Objective: The two objectives of this report are: first, to describe a comparison of chest compressions unsynchronized or synchronized to native cardiac activity in a porcine model of hypotension, and second, to develop an algorithm to provide synchronized chest compressions throughout a range of native heart rates likely to be encountered when treating PEA cardiac arrest. Methods: We adapted our previously developed signal-guided CPR system to provide compressions synchronized to native electrical activity in a porcine model of hypotension as a surrogate of PEA arrest. We describe the first comparison of unsynchronized to synchronized compressions in a single animal as a proof-of-concept. We developed an algorithm to provide optimal synchronized chest compressions regardless of intrinsic PEA heart rate while simultaneously maintaining the chest compression rate within a desired range. We tested the algorithm with computer simulations measuring the proportion of intrinsic and compression beats that were synchronized, and the compression rate and its standard deviation, as a function of intrinsic heart rate and heart rate jitter. Results: We demonstrate and compare unsynchronized versus synchronized chest compressions in a single porcine model with an intrinsic rhythm and hypotension. Synchronized, but not unsynchronized, chest compressions were associated with increased blood pressure and coronary perfusion pressure. Our synchronized chest compression algorithm is able to provide synchronized chest compressions to over 90% of intrinsic beats for most heart rates while maintaining an average compression rate between 90 and 140 compressions per minute with relatively low variability. Conclusions: Synchronized chest compression therapy for pulseless electrical rhythms is feasible. A high degree of synchronization can be maintained over a broad range of intrinsic heart rates while maintaining the compression rate within a satisfactory range. Further investigation to assess benefit for treatment of PEA is warranted.
Keywords: PEA; chest compressions; pulseless electrical activity; swine; synchronized.