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digital blood pressure measurement

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akey

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hello,

I am making a project on blood pressure measurement project.
actually I have to measure two pressures 1.systolic and 2.diastolic both can be measured as follows...

Usually when the doctor measures the patient's blood pressure, he will pump the air into the cuff and use the stethoscope to listen to the sounds of the blood in the artery of the patient's arm. At the start, the air is pumped to be above the systolic value. At this point, the doctor will hear nothing through the stethoscope. After the pressure is released gradually, at some point, the doctor will begin to hear the sound of the heart beats. At this point, the pressure in the cuff corresponds to the systolic pressure. After the pressure decreases further, the doctor will continue hearing the sound (with different characteristics). And at some point, the sounds will begin to disappear. At this point, the pressure in the cuff corresponds to the diastolic pressure.

My question is how to recognize the start of variation of signal in the controller programming.?
means which will be the best way to know the heartbeats are now starts flowing under the cuff.?

For that I am using MPXV5050 sensor for sensing pressure..
 

BradtheRad

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A small microphone in the cuff will pick up sounds. This signal will need to be amplified.

Then apply the positive portion of the waveform to charge a capacitor.

If a heartbeat occurs before 1.5 seconds goes by, then it maintains charge on the capacitor. This will be the signal indicating 'heartbeat audible'.

When the pressure drops too low for heartbeat to be heard, the capacitor loses charge. That will be the signal 'heartbeat inaudible.'

- - - Updated - - -

Also look at similar threads listed at bottom of this webpage.
 
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bigdogguru

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Latest month's issue of Circuit Cellar Magazine, June 2012, Issue #263, has an article titled, "MCU-Based Automatic Blood Pressure Cuff."

I believe the article discuss the issues and questions you present in your thread.



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akey

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if I shall use microphone in the cuff then will it be affected by the external noise ? and the second thing I want to ask that will microphone able to sense the heart beat.
 

BradtheRad

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A microphone is similar to the stethoscope in the sense that they both pick up sound. You (or the doctor) are distracted by surrounding noise when listening for heartbeats. So you will need to avoid making unnecessary noise until you determine where the threshold of detection is.

It will work best by keeping the sensitive face of the mic close to the skin.

If you amplify the sound sufficiently then it should be able to detect heartbeats. The aim is to filter out the noise and keep the sound of a heartbeat.
 

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bigdogguru

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The Circuit Cellar project I previously referred to uses a single MPX5050 pressure sensor to measure both the blood pressure and the 5mmHg of change from the blood pulsing at a sufficient sampling rate.

MPX5050 Datasheet






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glenjoy

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there commercially available blood pressure measuring kits in the market, you can purchases them in pharmacies, buy one and hack it.
 
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