Pneumatic Chest Compression Device for CPR Kyra Ceceris

Pneumatic Chest Compression Device for CPR Kyra Ceceris, Dan Metzinger, Tina Mornak Abstract More than 300, 000 Americans die of cardiac arrest each year, and more than 95% of cardiac arrest victims die before reaching the hospital. 1 In a study published by the AHA, in-hospital chest compression rates were found to be below resuscitation recommendations. 1 With recent changes in the American Heart Association (AHA) CPR guidelines stressing the importance of chest compressions, there is a need for a device that can assist administrators of CPR. This device must provide consistent chest compressions while reducing end user fatigue. One proposed solution is a air powered foot pump and inflatable chest cuff. The device is highly portable and lightweight allowing for chest compressions that are consistent and less tiring then conventional CPR. Introduction More than 11. 4 million people a year are taught CPR; almost half are paramedics or other health workers. 1 Effective CPR can double chance of survival. 1 However, CPR is performed for extended periods of time leading to fatigue and compressions that are less effective. 2 Recent studies have shown that performing chest compressions without giving rescue breaths may increase survival after cardiac arrest. The studies recommend new guidelines stressing continuous compressions for 4 minutes, followed by a rate of 100: 2 compression-ventilation ratio. 3 Since current AHA guidelines recommend a 30: 2 compression-ventilation ratio 4, this challenges CPR administrators to effectively provide reliable compressions for longer periods of time. Currently, several designs of CPR devices are being marketed and tested. However, these devices are bulky, heavy, and often expensive, making them unpopular. Some of these devices provide circumferential compressions, which have been shown to have the potential to generate better hemodynamic characteristics than conventional CPR. 5 Challenges in creating this type of device must be addressed and such a device could be used as frequently as Automated External Defibrillators (AEDs). The project objective was to design and create a pneumatic chest compression device for CPR that is small, portable, light-weight, and inexpensive. This device will also provide circumferential chest compressions. This device must be able to provide reliable compressions over long periods of time, while reducing the fatigue in the provider of conventional CPR. Methods Device Design: In order to obtain the goal of a lightweight device that provides circumferential compression, initial designs were devised to have a foot powered air pump, inflatable chest cuff, and tubing to connect both components. The entire system was to be a closed loop system having a constant volume of approximately 2 liters of air. The cuff was designed to be easy to apply to the patient with Velcro as well as completely collapsible Prototype Fabrication: Stock parts were sourced and modified to conform to specifications and goals. Air powered foot pumps were converted to inflate closed loops systems by sealing one hole with cut acrylic, rubber gaskets, and machine screws. Nylon thigh cuffs with Velcro were fitted together to create a cuff capable of fitting around an average male torso. 3 ply polyethylene bladders were then inserted into the Nylon cuff as an inflatable component. Systematic tubing with I. D. of ¼’’ or larger was used to connect components. Testing Methods: The device went through initial strength testing to ensure cyclic compression of the pump would not fail nor rupture the bladders. Also, cyclic frequency time tests of the device were performed to determine full inflation/deflation frequencies. Lastly, the volume of air displaced by the foot pump was experimentally determined by water displacement in a container. Results By an average of manufacturer specifications, experimental design, and volume calculations, the modified foot powered air pump component displaces 1. 9 liters of air. The cyclic frequency time trials of the device tested on a manikin are shown in Table 1. The final prototype design with modified foot pump, chest cuff, and systematic tubing is shown in Figure 1 and Figure 2 Figure 1 Figure 2 Discussion At this stage in development the device has a respectable cyclic frequency average of approximately one full compression and near full deflation per minute. Although the device falls slightly short of current suggested CPR frequencies, the device shows promise in the following areas. First, the small size and weight of the device surpass current devices on the market and those being tested. Second, the price of the device is significantly less than other devices with materials costing less than $55 and having a simpler design than predicate devices. Lastly, fatigue should be considerably less than conventional CPR because this device moves muscle work to larger muscles groups such and the quadriceps with the opportunity to switch legs in case of fatigue because of the device design. In the near future, further testing will determine the cuff’s applied force to the torso as well as the effectiveness of compressions. In addition, custom foot pump and cuff designs will be developed and alternative materials and tubing to connect the components to increase cyclic frequency will be considered. References 1. AHA CPR Facts and Statistics. http: //www. americanheart. org/ 2. Abella BS, Sandbo N, et al. Chest compression rates during cardiopulmonary resuscitation are suboptimal: a prospective study during in-hospital cardiac arrest. Circulation. 2005; 111: 428– 434. 3. 2005 American Heart Association Guidelines for CPR. http: //circ. ahajournals. org/content/vol 112/24_suppl/ 4. CPR Instructions Should Focus On Continuous Chest Compressions. Science Daily. 6 May 2005. 5. Halperin, H. R. , et al. A Preliminary Study of Cardiopulmonary Resuscitation by Circumferential Compression of the Chest with Use of a Pneumatic Vest. New England Journal of Medicine. 1993; 329: 762 -768. Acknowledgments Thanks to the generous gift of Drs. Hal Wrigley and Linda Baker, the Bio. Engineering Department, and Dr. Menegazzi.