Welch Allyn AED 10 User Manual page 86

User Manual
Study 3
Objective
Comparison of the defibrillation effectiveness of the MRL Orbital Biphasic waveform
defibrillator, with a commercially available Biphasic 2kV defibrillator capable of 360 J in a
simulated higher impedance model.
Methods
A canine model (n=6, 53.7 ± 6.1 lbs) was used in a study that was approved by the
Institutional Animal Care and Use Committee. The animals were anesthetized with 20
mpk sodium pentothal i.v., and maintained as required through an intravenous catheter in
the foreleg. The femoral artery was cannulated and an intra-arterial line was placed for
continuous measurement of arterial blood pressure. The chest was shaved and
defibrillating patch electrodes were placed on the left and right chest walls.
Fibrillation was induced by delivering 60 Hz current to the chest electrodes. The energy
required to defibrillate was determined by a protocol that has been used in several other
biphasic comparison studies. An initial shock strength of 70 to 100 joules was used. If
successful, VF was re-induced after a 5 minute rest period, and the shock strength was
reduced by approximately 20% for the next defibrillation attempt. If the initial shock failed,
a rescue shock was delivered, and after a rest period, VF was again induced. The energy
was now increased about 20% for the next defibrillation attempt. This procedure was
continued until approximately 4 reversals in result were observed with each waveform.
Two ED50 estimation procedures were run in parallel, with the device being used
alternated on each shock. In practice, actual clinical units were used, so the energy steps
were limited to those selectable on the devices tested. The ED50 peak current and
energy was then estimated for each animal by logistic regression analysis.
This study simulated a higher impedance patient by having a 32-
with each subject.
Results
The study consisted of 98 total fibrillation/defibrillation episodes. The mean ED50 and ID
50 estimates for peak current and energy for each animal (to one decimal place) are
shown below. The significance of difference (p-value) was calculated by the Wald test in
each case, and is shown below. Also shown are the mean total durations measured for
each device.
Summary Table -ED50, ID50, & Duration
Mean
ID50 Peak Current (Amps)
Significance of difference (p-value)
ED50 Delivered Energy (Joules)
Significance of difference (p-value)
Total Duration (msec)
Welch Allyn 2kV Biphasic
AED 10 Waveform
5.8 7.4
<0.001
34.3 32.0
0.885
21.3 15.6
Specifications 77
Ω
resistor placed in series