Muzquiz Maria Ivette, Richardson Lindsay, Vetter Christian, Smolik Macallister, Alhawwash Awadh, Goodwill Adam, Bashirullah Rizwan, Carr Michael, Yoshida Ken
Department of Biomedical Engineering, Indiana University - Purdue University Indianapolis, Indianapolis, USA.
Department of Biology, Indiana University - Purdue University Indianapolis, Indianapolis, USA.
Bioelectron Med. 2021 Jun 30;7(1):9. doi: 10.1186/s42234-021-00072-w.
This paper describes a method to reversibly block nerve conduction through direct application of a 1 Hz sinusoidal current waveform delivered through a bipolar nerve cuff electrode. This low frequency alternating current (LFAC) waveform was previously shown to reversibly block the effects of vagal pulse stimulation evoked bradycardia in-vivo in the anaesthetised rat model (Mintch et al. 2019). The present work measured the effectiveness of LFAC block on larger caliber myelinated vagal afferent fibers in human sized nerve bundles projecting to changes in breathing rate mediated by the Hering-Breuer (HB) reflex in anaesthetized domestic swine (n=5).
Two bipolar cuff electrodes were implanted unilaterally to the left cervical vagus nerve, which was crushed caudal to the electrodes to eliminate cardiac effects. A tripolar recording cuff electrode was placed rostral to the bipolar stimulating electrodes on the same nerve to measure changes in the compound nerve action potentials (CNAP) elicited by the vagal pulse stimulation and conditioned by the LFAC waveform. Standard pulse stimulation was applied at a sufficient level to induce a reduction in breathing rate through the HB reflex. If unblocked, the HB reflex would cause breathing to slow down and potentially halt completely. Block was quantified by the ability of LFAC to reduce the effect of the HB reflex by monitoring the respiration rate during LFAC alone, LFAC and vagal stimulation, and vagal stimulation alone.
LFAC achieved 87.2 ±8.8% block (n=5) at current levels of 1.1 ±0.3 mA (current to peak), which was well within the water window of the working electrode. CNAP showed changes that directly correlated to the effectiveness of LFAC block, which manifested itself as the slowing and amplitude reduction of components of the CNAP.
These novel findings suggest that LFAC is a potential alternative or complementary method to other electrical blocking techniques in clinical applications.
本文描述了一种通过双极神经袖套电极施加1Hz正弦电流波形来可逆性阻断神经传导的方法。先前已证明这种低频交流电（LFAC）波形可在麻醉大鼠模型中可逆性阻断迷走神经脉冲刺激诱发的心动过缓效应（Mintch等人，2019年）。本研究测量了LFAC阻断对麻醉家猪（n=5）中投射到由黑林-布雷尔（HB）反射介导的呼吸频率变化的较大直径有髓迷走传入纤维的有效性。
将两个双极袖套电极单侧植入左颈迷走神经，在电极尾侧进行压榨以消除心脏效应。在同一神经上，将一个三极记录袖套电极置于双极刺激电极的头侧，以测量由迷走神经脉冲刺激诱发并由LFAC波形调节的复合神经动作电位（CNAP）的变化。以足够的水平施加标准脉冲刺激，以通过HB反射诱导呼吸频率降低。如果不被阻断，HB反射会导致呼吸减慢并可能完全停止。通过监测单独的LFAC、LFAC和迷走神经刺激以及单独的迷走神经刺激期间的呼吸频率，以LFAC降低HB反射效应的能力来量化阻断效果。
在1.1±0.3mA（电流峰值）的电流水平下，LFAC实现了87.2±8.8%的阻断（n=5），这完全在工作电极的水窗范围内。CNAP显示出与LFAC阻断效果直接相关的变化，表现为CNAP成分的减慢和幅度降低。
这些新发现表明，在临床应用中，LFAC是其他电阻断技术的潜在替代或补充方法。
