Intraventricular Pressure and Volume during Conventional and Automated Head-up CPR.

Background: Active compression-decompression (ACD) CPR, an impedance threshold device (ITD) and automated head and thorax elevation, collectively termed AHUP-CPR, increases cerebral and coronary perfusion pressures, brain blood flow, end-tidal CO2 (ETCO2) and cerebral oximetry (rSO2) in animal models compared with conventional (C) CPR. We tested the hypothesis that cardiac stroke volume (SV) is higher with AHUP-CPR versus C-CPR or ACD+ITD in a porcine cardiac arrest model.

Methods: Farm pigs (n=14) were sedated, anesthetized, and ventilated. Hemodynamics, including biventricular pressure-volume loops, were continuously measured. Following 10 minutes of untreated ventricular fibrillation, C-CPR was performed for 2 minutes, then ACD+ITD for 2 minutes in the flat position, then AHUP-CPR thereafter. Linear mixed-effects model and Pearson correlation comparisons were used for statistical analysis.

Results: Coronary and cerebral perfusion pressures, ETCO2, rSO2, and right (RV) and left (LV) ventricular SV increased progressively and significantly with the implementation of AHUP-CPR (p<0.05). RV SV with C-CPR was 24.8 ± 2.8 mL (∼48% of baseline) versus 45.2 ± 4.1 with AHUP-CPR (∼90% of baseline) (p<0.01). LV SV with C-CPR was 17.6 ± 1.8 mL (∼35% of baseline) versus 38.7 ± 6.7 with AHUP-CPR (∼80% of baseline) (p<0.01).

Conclusion: A fundamental and inherent shortcoming of C-CPR, limited cardiac stroke volume, and resultant forward flow, can be overcome with AHUP-CPR. These findings may help explain the better outcomes associated with early use of AHUP-CPR.