the wrist and the index finger, is just as accurate as traditional cuff devices but much less cumbersome, allowing it to be worn for hours or days at a time. Mercury Manometer Auscultatory method Conventional blood pressure monitoring systems (non-invasive sensors) Traditional blood pressure monitoring requires a cuff, wrapped around the upper arm and inflated until blood flow is completely cut off. The examiner then gradually releases the pressure, listening to the flow until the pulse can be detected.
With the new monitor, no cuff is required. Instead, the device takes advantage of a method called pulse wave velocity, which allows blood pressure to be calculated by measuring the pulse at two points along an artery. With the new sensor, no cuff is required.
Device takes advantage of the method called pulse wave velocity which allows blood pressure to be calculated by measuring the pulse at 2 points along an artery.
This was developed at MIT's d'Arbeloff Laboratory for Information Systems and Technology. Current blood pressure sensors in use In early models, the researchers used the heart as one of the points, with a heart monitor measuring the EKG. However, EKGs aren't always accurate, and a heart monitor can be uncomfortable, so the researchers decided to use two points on the hand instead.
That posed a challenge because blood pressure in the hand varies depending on its position: If the arm is raised above the heart, the pressure will be higher than if it is below the heart. The researchers solved that dilemma by incorporating a sensor that measures acceleration in three dimensions, allowing the hand position to be calculated at any time. This not only compensates for the error due to height changes, but also allows them to calibrate the sensor for more accurate calculation of blood pressure. As the wearer raises the hand up and down, the hydrostatic pressure changes at the sensor. Correlating the change of pulse wave velocity to the hydrostatic pressure change, the system can automatically calibrate its measurement.
Once the blood pressure information is gathered, the data can be transmitted via radio signals or wireless Internet. The device runs on a tiny battery, about the same size as the ones that power watches. LONG-TERM IMPLANTABLE BLOOD PRESSURE MONITORING SYSTEM The system employs an instrumented elastic cuff, wound around a blood vessel.
Operates in a linear “diameter versus pressure” region of the vessel for real time blood pressure monitoring.
The elastic cuff is made of soft bio-compatible rubber, filled with bio-compatible insulating fluid with an immersed MEMS pressure sensor.
The MEMS sensor detects the vessel blood pressure wave form with a constant scaling factor, independent of the cuff bias pressure exerting on the vessel. Implantable blood pressure monitoring system Advantages This technique avoids vessel insertion.
Also substantially minimizes vessel movement restriction due to the soft cuff elasticity.
Attractive for minimizing long-term adverse biological effects. WIRELESS BATTERY-LESS IN VIVO BLOOD PRESSURE SENSING MICRO SYSTEM Wireless powering and data telemetry are also incorporated in the micro system.
This eliminates the need of external wire connections and any bulky battery.
The micro system can be used to obtain reliable measurements without suffering from stress induced distortion. Wireless Battery-less In Vivo Blood Pressure
Sensing Micro system Microsystem architecture A piezoelectric blood-pressure transducer has been developed for indirect blood-pressure measurements on a wrist for the clinical environment.
Use of a piezoelectric ceramic beam with a relatively high impedance amplifier provides a position-insensitive pressure measurement, which is very much desirable for a long-term measurement. PIEZOELECTRIC BLOOD PRESSURE SENSOR High mechano-electrical sensitivity
Low impedance output
Wide operation temperature
Molded air pressure hose bonded with shielding cable Advantages A piezoelectric blood-pressure transducer It consists of two parts: a pressure-sensing membrane and a fiber-optic displacement transducer which is based on the light intensity loss caused by angular misalignment between two fibers.
The light intensity change is registered by a photo diode.
The pressure transducer has been evaluated for static and dynamic pressure measurements. Not only does it have adequate linearity and frequency response, safety, and small size, but also it may be an attractive device for developing multiple-site pressure-detecting catheters. FIBER-OPTIC SENSOR FOR BLOOD PRESSURE MEASUREMENT Fiber-optic transducer for blood pressure measurement Consistent and accurate readings during blood pressure monitoring.
Components that simplify setup.
The transducer can easily be mounted on either the patient, bed or IV pole.
Fully integrated flow-thru component design simplifies filling and de-bubbling.
Superior fluid path visualization.
3cc or 30cc per hour flow rates. DISPOSABLE ARTERIAL BLOOD PRESSURE SENSOR Disposable arterial blood pressure sensor MEMS sensor Insulating Liquid Vein Cuff THANK YOU FOR LISTENING Blood pressure (BP), is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation.
During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure. The blood pressure in the circulation is principally due to the pumping action of the heart. Differences in mean blood pressure are responsible for blood flow from one location to another in the circulation. The rate of mean blood flow depends on the resistance to flow presented by the blood vessels. Mean blood pressure decreases as the circulating blood moves away from the heart through arteries and capillaries due to viscous losses of energy. Mean blood pressure drops over the whole circulation, although most of the fall occurs along the small arteries and arterioles. DESCRIPTIONS
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