| Abstract [eng] |
Stress affects more people each year negatively influencing their quality of life. Stress should not be considered just as a personal problem, the costs associated by increasing stress levels are a burden to employers and heath care facilities. Common ways to reduce stress levels are meditation and mental preparation techniques, and while in some cases these methods can help, they are not fully effective or easy to implement. Increasing understanding of human biology provides more information about the connections between emotional states and physiological parameters. It is now known that stress affects the heart, sweat glands and numerous more bodily systems. Additionally, connections between these systems and biological structures of the body have been found, and it is shown that manipulation of biological structures can influence physiological parameters. This work analyses the effects of thermal stimulation of a biological structure, vagus nerve, on changes of physiological parameters related to stress. To achieve this goal a device was made allowing real time control of thermal stimulation, that is implemented using Peltier elements. In order to test the changes of stress parameters a study protocol was created allowing the collection of calm and stressed state data. The study itself was performed on 12 participants and the changes of heart rate variability, electrodermal activity and photopletizmography parameters were calculated. When analyzing heart rate variability parameters, it was found that heart rate, the energy of high frequency band, total energy and the ratio of low and high energy changed between calm and stressed states. Electrodermal activity analysis results showed that all parameters associated with this measurement changed significantly between the two analyzed psychological states. Photopletizmography parameter analysis showed that data from 2 of 5 different light emitting diodes showed changes between calm and stressed states. When analyzing the effects of thermal stimulation between identical parts of the study, the only difference being the effect of stimulation or lack of thereof, changes in measured parameters were observed. Three parameters: the low band energy and the ratio of low and high band energy of heart rate variability, and the mean value of electrodermal activity changed when comparing thermally stimulated and non-stimulated periods. These differences were the same as the ones observed in the comparison of calm and stressed states, if stimulated timeframe is equated to calm state and non-stimulated timeframe is equated to stress state. This means that thermal stimulation affected some of the analyzed parameters in a way that indicates a reduction of stress level. |
