AUSCULTATION OF A HEART AND VASCULAR ACTIVITY DURING AURICULAR NERVE STIMULATION

The principal objective of the research was to develop and test a multichannel system intended to capture heart (PCG) and Korotkoff sound (KS) signals in a human model of transcutaneous auricular nerve stimulation (tANS). In particular, the purpose was to develop contact auscultation transducers (transducers) capable of capturing PCG and KS at standard auscultation positions without and during the selective tANS. The scope was to develop transducers capable of capturing body sounds lying in a portion of the frequency spectrum between 20 Hz and 200 Hz. They should be as insensitive as possible to external sound or ambient noise and should be capable of compensating for friction noise due to body movements. The system developed consisted of five transducers, where four of them were intended for the auscultation of PCG generated by heart valves, while one of them was intended to capture KS. The functionality of the transducers was tested in the female model by applying four of transducers to the standard positions on the chest and one over the Brachial artery. The results show that the system developed was highly sensitive to PCG and KS, and less sensitive to external ambient sounds and friction noise. Namely, the S1 and S2 heart-sound peaks are present clearly in the recorded PCG signal as well as during the tANS. It was also shown that during the tANS, heart cycles became slightly shorter and, thus, the heart rhythm slightly higher. Finally, during the tANS, both heart sounds S1 and S2 became louder. In conclusion, the findings provide some evidence that the sounds captured by the transducers emanate from the organs under study and are related to their activity and tANS.