Microsoft Excel question, please help

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  • #1
Ush
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Main Question or Discussion Point

I have various EKG graphs. I need all of the maximum and minimum voltages for each period. The periods are not all the same length. The maximums and minimums all vary.
Is there any way I can do this?
Note: it'll be hard selecting chunks of data and then finding it from that because there's nearly 2500+ values for voltage per a 12 second reading.

An example of a EKG graph is below.
[PLAIN]http://img210.imageshack.us/img210/184/examplefw.jpg [Broken]

thank you
 
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Answers and Replies

  • #2
1,758
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From your data I'm not sure what you mean by maxima, minima and period. Are the peaks inside the noise also considered maxima? If not, how far above the noise must a peak rise before it is considered a peak?

In problems of this sort it is important to carefully define your objective. As you refine your definition, many times the solution becomes obvious.
 
  • #3
Ush
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I was referring to the QRS wave (the large, sharp peaks)
please see attachment below.
 

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  • #4
Ush
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also;
some of the noise is at the same level at the maximums for some of the EKG's
see below

[PLAIN]http://img268.imageshack.us/img268/5008/examplevn.jpg [Broken]
=/
 
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  • #5
1,758
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Good analysis.

Can you think of a way of distinguishing between the peaks you want and the ones you don't. Obviously voltage won't work. What about the amount it rises above the noise? The peak itself might be distinguished by a reversal of slope.

Is the minimum the the first reversal of slope from negative to positive after a maximum?
 
  • #6
Ush
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The minimum is the first reversal of slope after the maximum
I'm not sure about another way to define maximums.


btw, thank you so much for helping me, I appreciate it =)
 
  • #7
Ush
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looking at the graph again. It's apparent that the voltage rises at least 0.5mv without reversal of slope. The noise goes up and down many many times, none of it reaches 0.5mv without reversal of slope.
Can this be used to help define maximum?
 
  • #8
Ush
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--Issue is solved.
 
  • #9
berkeman
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--Issue is solved.
Glad to hear that. BTW, what was causing all of the low-frequency artifacts? Was the patient moving a lot? Which lead is this from, Lead-II?
 
  • #10
Ush
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Lead-I
the subject was as still as possible- the noise is most likely from breathing, The relationship between exercise and voltage were being tested so it's not too surprising. EKG's usually do have a fair bit of noise-
This is part of a physics course.. Each lab we're given different equipment and instructions on how to use the equipment. We have to look at how the equipment works and then make up some sort of hypothesis we can test and then perform the experiment and write a formal report on our findings. For this particular lab we were given an EKG apparatus, voltmeter, conductive paper and power supply-
 

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