Abstract 262: Hemodynamically-Guided Optimum Chest Compression Point in a Rat Model of Cardiopulmonary Resuscitation

Abstract

Introduction: CPR aims to re-establish blood flow by chest compression (CC), achieving threshold levels of coronary perfusion pressure (CPP). For this, current guidelines recommend the lower sternal half as optimum CC point. However, this point might be not optimal for every individual. We investigated the hemodynamics generated by CC performed on different chest points in a rat model of CPR. We hypothesized that a CC point hemodynamically-identified would be a better approach compared to the lower sternal half. Methods: Ten male rats were anesthetized and arterial and right atrial pressures monitored. Ventricular fibrillation was induced and untreated for 8 min. CPR, including mechanical CC, ventilation, and epinephrine, was then performed for 8 min. Animals were divided to receive CC performed either on the lower sternal half (standard (STD), n=5) or on an optimum point identified as the one able to generate the maximum CPP (MaxCPP group, n=5). Cardiac districts involved in CC were subsequently identified by computed tomography (CT). Results: STD CC produced a CPP that was constantly below the threshold for successful resuscitation and trended to decrease over time. When the optimum CC point was identified hemodynamically, the CPP generated was constantly > 20 mmHg. Indeed, CPP was significantly higher in the MaxCPP group compared to the STD one for the whole 8 min of CPR (p<0.01, Fig). Moreover, administration of epi rapidly further improved CPP (p<0.01 vs. pre-epi) in the group with an optimized CC point, while no drug effect was observed in the STD one. CT scan showed that the lower sternal half did not correspond to the LV maximum diameter, known to account for a maximum stroke volume generation during CC (Fig). Conclusion: Standard lower sternal half CC point is not able to maximize hemodynamics during CPR, making ineffective CC efforts and vasopressor administration. The quality of CPR may improve if the optimum CC point is identified as a reflection of CPP generated.