Abstract Body: 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.