Abstract P43: A Hemodynamic Study of Hybrid Mechanical Chest Compression Patterns, Discriminating the Effect of Accelerated Compression from Accelerated Decompression in a Porcine Model of Cardiac Arrest
Introduction: Effective chest compressions to reestablish sufficient cerebral and coronary perfusion are crucial during cardiac arrest. Piston based mechanical chest compression devices deliver accelerated compressions and decompressions, resulting in superior hemodynamics compared to manual compression in animal studies. We have, in a porcine model of cardiac arrest, compared the hemodynamic effects of two different hybrid compression patterns with a standard pattern used in modern mechanical chest compression devices.
Methods: In 12 anesthetized domestic pigs in ventricular fibrillation, we monitored coronary perfusion pressures (CPP), cerebral cortical blood flow (CCBF), and cardiac function using transesophageal echocardiography (TEE). Three chest compression curves with similar rate and depth were tested in randomized crossover experiments using a custom build servo controlled mechanical chest compression device. Two hybrid compression curves, one with accelerated trapezoid compression and sinusoidal decompression (TrS), and one with sinusoidal compression and accelerated trapezoid decompression (STr), were tested against a standard accelerated trapezoid compression/decompression pattern (TrTr). Statistical comparisons were done with paired t tests and data presented as difference in means with 95% CI.
Results: We found 7% (1, 14, p=0.046) lower CCBF and a 3 mmHg (1, 5, p=0.017) reduction in CPP with the TrS method compared to TrTr, whereas there were only non-significant reduction in CCBF, 6% (−3, 15, p=0.176), with the STr method compared to TrTr, and no difference in CPP, 0 mmHg (−2, 3, p=0.703). TEE imaging revealed that direct cardiac compression was the major mechanism generating forward blood flow in our experimental model.
Conclusion: Both cardiac and cerebral perfusion benefited from rapid decompression, while rapid compression in itself caused no significant improvement in hemodynamics. The evolution of mechanical CPR is dependent on further exploring the physiology behind forward blood flow during external chest compressions.