Abstract
BACKGROUND: Current guidelines recommend a 50 mm or greater compression depth for manual chest compression in adults. However, whether this uniform compression depth is a suitable requirement for mechanical CPR remains to be determined. We hypothesized that a relatively shallow compression depth (30 mm) would have similar hemodynamic efficacy but fewer complications versus the standard compression depth (50 mm) during mechanical cardiopulmonary resuscitation (CPR) with the miniaturized chest compressor (MCC) in a porcine model. METHODS: In the current study, we used a total of 16 domestic male pigs (38±2 kg). All pigs were exposed to 7 min of ventricular fibrillation (VF) followed by 5 min of CPR. Then the animals were randomly assigned to the shallow (30 mm) group and the standard (50 mm) group. At the second min of CPR, every pig was given epinephrine (20 µg/kg) through the femoral vein and repeated every 3 min. First defibrillation was delivered with a single 120 J shock at 5 min of CPR. Hemodynamics, carotid blood flow (CBF), end-tidal carbon dioxide (ETCO(2)), coronary perfusion pressure (CPP), intrathoracic pressure (ITP) and arterial blood gas were measured. Rib fractures and lung injuries, as indicated by ground-glass opacification (GGO), as well as intense parenchymal opacification (IPO), were assessed and calculated by quantitative computed tomography (QCT) scan. RESULTS: We found no significant differences in CPP, CBF, or ETCO(2) between the both groups throughout the CPR period. After administration of epinephrine, the CPP of all animals increased while ETCO(2) and CBF decreased during CPR. A significantly lower intrathoracic positive pressure (ITPP) and systolic artery pressure (SAP) were measured in the shallow group at the first min of CPR. However, we didn't find remarkable differences in these values between the both groups for the next 4 min of CPR. All animals were successfully resuscitated. The shallow group had significantly lower IPO QCT scores compared with the standard group. We found no significant differences in GGO QCT scores after resuscitation between both groups. CONCLUSIONS: Relatively shallow compression depth has similar hemodynamic efficacy but fewer complications versus the standard compression depth.