Ttelmah
Joined: 11 Mar 2010 Posts: 19513
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Posted: Sat May 14, 2011 8:33 am |
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The standard measuring system is the same in all normal cases.
You measure the presence of the pulse. and increase the pressure in a cuff. By detecting the 'pump', and 'return' parts of the pulse, and when each is affected, you have a direct measure or the two components required.
You have to remember that the value depends on where the sensor is in height, relative to the heart.
It is possible to detect the pressure now, without a cuff, but not with a 'fingertip' device. The normal ones of these detect the pulse only, not the actual pressure involved (normally infrared sensors).
Without a cuff, you have to measure the actual blood flow velocity. The nearest to a fingertip device, was one developed at MIT a couple of years ago:-
<http://www.ideaconnection.com/new-inventions/measuring-blood-pressure-without-a-cuff-02342.html>
There are a few others in use, some quite specialised (head sensors!), but most require calibration using a cuff, for the patient involved, since the actual pressure depends on the elasticity of the blood vessel, it's diameter, and the flow velocity.
So not really suitable for basic testing.
Basic pulse sensors, are cheap now.
Best Wishes |
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