Re: R-R detection

From: Rich Grise (null_at_example.net)
Date: 07/17/04 

Date: Sat, 17 Jul 2004 10:47:48 GMT

on Friday 16 July 2004 05:42 am, Bob Masta wrote:
> On 16 Jul 2004 01:05:43 -0700, ts5066@ms27.hinet.net (Frankie) wrote:

>>I am seeking a software program that detects heart rate variability in
>>time-series signals. Does anyone know where I could find such software
>>as freeware or shareware? Or some helps to program myself.
>
> If you have a clean-enough recording, you may be able to find
> some threshold level that will reliably detect a QRS complex
> or flow peak. Then you simply note all the distances (in samples
> or msec) between these events and sort them to a histogram
> that shows all the intervals. If the variability is low, they will
> tend to cluster in a central peak at the average interval.

I worked with a box that did exactly what the Frankis seems to be
talking about. The peak detector was written by some other guy, but
it was really simple - just a couple of filters implemented in
software. It gave a very clean, rock-stable one-pulse-per-beat
output, which then got counted.

I don't recall how he wrote the filters, and didn't really
understand it anyway, but basically, take the transfer function
of whatever filter you're building, and code it. Catching a
QRS pulse is almost trivial, if you know what you're doing. :-)
At least Monty Barker (that was the guy's real name, I swear)
made it look easy.

I suppose you'd make something with a response peak at the
fundamental of the (approx) half-sine at the start of the wave,
and even a little analysis of the waveform itself. (this box
even spotted V-Fib - it's just another filter.) 

-- 
Good Luck!
Rich
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