(no subject)
Ed Thompson (thompson@VAX2.WINONA.MSUS.EDU)
Fri, 16 Apr 1999 11:13:55 -0600
Jay Thal recent wrote about differences between written BSA, AHA, ARC, etc.
protocols and what Dr. Heimlich stated on TV:
Way back mumbly-mumble years ago, I served as a CPR instructor for both
American Red Cross and American Heart, including stints on regional course
development committees. This issue was around even then: Dr. Heimlich has
often disagreed with how "his" maneuver is taught. As a professional
physiologist, I'm afraid I have to side with the written materials on this one.
Dr. Heimlichs procedure for clearing laryngeal and pharyngeal obstructions
was indeed revolutionary and has saved countless lives - in essence the old
way was to hope and pray. However, what he developed was just that: a new
procedure. In the years since, literally thousands of researchers have
examined the details of this procedure and refined it based on what really
does and not work "in the field". These refinements are what are taught,
not the original procedure.
For example, you noted that he claimed "3-4 thrusts should be employed to
expel water from the lungs prior to starting CPR". Unfortunately, you would
have ten seconds or so, because any water which gets into the alveoli will
be very rapidly absorbed into the blood (for those of you with physiology
courses, look up "colloid pressure"). Besides which: most drowning deaths
occur from spasm of the larynx, with significant amounts of water entering
the lungs only after this has relaxed (the person is close to dead). On the
other hand, there is a lot of research evidence that shows doing the
Heimlich maneuver after drowning CAN indeed reflexively stimulate
respiratory movements and thus pull air into the lungs.
As for asthma: this is not primarily an obstruction which can be cleared -
it is a narrowing of the tubes (bronchi and bronchioles) which carry air in
and out of the lung. It can be caused by a variety of factors including
allergies, infections, exposure to irritants or drugs, or it may just appear
with no identifiable cause. In any case, the treatment is to get the
airways to get wider. In chronic asthma, plugs of mucus do indeed form in
the airways, but these are particularly thick and sticky. The evidence is
strong that sharp increases in thoracic pressure (the Heimlich maneuver)
have little if any effect on dislodging these.
But: there is good evidence that regular and repeated increases in thoracic
pressure, in effect regularly massaging the lungs (in contrast to a few
sharp increases in pressure) DOES have a beneficial effect in loosening
mucus and clearing it out of the airways. Perhaps this is where he was
coming from.
Ed W. Thompson Ph.D.
Associate Professor of Biology
Director of Cytotechnology
Winona State University
Phone: 507-457-5271
FAX: 507-457-5681
thompson@vax2.winona.msus.edu
http://bio.winona.msus.edu/thompson
