Quantificação de limiares térmicos em fibras finas

• Ano de defesa: 2012
• Autor(a) principal: Denny Daniel Collina
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Sincronização e dessincronização; Teste quantitativo de sensibilidade térmica; QST-T; EEG; Módulo de Peltier; Fibras finas; Estimulação térmica; Engenharia elétrica
• Link de acesso: http://hdl.handle.net/1843/BUOS-9VEMLM

The afferent input of thermal stimuli and pain to the central nervous system is carried by myelinated (Aä) and non-myelinated (C) fine fibers, which have been studied up to this point. An important contribution to this study was given in the 70s, with the introduction of computer-aided devices for thermal stimulation. Since then, various devices for thermal stimulation have been developed, for either scientific research or clinical medicine. For the most part, they use Peltier module as active element. Those developed for research, usually, have restricted use. However, some devices have been developed for clinical medicine and are commercially available. They have closed architecture, with restrictions to be reconfigured and reset. This works initial proposal consists in the development of a thermal stimulation device (Biostimulator), based on Peltier module, portable and easy to reset, to allow the implementation of stimulation protocols either already known or still to be created. Afterwards, the device will be used in the assessment of the correlation between moderated thermal stimulation, along the lines of the tests of determination of heat and cold perception thresholds, and the brain activity alteration, through the analysis of EEG signals. During the development of the Biostimulator a laptop computer was used, connected through USB cable to a signal acquisition board, using LabView®s virtual instrumentation environment, which makes use of a user-friendly graphic interface, as well as processing functions for temperature control, signal acquisition management and storage of signals. In addition to the stimulation by pulses with linear ascent, the stimulation was implemented with three waveforms: sinusoidal, triangular and trapezoidal. The sinusoidal waveform presented harmonic distortion of 6.4%, and the triangular and trapezoidal waveforms presented slight distortions in their inflexion points. Three virtual instruments were implemented for the Biostimulator: the Instrument of Development allowed the testing of the data acquisition and the operation, the adjustment of the temperature controlling device, the implementation and testing of the generation of varied waveforms and the storage of data. The instrument of the Method of Limits allowed the performing of initial tests for the determination of the sensitivity in volunteers. At last, the instrument of the Sensitivity Test with Test Tubes made it possible to study the quantification of the thermal stimulation promoted by this method. The performance of such tests, with totally different protocols, evidences the Biostimulators versatility. The study of the correlation between moderated thermal stimulation, as well as the alteration in the brain activity for rhythms ä, è, á, â and ã, was performed with 11 volunteers and made use of a new stimulation protocol, which, in one cycle, uses heating and cooling stimuli, interspersed with intervals of application of basal temperature (32°C). The new protocol showed an increase of energy at rhythm á, with peak at 9.4 Hz, in response to moderated heating, while it was not possible to detect response to moderated cooling.