Second Chance Automated External Defibrillator Pads Defib Task Force Lisa Jiang, Justin Lin, Joanna Nathan, Carl Nelson, Brad Otto Department of Bioengineering, Rice University Motivation Claiming 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. Objective Defib 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 Criteria CriterionTestMetric Placement 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 EffectiveCost Analysis< $130 to produce Second Chance AED Pads Determining Pad Placement Purpose  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 Application Purpose  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 Purpose  Determine if device applies the desired change in vector angle Testing  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 trials o Clinical trials  Integrate switch design into AED systems o Include switch in verbal commands o Improved instructions Acknowledgements Defib 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): S Print.  Bridy, Marie A., Thomas R. Burklow. “Understanding the newer automated external defibrillator devices: electrophysiology, biphasic waveforms, and technology”. J Emerg Nurs 2002;28:  Gundry, et al. "Comparison of Naive Sixth-Grade Children With Trained Professionals in the Use of an Automated External Defibrillator." Circulation 100 (1999): Print. Test Group Correct Placement Switch Flipped Time to 1 st Shock Time from Shocks 2-3 Control 60%N/A79.2 s149 s SC Pads 100%90%88.0 s149 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 Back The 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 Details The 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 placement o Orients pads/switch  Includes body landmarks to aid pad placement  Easy-to-follow