Influence of the percutaneous closed-loop auricular vagus nerve stimulation on the mutual interplay of respiration and heart rate variability: systolic vs. diastolic gated stimulation

Abstract

The medical approach of stimulating the Vagus Nerve (VNS) opens various possibilities for innovative therapeutic interventions by leveraging the intricate neural pathways to modulate autonomic functions and potentially enhance physiological responses. To be able to induce the VN more efficiently, it is important to better understand the physiological basics of VN stimulation and its different patterns. Further, it is essential to analyze its impact on the sympathovagal balance - the dynamic interplay between the sympathetic and parasympathetic nervous system, influencing regulation of various physiological processes within the body and therefore playing a crucial role in maintaining a healthy autonomic nervous system. This study investigates the comparative impacts of percutaneous auricular Vagus Nerve Stimulation (aVNS) synchronized on the personal level with the cardiac cycle - specifically inducing impulses during systole versus during diastole - on respiratory and cardiovascular dynamics. The research methodology is based on three main phases: enlightening theoretical foundations, describing the setup of acquisition of data and presenting a detailed data analysis. Each participant of this study underwent comprehensive sessions of data collection involving measurements of respiratory curve, electrocardiogram (ECG) data and blood pressure measurements. Subsequent data analysis aimed to show the effects of synchronized percutaneous aVNS on individual subject's median respiratory curves and the changing patterns of RR-interval lengths during the respiratory cycle. Differences in curves between the two stimulation scenarios were examined and compared against a control dataset from the same individuals without aVNS. The motivation behind this investigation was to analyze potential alterations in respiratory curves and changes in heart rate variability (HRV) between the different scenarios. High HRV is crucial for the body to adapt to changing parameters naturally, maintaining an essential cardiovascular equilibrium. The primary aim was to elucidate the distinct effects of the two synchronized cardiac rhythm-based scenarios to facilitate targeted applications of percutaneous aVNS in treating various physiological issues. Repeating deviations and patterns were observed within the obtained data of the curves of the median progressions of respiratory curves and variations of RR-intervals for the two scenarios. They were detected for most of the individual curves of respiration and HRV per subject and also for the superimposed curves of all the subjects per set, when comparing the data of non-aVNS with the data of systolic- and diastolic-gated stimulation of the VN. Although interpretation may vary due to heterogeneous subject responses, overall trends in the curves were visualized. This study aims to contribute valuable insights to the field, enabling future refinements in the personalized aVNS application.