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Re: ECG labs, anyone?

My students do EKGs with the physiology students in our pre-nursing program.
We don't really do physics with the tracings, and it will remain this way
because, to meet the needs of the physiology students, we do this during
the middle of the first semester of physics. My students are basically
involved to ease the anxieties of the physiology students.

We have PASCO computer interfaces and we connect Thornton equipment to
them. (We also do photoplethysmographs and some respiration stuff; we
have equipment for EEGs but I don't think they have ever been done.) The
equipment is easy to set up, but most students can't get it running
independently. Usually they forget to turn everything on, or they don't
plug it in, or they don't have a cable connected correctly. Six weeks
into the semester they aren't very good troubleshooters.

They run resting EKGs, EKGs after exercising, and EKGs after holding their
breath or hyperventilating. They identify P, QRS, and T features and match
them up with contractions and relaxations of the atria and ventricals, and
observe changes with exercise and respiration. The physiology students
think it is great.

We connect through three electrodes and some goopy electrode paste. The
quality of the trace obtained varies widely depending on the quality
of the connection. Some students who can read EKG traces get alarmed
by their traces, as they seem to indicate serious problems; the problem
is in the connections, not their hearts. Typically the heights of the
peaks is quite distorted. The DC level of the trace also tends to
move around as the student breathes or wiggles, but we usually just
redo things until we get a reasonably level trace.

Our equipment isn't terribly robust. Transformers in the amplifier/power
supplies tend to tear loose, and electrode cables are constantly losing
their plugs. Stern warnings about the cables have reduced this problem,
but initially it was common for a lab group to lose one or two during an
experiment, generally by attempting to exercise while connected to the
cables.

At 12:21 PM 12/30/97 -0600, Jim Riley wrote:
Dan,

I purchased the Vernier ekg probe and almost immediately went into the
cardiac business. First I administered one to each of the members of the
department, then showed it to students who wanted one done. It is extremely
easy to do. At this point I have no way of interpreting what we see other
than the usual handwaving reference to the three peaks seen in standard
textbooks. I intend to have some of our biologists give me a better
explanation as soon as I and they can find the time. A physiologist who
teaches part time for us was particularly impressed when he saw a demo of
the device and wants to use it in a class on physiology.

This is where we use it. The students appreciate being able to make their
own EKG. They grumble a lot beforehand (they have to schedule time outside
of class to do it), but they almost uniformly say it was worth it after
the fact.


I did have a couple of interesting results. One was on about the fourth
student who volunteered. I could only pick up a single heart beat and
thought something was wrong until I realized that this was a varsity
swimmer who had a resting pulse of about 28. I was doing a single sweep of
about two seconds. Depending on when I triggered it I might or might not
pick up a heart beat.

We usually collect data for 10-20 seconds and then zoom in on a good
portion of the trace. This makes it easy to determine the heart rate
and it helps when they are trying to listen (with a stethoscope) to
see what sounds the heart makes at what points on the EKG.


The second was on one of our younger chemistry profs. His trace came out
complete garbage both times I tried to record it. I still haven't figured
out what was going on.

My students get garbage quite frequently, but it usually isn't too hard
to pin down the cause. Naturally this is very helpful to you. :)


I too would be interesed in tutorials on the ekg (ecg?)

\At 09:10 PM 12/29/97 -0700, Dan MacIsaac wrote:

(snip)
A second experiment I'm thinking of working up is an ECG experiment. We'd
get the Vernier probeware, and then calculate field intensities based on
the heartbeat plots. Maybe do an examination of the basics of the heartbeat
as well. Can elementary ECG analysis tutorials that include numerical
calculations be found somewheres in the literature?

Dan the ever-demanding

Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
danmac@nau.edu http://www.phy.nau.edu/~danmac/homepage.html


Jim Riley
Department of Physics
Drury College
Springfield Missouri 65802
(417) 873 7233
e-mail: jriley@lib.drury.edu
fax: (417) 873 7432

Carmen Shepard
Maysville Community College