Utvärdering av upplevd tolerans och komfort vid olika vibrationer i vibrotaktil taVNS

Vagus nerve stimulation (VNS) is a therapy providing stimulation to the vagus nerve by electricity. The therapy is currently approved by FDA and EMA as treatment for epilepsy and depression. Transcutaneous auricular vagus nerve stimulation (taVNS) is a branch of VNS that stimulate the vagus nerve with non-invasive equipment through the ear. TaVNS has been proven to have beneficial health effects and usage in treatment of various medical conditions. Electricity is commonly used in taVNS research but the use of vibrations for VNS is getting more popular. This study aims to create a vibrotactile taVNS device and investigate wether it is comfortable for use as it is producing vibrations directly to the ear. In order to achieve this goal an in-ear wearable with an attached vibration element together with a system controlling the vibration was designed and created. The in-ear wearable was designed by creating a molding of the external ear, modifying and 3D printing it. An eccentric rotating mass motor was attached to the wearable and used as vibration element. A script uploaded to an appropriate PCB together with a smartphone application was programmed to control the motor wirelessly. Pulse Width Modulation (PWM) signal with different duty cycles was used to change the voltage driving the motor at different rotational speeds. The change in duty cycle and the effect on the motor was analyzed. Lastly, 7 different vibrations for the taVNS was used on 9 volunteers and their perceived comfort and tolerance towards the vibrations were studied. The result showed that all tested vibrations had some degree of discomfort involved. Only one vibration intensity was tolerable by the majority of subjects but not all of them. The vibration produced by the lowest average voltage and regulated by the lowest duty cycle of PWM signal was deemed to be least discomfortable and more preferred. These findings give insight as to wether vibration used in taVNS is appropriate or not. As the result show, vibrotactile taVNS is discomfortable and not tolerable for high levels of vibration intensities. Before continuing research on vibrotactile taVNS relevence for treatments, mappings between vibration frequency and amplitude towards perceived comfort should be done. This will give insight as to which vibration intensities are appropriate for taVNS use.