Comparison of standard CPR versus diffuse and stacked hand position interposed abdominal compression-CPR in a swine model

Interposed abdominal compression cardiopulmonary resuscitation (IAC-CPR) is an innovative basic life support technique requiring no mechanical adjuncts. Optimizing its performance remains a challenge. Hand-position technique over the abdomen during interposed abdominal compression (IAC) may be important. The purpose of this study was to determine if there is a difference in efficacy depending on the type of abdominal hand-position used. Two different hand positions were studied: open hands, placed side by side, resulting in diffuse abdominal compression and stacked hands, with one on top of the other, producing a more focal compression of the abdomen. Thirty swine were cannulated with micromanometer-tipped pressure transducers in the ascending aorta (Ao) and right atrium (RA), and Millar Doppler-tipped catheters in the descending aorta and inferior vena cava (IVC) to determine flow patterns during cardiopulmonary resuscitation (CPR), During CPR there were no differences in aortic systolic or right atrial systolic pressures. Both forms of IAC-CPR produced greater aortic diastolic and right atrial diastolic pressures then standard CPR (STD-CPR) (P<0.05). Coronary perfusion pressures (CPP), however, were not different. Blood flow directions and velocity patterns showed that STD-CPR chest compressions produce caudally directed blood flow in both the descending aorta and the IVC, and that such flows reverse (becoming cranially directed) during the relaxation phase of chest compression. IAC-CPR produced similar blood flow patterns in the aorta and IVC, as seen with STD-CPR. There were no differences in blood flow patterns between the different forms of IAC-CPR. No CPR-produced trauma difference was found. Abdominal hand position (diffuse or stacked) did not affect blood flow in either the aorta or IVC or resuscitation success in this experimental model. There was a trend towards better outcomes with stacked hands IAC-CPR with 90 versus 70% survival with STD-CPR.