Walcott Gregory P, Booker Robert Sylvester, Ideker Raymond E
University of Alabama at Birmingham, 1530 3rd Ave So., Volker Hall B140, 35294-0019, USA.
Theracardia Inc., San Clemente, CA, USA
Resuscitation. 2002 Dec;55(3):301-7. doi: 10.1016/s0300-9572(02)00212-5.
This study examined (1) the defibrillation efficacy of using a minimally invasive direct cardiac massage (MID-CM) device as one electrode of the defibrillation electrical circuit and (2) the effect on external defibrillation of defibrillating when the MID-CM device is in place and a pneumothorax is present.
Part 1: in seven pigs, defibrillation thresholds (DFTs) were determined with a truncated exponential biphasic waveform. DFTs were determined for five electrode configurations: standard transthoracic defibrillation with electrodes on the left and right chest walls (1), with the MID-CM as one of the defibrillation electrodes pressed gently (2) or firmly (3) against the heart with the right chest wall patch as the second electrode, the same as (1) with the MID-CM device in place and the lungs at end-inspiration (4) or at end-expiration (5). Part 2: in six pigs, DFTs were determined with a monophasic damped sinusoidal waveform with external defibrillation electrodes (1) and with the device as one defibrillation electrode and the other electrode on either the anterior (2), lateral (3), or posterior right chest wall (4).
Part 1: the DFTs for (2) or (3) were not different (18.7+/-12.4 vs. 17.0+/-8.3 J), but both DFTs were lower than that for (1) (155+/-45 J). The DFT was elevated for (4) (205+/-69 J) compared with (1). For (5) only one animal could be defibrillated with shocks up to 360 J. Part 2: the DFTs for (2), (3) or (4) were not different (19.5+/-11.0, 25.4+/-9.4, 27.4+/-9.0 J), but all three were lower than the DFT for (1) (198+/-70 J).
Using the MID-CM device as one electrode of the defibrillation circuit markedly lowers the DFT compared with that for standard transthoracic defibrillation for both a monophasic and biphasic waveform. Defibrillation with the device in place and the chest opened elevates the DFT for external defibrillation much more during end-expiration than during end-inspiration.
本研究考察了（1）使用微创直接心脏按压（MID-CM）装置作为除颤电路的一个电极时的除颤效果，以及（2）当MID-CM装置就位且存在气胸时，其对体外除颤的影响。
第一部分：在7头猪中，采用截断指数双相波测定除颤阈值（DFT）。针对5种电极配置测定DFT：在左、右胸壁放置电极进行标准经胸除颤（1）；以MID-CM作为一个除颤电极，轻轻（2）或用力（3）按压心脏，右胸壁贴片作为第二个电极；与（1）相同，但MID-CM装置就位且肺处于吸气末（4）或呼气末（5）。第二部分：在6头猪中，采用单相阻尼正弦波，通过体外除颤电极（1）以及将该装置作为一个除颤电极，另一个电极置于右前胸壁（2）、外侧胸壁（3）或后胸壁（4）来测定DFT。
第一部分：（2）或（3）的DFT无差异（18.7±12.4 J对17.0±8.3 J），但两者均低于（1）的DFT（155±45 J）。与（1）相比，（4）的DFT升高（205±69 J）。对于（5），仅1只动物能被高达360 J的电击除颤。第二部分：（2）、（3）或（4）的DFT无差异（19.5±11.0、25.4±9.4、27.4±9.0 J），但这三者均低于（1）的DFT（198±70 J）。
与标准经胸除颤相比，将MID-CM装置作为除颤电路的一个电极，对于单相和双相波形而言，均能显著降低DFT。当装置就位且胸腔打开时进行除颤，呼气末时体外除颤的DFT升高幅度比吸气末时大得多。
