Intraventricular pressure and volume during conventional and automated head-up CPR

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.

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

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).

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.