Abstract Body: Background:
The efficacy of different conventional ventilation during automated head-up (AHUP) CPR using active decompression and impedance threshold device with head and torso elevation is unknown. We sought to determine the central and peripheral hemodynamics while using the 10:1 versus the 30:2 positive pressure ventilation (PPV).
Research Question:
Does the PPV delivery method affect the hemodynamics during AHUP-CPR?
Methods:
Ventricular fibrillation was induced in anesthetized pigs (n=5), followed by AHUP-CPR initiation with positive pressure ventilations applied using an automated bag compressor to deliver 10ml/kg of tidal volume over 1 sec at a rate of 10 breaths/min. After 15 minutes of CPR using a 10:1 ratio, ventilation was changed to a 30:2 ratio for 2 minutes with 2 PPV delivered consecutively. Thereafter 10:1 ratio was resumed followed by another 2-minute round of 30:2 PPV mode. Intraventricular pressures and volumes using conductance catheters placed in the right ventricle (RV), along with other hemodynamic parameters were recorded continuously, during the 2-minute intervals between PPV delivery. A mixed-effects model was used to evaluate the effects of PPV mode on pressure-volume (PV) loop parameters while using a Spearman correlation to explore the relationship between PV loop indices.
Results:
There was no statistically significant difference between RV stroke volume (SV) with 10:1 versus 30:2 PPV mode (Table 1). Throughout 2 minutes, 30:2 ventilation mode resulted in a significantly higher end-tidal CO2 (ETCO2), and higher pressures with a higher pulmonary elastance (Ea) imposed on RV (p<0.05). Higher Ea was strongly correlated with lower SV and ETCO2 (Spearman's rho correlation confidence of -0.97 and -0.83, respectively). No significant differences were observed between the two ventilation modes in any other hemodynamic parameters, including intrathoracic, aortic and right atrial pressures, as well as coronary and cerebral perfusion pressures.
Conclusion:
No significant difference was found for right ventricular stroke volume when comparing one breath after 10 chest compressions to two breaths after 30 compressions during automated head-up CPR. Delivering two consecutive breaths after 30 continuous compressions led to an overall higher ETCO2, but it also imposed greater ventricular pressure and afterload, which were significantly correlated with reduced SV and ETCO2.