CONTACT: L. E. OHMAN
283 Medical Laboratories
Iowa City IA 52242
(319) 335-6660; fax (319) 335-8034
UI study validates AMA recommendations for defibrillation technique
IOWA CITY, Iowa -- When Dr. Richard Kerber helped update the American
Heart Association (AHA) guidelines for defibrillation in 1992, he believed
then, as he does now, that they specify the best way to achieve success.
Yet, he said the recommendation for apex-to-anterior electrode placement
with gel only on the electrode paddles was intuitive; there was little
actual data to show that successful defibrillation depended upon following
theses specific AHA guidelines on electrode placement.
Kerber, a University of Iowa professor of internal medicine, was disturbed
by the number of defibrillation failures. He suspected, but couldn't be
sure if technique was partially to blame.
"All too often we saw that the electrodes weren't placed properly
or gel was smeared between them--which is understandable when working in
an emergency situation. And with little data, it was unclear how important
it is to follow the AHA recommendations," he said.
Anxious to know if poor electrode and/or gel placement contributed to
defibrillation failure, Kerber and colleagues examined interelectrode impedance
in healthy subjects. In one condition AHA guidelines for electrode and
gel placement were followed, and other conditions were studied in which
electrode placement was too close and/ or gel was smeared on the skin between
They found that following AHA recommendations for electrode placement
allowed the most current to reach the heart, thus providing the best condition
for successful defibrillation. Gel smeared on the skin between the electrodes
and/or too close electrode placement produced an alternate pathway that
shunted current away from the heart, producing a deleterious effect.
Interelectrode impedance was measured using a validated test-pulse method
in five men and five women whose ages ranged from 22 to 48 years.
No high-energy shocks were given to the volunteers.
Impedance was tested in four conditions: 1) electrodes placed in an
apex-to-anterior position with gel only on the paddles (AHA recommendation);
2) same position as in 1 with gel smeared between the electrodes; 3) electrodes
in a parasternal-to-anterior position with gel only on the paddles; 4)
same position as in 3 with gel smeared between the electrodes.
Kerber and his colleagues found that compared to the AHA recommended
technique, the percentage of current transversing the heart was significantly
lower in the other experimental groups-especially when the electrodes were
placed too close with gel smeared on the skin between electrodes.
This study gives strong support to the AHA electrode placement recommendations