Hai, Hamza

Background: Active compression-decompression (ACD) cardiopulmonary resuscitation (CPR), an impedance threshold device (ITD) and controlled, gradual, automated head and thorax elevation, collectively termed automated Head Up Position (AHUP) CPR, increases cerebral perfusion pressure (CerPP), brain blood flow, coronary perfusion pressure (CorPP), end tidal CO2 (ETCO2) and cerebral oximetry (rSO2) in animal models when compared with conventional (C) CPR. AHUP-CPR in patients is associated with increased neurologically favorable survival versus C-CPR. This study tested the hypothesis that AHUP CPR will increase cardiac stroke volume (SV) and other hemodynamics compared with C-CPR in a porcine model of cardiac arrest. Methods: Farm pigs (n=15) were sedated, anesthetized, and ventilated. Hemodynamics, including intracardiac conductance catheter based biventricular (BiV) pressure-volume (PV) loops, were continuously measured and recorded. After 10 minutes of untreated ventricular fibrillation, C-CPR was performed for 2 minutes in the supine position using an automated CPR device designed for pigs at a rate of 100 compressions/minute, depth of 21% of the chest antero-postero diameter, a 50% duty cycle, and no active decompression. ACD+ITD was then performed with 3 cm of active decompression for 2 minutes, followed by AHUP-CPR, where the head and thorax were initially raised to 10 cm and 8 cm for a 2-minute priming phase, followed by elevation over the next 2 minutes to 24 cm and 9 cm. A linear mixed-effects model with a random intercept for individual pigs was used for statistical analysis. Results: CerPP, CorPP, ETCO2, and rSO2, as well as BiV SV and cardiac output, increased progressively and significantly with implementation of AHUP-CPR (p<0.05). C-CPR generated a right ventricular (RV) SV of 25.0 mL (48% of baseline pre-VF) and left ventricular (LV) SV of 17.5 mL (39% of baseline). ACD+ITD significantly increased RV and LV SV by an average of ~ 48% versus C-CPR; AHUP-CPR further increased BiV SV by an average of ~ 83%, reaching 85% and 75% of RV and LV pre-VF values, respectively. (Figure 1) Conclusion: This study demonstrated biventricular stroke volume is significantly augmented with AHUP-CPR versus C-CPR or ACD+ITD in the flat position. These findings, together with AHUP-enhanced higher ETCO2, rSO2, and CerPP values versus C-CPR or ACD-CPR in the flat position, help explain the improved clinical outcomes associated with early use of AHUP-CPR.

Background: Active compression-decompression cardiopulmonary resuscitation (ACD-CPR) combined with an impedance threshold device (ITD) and controlled head-up positioning, collectively termed AHUP-CPR, is associated with improved outcomes compared with conventional CPR (C-CPR). Active decompression (AD) forcibly lifts the anterior chest wall with suction after each compression, while the ITD simultaneously impedes airflow into the lungs. AD and ITD synergistically lower intrathoracic pressure during decompression, improving venous return, ventricular refilling and cardiac output. Concurrently, head-up positioning lowers intracranial pressures and improves cardiac preload. This pig study focused on the physiological role of AD during AHUP-CPR, simulating real clinical scenarios. Methods: Ten male and female farm pigs (~40 kg) were anesthetized, intubated and ventilated. Hemodynamic parameters, end-tidal CO2 (ETCO2), and biventricular pressure-volume loops were recorded continuously. Ventricular fibrillation was induced and left untreated for 10 mins. Then, after 2 min of automated C-CPR in the flat position, AHUP-CPR with a 3 cm lift above the neutral position of the chest was performed for 13 min. AD was then abruptly discontinued, restarted 1 min later, and increased incrementally every min to up to 4 cm of active lift. Data were analyzed with a linear mixed-effects model, using random intercepts for individual pigs. Results: Upon cessation of AD, coronary and cerebral perfusion pressures, compression and decompression aortic pressures, compression right atrial pressure, ETCO2, right and left ventricular preload, compliance, stroke volume and cardiac output all decreased immediately and significantly (p<0.01), whereas decompression right atrial and biventricular pressures increased. With restoration of AD, physiological parameters returned to ≥ 90% of pre-AD discontinuation values (Figures 1 and 2). Conclusion: Full chest wall lift, achieved with > 3 cm of AD, was needed to maintain and optimize hemodynamics during AHUP-CPR in pigs. After pausing AD, incremental restoration of AD resulted in nearly complete restoration of peripheral and central hemodynamic measures. These observations support the benefit of and need for ≥3 cm of AD to optimize AHUP-CPR. Effective means to generate ≥3 cm of AD should be considered when implementing and developing AHUP-CPR devices to optimize outcomes.