Second Chance Automated External Defibrillator Pads

Defib Task Force (defibtaskforce@gmail.com)

Lisa Jiang, Justin Lin, Joanna Nathan, Carl Nelson, Brad OttoDepartment of Bioengineering, Rice University

MotivationClaiming 300,000 lives annually, sudden cardiac arrest (SCA) is among the leading causes of death in the US. SCA can be caused by cardiac fibrillation, which is treated using Automated External Defibrillators (AEDs). AEDs administer an electric shock that resets the heart, returning it to its regular rhythm. This treatment option is only effective if administered within the first 10 minutes of SCA onset. Effective defibrillation depends on quick and accurate pad placement. Incorrectly placed pads do not deliver the electrical shock through the victim’s heart, and will fail to resuscitate the patient. Substituting the used pads with a new set placed in a different area can fix this problem, but most AED users will not know to do this, and the process itself requires too much time to complete. This increase in time to defibrillate the heart greatly decrease survival in SCA victims.

ObjectiveDefib Task Force aims to create the Second Chance AED Pads to allow untrained AED users to quickly change the shock vector if the initial AED shock fails. The design criteria are displayed below.

Design CriteriaCriterion Test MetricPlacement Accuracy

Ease of Application Test

> 86% of pads placed correctly

Operation Time Ease of Application Test

<10 second increase in average application time

Switch Operation

Ease of Application Test

> 75% of participants flip switch

Durable Under High Voltage

Switch Durability Test

Switch can withstand 200J without malfunction

Secondary Pad Success

Vector Change Analysis

Switch successfully changes vector circuit

Significant Vector Change

Vector Change Analysis

>3 degree change in vector

Cost Effective Cost Analysis < $130 to produce

Second Chance AED Pads

Determining Pad PlacementPurpose Determine optimal electrode separation distance

on the dual pad

Test

Figure C: Pad placement survey.

Seven cardiologists completed surveys to determine optimal placement of the secondary electrode with respect to the first pad.

Results 3 inch displacement between electrode centers

was determined to be the best displacement.

Testing Ease of ApplicationPurpose Compare Second Chance AED pads to

contemporary pads

Test 65 untrained volunteers applied the Second

Chance AED pads onto a mannequin, using pre-recorded voice instructions that simulate a realistic AED operation scenario.

Operation times and placement accuracy were recorded.

Results

Statistical analysis shows that the there is no significant difference between the times to first shock (α = 0.1, p = 0.3).

Testing and Modeling Vector Change

PurposeDetermine if device applies the desired change in vector angleTesting

Used six-electrode system, similar to an ECG Measured voltage along two different vectors

on porcine specimen Matlab model inputs dimensions and distances

between the electrodes and determines the three-dimensional angle change between the cardiac vectors for human and porcine models

Results The porcine trial produced a 4° change in

vector. The Matlab program predicted a 5.8° change

for the human model.

Conclusions Second Chance AED Pads meet or exceed all

design criteria. Total cost: $83 to produce Design significantly improves on control pad

application success rate (100% vs. 60%)

Future Work Test and optimize design

o Animal trialso Clinical trials

Integrate switch design into AED systemso Include switch in verbal commandso Improved instructions

AcknowledgementsDefib Task Force would like to thank Dr. Renata Ramos, Dr. Mehdi Razavi, Dr. Maria Oden, Carlos Amaro, the Rice University OEDK, the Texas Heart Institute, and St. Luke’s Episcopal Hospital.

References Deakin, Charles D. "European Resuscitation Council Guidelines for Resuscitation 2005

Section 3. Electrical Therapies: Automated External Defibrillators, Defibrillation, Cardioversion and Pacing." Resuscitation 67 (2005): S25-37. Print.

Bridy, Marie A., Thomas R. Burklow. “Understanding the newer automated external defibrillator devices: electrophysiology, biphasic waveforms, and technology”. J Emerg Nurs 2002;28:132-7.

Gundry, et al. "Comparison of Naive Sixth-Grade Children With Trained Professionals in the Use of an Automated External Defibrillator." Circulation 100 (1999): 1703-707. Print.

Test Group

Correct Placement

Switch Flipped

Time to 1st Shock

Time from Shocks 2-3

Control 60% N/A 79.2 s 149 s

SC Pads 100% 90% 88.0 s 149 s

Pad Placement

Pad Orientation

Pad Displacement

Switch Withstands high voltage and current Resistant enough to prevent accidental

flips

101

Wiring Plug connector is compatible

with standard AED units.

Figure A: Pad BackThe back of the pad consists of conducting electrode gel and metal plating.

Green wire to electrode B

Blue wire to electrode A

Figure B: Switch DetailsThe switch inside of the project box. The white wire is the main lead from the AED. The blue and green wires lead to the dual electrode pad.

Dual electrode pad Secondary cardiac vector in single pad unit Decreases severity of skin burns Two Electrodes

o 3 inches between centers of electrodes.o Each electrode on pad conducts.

electricity only when manually selected by switch.

Instructional Insert Color-coded:

o Aids placemento Orients pads/switch

Includes body landmarks to aid pad placement

Easy-to-follow