A blood pressure-related profile extracted from pig left vagus nerves using cuff electrodes

Abstract

Vagus nerve (VN) stimulation (VNS) is used in epilepsy and tested for blood pressure (BP) control. Whereas the present VNS methods are scheduled, closed-loop VNS (CL-VNS) may be safer and more efficient. However, CL-VNS for epilepsy and BP control require implantable means to monitor seizures and BP changes and such means are not available yet. It is known that the VN conducts afferent BP-related signals, and that seizures are often preceded by BP changes. This study was performed to investigate if such BP-related signals can be recorded using implantable means and if information regarding BP changes can be derived from such recordings. The experiments were performed in two pigs subjected to adrenaline administration for BP increase. The left VN electroneurogram (VENG) was recorded using cuff electrodes, the BP using carotid catheters and the ECG using surface electrodes. By ensemble averaging the VENG activity relative to the R-peaks, afferent BP-related VENG profiles (BP-VENGs) were extracted from the VENG. The BP-VENGs were morphologically similar, proportional and in phase with the carotid BP pulses. The maximum amplitude of those profiles was used to derive a phasic VENG component (pVENG) which changed proportional to the mean BP changes. It is concluded that the BP-VENGs and pVENG could eventually be implemented in CL-VNS for epilepsy and BP control to monitor BP changes and modulate on-demand VNS.