USB-6210 ECG setup

[McMurray]

Hey everyone,

I just got a new USB-6210 in the lab, and I'm trying to set it up to record EKGs.  I don't have an EKG machine or anything, I'm hoping to be able to do it all with the DAQ.  Does anyone have any experience with this?  Will a simple differential voltage measurement suffice?  Do I need a ground?  How do I need to set up my EKG electrodes on my subject?  I've never tried to do EKG work before, so as you can see I'm completely lost here.  Thanks for any help you can provide.

Matt

[Steve.J]

Don't try to record ECG signals directly with a DAQ board - it won't work and it's not safe.

Please read my posting on our Biomedical User Group here:  http://decibel.ni.com/content/docs/DOC-4670

[dickdrago]

If you are talking about sensing a pulse through the skin using an daq a/d isn't dangerous but you will need a pre amp with some kind of 50/60 hz noise filter at the least.

[Steve.J]

Dickdrago - it is dangerous to connect a person directly to a DAQ board using low-impedance electrodes/gel.  There is no protection from fault currents originating from the DAQ board and/or computer that may occur for a variety of reasons and no protection to the subject if they inadvertently come into contact with line voltage (the DAQ board and computer will complete the circuit and they will be electrocuted).  Since a preamplifier is needed anyway to provide a true, balanced differential input with a high CMRR with gain and bandpass filtering, this same amplifier can provide the protection needed to ensure the safety of the subject.

[McMurray]

I'm just trying to get a HR measurement (like a cardiac tachometer).  I can see the HR on my ocilloscope and volt meter, so should I be able to do something similar in Labview with my DAQ, right?  I don't see how using a DAQ as a voltmeter is inherently dangerous.  I'm doing it in rats anyways...  Can't I program an amplifier and filter in LabView?  Any more advice?

[Steve.J]

OK - let's talk more about what exactly you are doing and what equipment you are using.  You say that you are using rats and that you can "see the HR" on your o-scope and volt meter.  What are you using to connect to the rats (what kind of sensors or electrodes) and where are they connected?  Are the rats awake and mobile, or anesthetized?  Do you see the HR (heartrate) or the actual ECG waveform on your scope?  What do you mean you can see HR on your voltmeter - is this a voltage representation of the heartrate from a pulse sensor?  I'm confused.

Using a DAQ board and PC is not inherently dangerous - it's just not safe and we cannot recommend it.  It's like going boating without a life vest - boating is not inherently dangerous, but $%& happens and when your subject matters to you, then you should take precautions.  Like I said, since you almost always need some kind of amplifier to get a decent, reliable biosignal from an animal/person, you may as well use one that is designed to provide some protection anyway.  If it is a rat or frog or lobster, you may not care if it keels over because there was a power surge in your lab - that's your call.

Back to your questions - tell me more about your equipment and setup and I'll see if I can help you.

[McMurray]

When I hook myself up to the ocilloscope, I see a peak everytime my heart beats.  That's all I need.  Just the peak.  I have Labview 8.6.1, the USB-6129, a bunch of wire, and a bunch of ECG sticky pads.  I don't have an amplifier or an actual ECG machine.  I just need to count the voltage peaks and the time between them.  Thanks for all the help.

Matt

[Steve.J]

How are you hooking yourself up to the oscilloscope?  Are you using the ECG electrodes, and if so, where are you putting them?  What kind of scope are you using and does it have a differential input?  How big is the peak?

You can always try to connect the oscillocope or USB-6210 directly to your rats and see if you can also see a peak for every heartbeat, but I don't think you will have much luck. The key to getting a reliable heartrate measurement is to get a clean ECG signal - its hard enough to get a reliable rate even with a clean signal...it will be almost impossible with a noisy one.

If you just need heartrate (and not the ECG waveform) you may find it easier to measure pulse.  I believe that there are sensors that can detect pulse that attach to the tail of the rat that probably can interface directly with the USB-6210.

[McMurray]

I have 2 BNC cables that connect to the oscilloscope, with alligator clips on the ends.  These are attached to ECG sticky pads. I'm sticking one pad on my sternum and one on my side.  The scope does have a differential setting, which I'm using.  I have no budget for this project, so new equipment is not an option.  With the rats I'll be using two safety pins that I have soldered to my cables, which then go into the USB-6210.  The safety pins go through the skin on each side of the rat and are glued into place with surgical superglue (the rat is anesthetized during the surgical procedure).

[McMurray]

If you can do it with a sound card, I hope to god you can do it with the 6210...

http://www.eng.utah.edu/~jnguyen/ecg/ecg_index.html