anup pillai dhanya premkumar nair. current blood pressure sensors in use background long-term...

Anup PillaiDhanya Premkumar Nair

Current blood pressure sensors in use Background Long-Term Implantable Blood Pressure

Monitoring System and Advantages Wireless Battery less In VIVO Blood

PressureSensing Micro system and Advantages

System Architecture Our Objectives Timeline and Division of work Conclusions

To diagnose critical medical conditions like hypertension

-causes strokes, heart attacks, heart failures

Low blood pressure causes hypotension, which results in dizziness, fainting or shock

Auscultatory method Mercury Manometer

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

In vivo-Latin for “within the living”

Experimentations are done using a whole, living organism

In vivo monitoring is critical for developing effective treatments

Long-Term Implantable Blood Pressure Monitoring System

Wireless Battery less In VIVO Blood PressureSensing Micro system

The system employs an instrumented elastic cuff, wound around a blood vessel

Operates in a linear “diameter v.s. 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.

Cuff

Vein

Insulating Liquid

MEMS sensor

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 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

The sensor specified in the background exhibits increased noise levels

The transmitter of the same dissipated a 80% of the system power

Our objectives are: a) To design a similar sensor which exhibits

less noise levels

b) To design a better and more power efficient transmitter for the sensor

To find a solution which exhibits less noise levels

We began by investigating the reason for the high noise levels in the current design

Animal body vapor penetration into the device

Affect the functioning of the electrical connections within the sensor.

The high impedance node can be highly sensitive to vapor penetration

Electrical connections between the sensor diaphragm and IC chip

Protection for moisture penetration is required for the sensor diaphragm as well as the electrical connections between the sensor diaphragm and IC chip.

A passivation layer, such as silicon dioxide (SiO2) and silicon nitride (Si3N4), can be deposited on the top of diaphragm.

An encapsulant material with strong moisture resistance can be used to protect the bond wires between the sensor and IC before applying silicone passivation layer.

To design a better and more power efficient transmitter for the sensor

In the microsystem, an oscillator based FSK transmitter was employed for data telemetry

This transmitter was on throughout and hence resulted in 80% power dissipation

To use a transmitter operating with a low duty cycle

One can also use a transmitter with an increased bandwidth

If the sampling frequency is 2 kHz, with data rate of 48 kbps, corresponding bit rate is 24 per 0.5 ms

This is the current specification for the system

Instead if we the transmitter is designed to be on for 0.05 ms and off for the remaining 0.45 ms

This results in one order magnitude power reduction at increased data rate of 480 kbps

This corresponds to 72% overall system power reduction

February March April May

Research project topic and preparation for report 1

Report 1

Objective 1

Presentation 2

Objective 2

Final Report

First Objective:

To design a similar sensor which exhibits less noise levels-A. Pillai

Second Objective: To design a better and more power efficient

transmitter for the sensor-D. Nair

A review of current in-vivo blood pressure sensors was presented in this review study

We identified the potential problems with existing solutions

We have proposed two solutions that will enhance the performance of the current design

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