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R-R detection

Discussion in 'Electronic Basics' started by Frankie, Jul 16, 2004.

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  1. Frankie

    Frankie Guest

    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.
  2. Bob Masta

    Bob Masta Guest

    This sounds like *way* too specialized to be something offered as
    freeware or shareware, or even as a consumer product. There may
    be software that a research lab could provide, but you'd have to
    figure out which lab to contact. Perhaps a literature search to see
    who is doing research in this area?

    Assuming you already have the time-series recorded as a file,
    you can try having a go at this yourself. However, your results
    will depend entirely on how good a signal you have. Your EKG
    signal must be really clean and stable to pick off peaks reliably.
    That means the subject doesn't move around during recording.
    Or, if you are only looking for gross interval variability, you might
    get better results with an optical flow sensor. (Haven't used
    those 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.

    However, a simple threshold may not work well, and you will
    need to have something fancier. One method is to have a
    series of "hoops" the signal must "jump through": It must
    be below a certain level to indicate the inter-event time,
    then it must rise at a certain rate to indicate the start of
    the event, etc, etc. These are typically tweaked by hand
    for best reults. Yu can also try a simpler approach by
    having the threshold self-adjust to some percentage of
    the last peak seen.

    Good luck!

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  3. Rich Grise

    Rich Grise Guest

    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.)
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