topic Re: How to measure distance between R-R peaks in Life Science

How to measure distance between R-R peaks

infra444 — Thu, 16 Oct 2008 14:22:56 GMT

Hi Friends,

I am trying to measure the distance between two R-R peaks and plot the respective frequeny spectrum from that, which is as shown in the attached picture. I could not find how to do it, kindly have a look at my vi.

Thank you,

Regards,

abi

Re: How to measure distance between R-R peaks

rpursley8 — Mon, 20 Oct 2008 15:20:35 GMT

Take a look at the attached. I modified your existing program to read in the data and accumulate the R-R intervals and Heart Rates.

I also allowed the vi to remember the position of the last peak from the previous loop iteration so it can computer the data correctly. Also the program will ask for a file name and end when the EOF is reached.

Re: How to measure distance between R-R peaks

infra444 — Tue, 21 Oct 2008 13:43:13 GMT

Dear Mr.Pursley,

Thank you very much for mod vi, could you please explain me a bit about the changes you made in the mod vi.

Actually I am using a real time data and not from a file, so I tried replacing the input file by a Daq assistant to read the data here in this vi, but it doesnt work. Is it necessary to specify the file dialog to read the file every time. How can I get a real time data using Daq assistant in this vi.

Thank you,

abi

Re: How to measure distance between R-R peaks

rpursley8 — Wed, 22 Oct 2008 14:46:32 GMT

I have commented and modified the previous vi to use DAQ to collect data. Take a look at it and see if it does what you want.

Re: How to measure distance between R-R peaks

infra444 — Thu, 23 Oct 2008 08:49:22 GMT

Dear Mr.Pursley ,

I have a question the vi is still asking for a file name every time I run it, but I dont want to read it frm a file, I want to read it directly from the Daq acqusition device in real time. So for this I just connected the DAQ device to notch filter as shown in the vi, but I think something is missing here. Kindly have a look at it.

Is it necessary to specify a file name every time, because it is just reading the data from the previous file and not the real time measurement when I run the vi.

Thank you for your time.

abi

Re: How to measure distance between R-R peaks

rpursley8 — Thu, 23 Oct 2008 12:58:59 GMT

Sorry about that. I added in the file read to double check the rest of the code and forgot to take it back out. The attached should be right.

Re: How to measure distance between R-R peaks

infra444 — Fri, 24 Oct 2008 08:59:29 GMT

Dear Mr.Pursley

Thank you once again for really helping me out, I will get back to you, if I have any questions in the future.

Re: How to measure distance between R-R peaks

infra444 — Mon, 27 Oct 2008 09:44:59 GMT

Dear Mr.Pursley,

In my program the vi is acquring data for 5 seconds only and then it stops, and all the varying parameters such as heart rate and R-R intervals stop after 5 seconds, and it remains the same, I mean it does not vary or continue further with time.

Say for suppose I need to check the data for 2-3 minutes continously´, the heart rate and the intervals also should change along with time, but thats not happening here, it just reads the data for first 5 seconds and the values remain constant, irrespective of how long you run the vi. I want to make this vi continously running with changing parameters. Kindly advise what I need to do in order to display this.

Thank you,

abi

Re: How to measure distance between R-R peaks

rpursley8 — Mon, 27 Oct 2008 16:55:45 GMT

The program I attached in an earlier message works fine for me. Make sure the Stop button hasn't been pressed before the program has even started.

Re: How to measure distance between R-R peaks

infra444 — Tue, 28 Oct 2008 09:05:37 GMT

Dear Mr.Pursley,

I checked it again with your mod vi it scans for the first 5 seconds and displays heart rates and R-R intervals, and this remains constant from then, only the locations are changing with time and not the respective Intervals and heart rate.

Is this normal, I am little confused here wheather its working correctly or not.

Message Edited by infra444 on 10-28-2008 04:05 AM

Re: How to measure distance between R-R peaks

infra444 — Tue, 28 Oct 2008 09:31:48 GMT

Kindly check the vi with these recorded signals wheather the vi is working properly, these are the recorded signals from my DAQ device.

thank you,

abi

Re: How to measure distance between R-R peaks

rpursley8 — Tue, 28 Oct 2008 14:18:55 GMT

I looked at your files and I do not see much in the way of ECG. The signals are dominated by what I will assume to be a respiration signal. The ECG is there, but of such small amplitude that your filtering cannot be selective enough to separate it from the respiration signal.

If this is the best signal for ECG that you can acquire, then you will have to figure out a new approach.

Re: How to measure distance between R-R peaks

infra444 — Tue, 28 Oct 2008 14:26:18 GMT

thanks you for your reply, ya this is the best signal I could get from Daq acqusition, in fact I have sent you only the better ones, so what method can I use with such a signal, as I am dealing with these signals only and the other conventional ECG I sent before was just used to compare both the ECG's.

ya your right here respiration signals are overlapping with ECG, so is there any way to deal in such a situation.

Re: How to measure distance between R-R peaks

Steve.J — Tue, 28 Oct 2008 15:13:50 GMT

How are you measuring the ECG? Is this signal acquired using regular contact electrodes/gel and a ECG amplifier connected to a DAQ board?

Re: How to measure distance between R-R peaks

infra444 — Tue, 28 Oct 2008 15:21:38 GMT

no this is contactless capacitively coupled ECG, plate electrodes are attached to car seat at the lower back and then the signal is extracted with a ECG amplifier, and a driven circuit which is then fed on to a DAQ acqusition device. This is completely contactless, not attached on to the body using any gel or so.

Re: How to measure distance between R-R peaks

Steve.J — Tue, 28 Oct 2008 15:40:41 GMT

OK - that explains the waveform...

Re: How to measure distance between R-R peaks

rpursley8 — Tue, 28 Oct 2008 16:28:25 GMT

You should look into LMS adaptive filtering. This should be able to filter out the respiration signal.

Re: How to measure distance between R-R peaks

rpursley8 — Tue, 28 Oct 2008 16:55:44 GMT

Take a look at the attached. I have added a simple adaptive filter that effectively filters out the respiration. The ECG signal is still pretty poor, but easier to see.

Re: How to measure distance between R-R peaks

infra444 — Wed, 29 Oct 2008 09:11:39 GMT

thank you for mod vi, I am not very well conversed with adaptive filter toolkit, can you expalin a bit about it and also is it not possible to measure the heart rate and R-R intervals with this adaptive filter concept.

回复： How to measure distance between R-R peaks

ZJ.Gu — Thu, 30 Oct 2008 07:32:23 GMT

Hi,

I have a try of you signal of "R10-R10_closed cover_Bhavin1_1.lvm". ECG signal is very weak. However, choosing a suitable filter will help improve the SNR. Then using peak detection technique to find the heartbeats.

During the peak detection ,the threshold should be adaptive as the ECG signals are so weak and changing. Here I only set to a fixed threshold 0.02. For adaptive threshold in ECG QRS detection, you could refer to the paper (although it is very old :))

J. Pan and W.J. Tompkins, “A real-time QRS detection algorithm,” IEEE Trans. Biomed. Eng., vol. 32, pp. 230-236, 1985.