Abstract Body:
Introduction: Developing multi-modal cardiopulmonary resuscitation (CPR) in animal models of cardiac arrest is challenging because of the exponential increase in the number of possible combinations of n modalities. As the number of modalities under investigation increases the number of studies necessary become unwieldy. To mitigate this issue, we have considered two methodologic approaches: 1) a variant of the n-of-1 design in which we divide experiments into time-limited epochs with alternating treatment pairs, and 2) using the changes (delta) in perfusion pressures across epochs as the hemodynamic variable. However, the temporal dynamics of perfusion pressures during the alternation of CPR modes remains poorly investigated so the optimal epoch length remains unknown.

Hypothesis: After changes in CPR efficacy, changes in perfusion pressures reach their new plateau rapidly, allowing for relatively short experimental epochs.

Methods: In a porcine model of VF (n=6), we compared standard circumferential constriction CPR (CC-CPR) with and without interposed abdominal counterpulsation (IAC-CPR). Both treatments were administered by a custom circumferential pneumatic system. Alternating 30-second epochs of each treatment were performed. Aortic (Ao) and Right Atrial (RA) pressures were measured via micromanometer catheters, and coronary perfusion pressures (CPP) were calculated.

Results: IAC-CPR Ao trended upwards after each change from standard CC-CPR to IAC-CPR. (See Fig.) However, it didn’t reach a clear plateau in 30 sec.

Conclusions: Relatively short experimental epochs, with changes in hemodynamic indicators as the basis for study, appear to be a promising approach to limited experimental populations. After changing to a CPR therapy of different effectiveness, Ao begins to increase relatively rapidly but does not reach its new equilibrium within 30 sec. So longer experimental epochs may be needed. Additionally, these observations have important implications for the development of new combination CPRs and the application of precision “play the winner” algorithms during actual clinical use.