Department of Biomedical Engineering and Imaging Medicine, Army Medical University, 30 Gaotanyan Main Street, Chongqing, 400038, China.
Department of Emergency, Southwest Hospital, Army Medical University, Chongqing, 400038, China.
Sci Rep. 2021 Jan 15;11(1):1586. doi: 10.1038/s41598-020-80521-9.
Defibrillation is accomplished by the passage of sufficient current through the heart to terminate ventricular fibrillation (VF). Although current-based defibrillation has been shown to be superior to energy-based defibrillation with monophasic waveforms, defibrillators with biphasic waveforms still use energy as a therapeutic dosage. In the present study, we propose a novel framework of current-based, biphasic defibrillation grounded in transthoracic impedance (TTI) measurements: adjusting the charging voltage to deliver the desired current based on the energy setting and measured pre-shock TTI; and adjusting the pulse duration to deliver the desired energy based on the output current and intra-shock TTI. The defibrillation efficacy of current-based defibrillation was compared with that of energy-based defibrillation in a simulated high impedance rabbit model of VF. Cardiac arrest was induced by pacing the right ventricle for 60 s in 24 New Zealand rabbits (10 males). A defibrillatory shock was applied with one of the two defibrillators after 90 s of VF. The defibrillation thresholds (DFTs) at different pathway impedances were determined utilizing a 5-step up-and-down protocol. The procedure was repeated after an interval of 5 min. A total of 30 fibrillation events and defibrillation attempts were investigated for each animal. The pulse duration was significantly shorter, and the waveform tilt was much lower for the current-based defibrillator. Compared with energy-based defibrillation, the energy, peak voltage, and peak current DFT were markedly lower when the pathway impedance was > 120 Ω, but there were no differences in DFT values when the pathway impedance was between 80 and 120 Ω for current-based defibrillation. Additionally, peak voltage and the peak current DFT were significantly lower for current-based defibrillation when the pathway impedance was < 80 Ω. In sum, a framework of adjusting the charging voltage and shock duration to deliver constant energy for low impedance and constant current for high impedance via pre-shock and intra-shock impedance measurements, greatly improved the defibrillation efficacy of high impedance by lowering the energy DFT.
除颤通过足够的电流通过心脏来终止心室颤动（VF）。尽管已经证明基于电流的除颤比单相波形的基于能量的除颤优越，但具有双相波形的除颤器仍将能量用作治疗剂量。在本研究中，我们提出了一种基于 transthoracic impedance（TTI）测量的新型基于电流的双相除颤框架：根据能量设置和测量的预冲击 TTI 调整充电电压以输送所需电流；并根据输出电流和冲击内 TTI 调整脉冲持续时间以输送所需能量。在模拟的 VF 高阻抗兔模型中比较了基于电流的除颤与基于能量的除颤的除颤效果。通过在 24 只新西兰兔（10 只雄性）的右心室起搏 60 s 来诱导心脏骤停。在 VF 后 90 s 应用两种除颤器之一进行除颤冲击。利用 5 步升序方案确定不同路径阻抗下的除颤阈值（DFT）。间隔 5 min 后重复该程序。对每个动物进行了 30 次纤维性颤动事件和除颤尝试的研究。与基于能量的除颤相比，基于电流的除颤器的脉冲持续时间明显更短，波形倾斜度更低。与能量型除颤相比，当路径阻抗>120Ω时，能量，峰值电压和峰值电流 DFT 明显降低，但当路径阻抗在 80 至 120Ω之间时，基于电流的除颤的 DFT 值没有差异。此外，当路径阻抗<80Ω时，基于电流的除颤的峰值电压和峰值电流 DFT 明显降低。总之，通过预冲击和冲击内阻抗测量来调整充电电压和冲击持续时间，以输送低阻抗恒定能量和高阻抗恒定电流的框架，通过降低能量 DFT，大大提高了高阻抗的除颤效果。
