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Ken
While I don't use Biopac, I do an ECG lab with a my
students............we borrow a ECG machine from the EMT folks, run a minute
long strip on everyone, and have a careful look at the strips. We then
identify normal sinus rhythm in all the appropriate strips, and look for reasons
why someone may be out of normal sinus rhythm, and still be normal........., ie,
sinus bradycardia, sinus arrhythmias, etc,...........It's a great exercise in
the variation that occurs in individuals, and an excellent lead in to pathologic
arrhythmias that nursing/EMT students learn with subsequent
classes...........
Anyway, where am I going with this? We often see
variations in heart rate with respirations. After several years of doing
this, I've found that the best effect can be seen in those with a low resting
heart rate. If you have any athletes in your group, with a heart rate in
the low - mid 50's, you'll see marked variations in rate with
respirations. You might want to pay particular attention to the results of
these individuals......they can often provide some great teaching
materials.........
----- Original Message -----
Sent: Saturday, January 25, 2003 7:46
PM
Subject: Respiration and [HAPP-L]
Electrocardiograms [HAPP-L]
Dear HAPSters,
Can anyone help me out here?
I am
about to run the Biopac electrocardiography exercises for the first time, and
I am wondering about the physiological relationship between breathing and the
ECG. In the "ECG I" chapter, there is an experiment in which the students are
to observe and measure changes in the ECG during deep inspiration and
expiration. However, in the data analysis section and lab report questions,
there are no further references to this, much less any physiological
explanation of why the ECG should change during deep breathing -- the
whole phenomenon just seems to disappear from further consideration in the lab
manual and in the students' writeup. Nor do I find any discussion of the
effects of respiration on the ECG in Guyton & Hall, Berne & Levy,
Harrison's, or Cheitlin's Cardiology, nor was the vertebrate
comparative physiologist in my college department able to help. (There's only
one to consult; we're not a large department.)
I offered him the
conjecture that the thoracic pressure changes during respiration may affect
the arterial baroreceptors and thus activate transient baroreflexes, to be
reflected in changes in heart rate. He at least thought that was a reasonable
hypothesis. But the screen capture in the Biopac lab manual shows (but does
not discuss) what appear to be changes in voltage rather than heart rate. My
feeble intellect can't imagine why the respiratory rhythm would cause voltage
changes in the ECG, or what that would mean physiologically.
I am
running this in my two lab sections at 1:00 (EST) Mon & Wed this coming
week. I'd be very appreciative of whatever explanations anyone can offer
before then, but even afterward, it would be useful to have more insight into
this for the benefit of my future classes. I hate just exhorting students to
measure something and compare numbers with no insight into what the numbers
and comparisons mean.
Many thanks for any help you can
offer.
Ken
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