Sevcencu Cristian, Nielsen Thomas N, Kjaergaard Benedict, Struijk Johannes J
Department of Health Science and Technology, Center for Sensory-Motor Interaction (SMI), Aalborg University, Aalborg, Denmark.
Biomedical Research Laboratory and Department of Cardiothoracic Surgery, Aalborg University Hospital, Aalborg, Denmark.
Neuromodulation. 2018 Apr;21(3):269-275. doi: 10.1111/ner.12630. Epub 2017 Jul 11.
Left vagus nerve (LVN) stimulation (LVNS) has been tested for lowering the blood pressure (BP) in patients with resistant hypertension (RH). Whereas, closed-loop LVNS (CL-LVNS) driven by a BP marker may be superior to open-loop LVNS, there are situations (e.g., exercising) when hypertension is normal. Therefore, an ideal anti-RH CL-LVNS system requires a variable to avoid stimulation in such conditions, for example, a respiratory marker ideally extracted from the LVN. As the LVN conducts respiratory signals, this study aimed to investigate if such signals can be recorded using implantable means and if a marker to monitor respiration could be derived from such recordings.
The experiments were performed in 14 anesthetized pigs. Five pigs were subjected to changes of the respiratory frequency and nine to changes of the respiratory volume. The LVN electroneurogram (VENG) was recorded using two cuff electrodes and the respiratory cycles (RC) using a pressure transducer. To separate the afferent and efferent VENGs, vagotomy was performed between the cuffs in the first group of pigs. The VENG was squared to derive respiration-related neural profiles (RnPs) and their correlation with the RCs was investigated in regard to timing and magnitude parameters derived from the two waveforms.
The RnPs were morphologically similar with the RCs and the average RnPs represented accurate copies of the average RCs. Consequently, the lung inflation/deflation RC and RnP components had the same duration, the respiratory frequency changes affected in the same way both waveforms and the RnP amplitude increased linearly with the lung inflation in all tested pigs (R values between 0.85 and 0.99).
The RnPs comprise information regarding the timing and magnitude of the respiratory parameters. As those LVN profiles were derived using implantable means, this study indicates that the RnPs could serve as respiratory markers in implantable systems.
已对左侧迷走神经（LVN）刺激（LVNS）降低顽固性高血压（RH）患者血压（BP）的效果进行了测试。然而，由血压标记物驱动的闭环LVNS（CL-LVNS）可能优于开环LVNS，在某些情况下（如运动时）高血压是正常的。因此，理想的抗RH CL-LVNS系统需要一个变量来避免在这种情况下进行刺激，例如，理想情况下从LVN提取的呼吸标记物。由于LVN传导呼吸信号，本研究旨在调查是否可以使用可植入手段记录此类信号，以及是否可以从此类记录中得出监测呼吸的标记物。
实验在14头麻醉猪身上进行。5头猪进行呼吸频率变化实验，9头猪进行呼吸量变化实验。使用两个袖带电极记录LVN神经电图（VENG），使用压力传感器记录呼吸周期（RC）。为了分离传入和传出VENG，在第一组猪的袖带之间进行迷走神经切断术。对VENG进行平方以得出与呼吸相关的神经特征（RnP），并根据从两个波形得出的时间和幅度参数研究其与RC的相关性。
RnP在形态上与RC相似，平均RnP代表平均RC的精确副本。因此，肺充气/放气RC和RnP成分具有相同的持续时间，呼吸频率变化以相同方式影响两个波形，并且在所有测试猪中，RnP幅度随肺充气呈线性增加（R值在0.85至0.99之间）。
RnP包含有关呼吸参数的时间和幅度的信息。由于这些LVN特征是使用可植入手段得出的，本研究表明RnP可作为可植入系统中的呼吸标记物。
