Coronary perfusion pressure during external chest compression in pseudo-EMD, comparison of systolic versus diastolic synchronization.

Background: The fraction of cardiac arrest patients presenting with pulseless electrical activity is increasing, and it is likely that many of these patients have pseudo-electromechanical dissociation (P-EMD), a state in which there is residual cardiac contraction without a palpable pulse. The efficacy of cardiopulmonary resuscitation (CPR) with external chest compression synchronized with the P-EMD cardiac systole and diastole has not been fully evaluated.

Hypothesis: During external chest compression in P-EMD, the coronary perfusion pressure (CPP) will be greater with systolic synchronization compared with diastolic phase synchronization.

Methods: A porcine model of P-EMD induced by progressive hypoxia with peak aortic pressures targeted to 50 mmHg was used. CPR chest compressions were performed by either load distributing band or vest devices. Paired 10s intervals of systolic and diastolic synchronization were performed randomly during P-EMD, and aortic, right atrial and CPP were compared.

Results: Stable P-EMD was achieved in 8 animals, with 2.6±0.5 matched synchronization pairs per animal. Systolic synchronization was association with increases in relaxation phase aortic pressure (41.7±8.9 mmHg vs. 36.9±8.2 mmHg), and coronary perfusion pressure (37.6±11.7 mmHg vs. 30.2±9.6 mmHg). Diastolic synchronization was associated with an increased right atrial pressure (6.7±4.1 mmHg vs. 4.1±5.7 mmHg).

Conclusion: During P-EMD, synchronization of external chest compression with residual cardiac systole was associated with higher CPP compared to synchronization with diastole.