Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Pain is an unpleasant sensation associated with actual or potential tissue damage. Pain assessment is very important to establish the efficacy of analgesics, therapies, however, because it is a subjective experience complex and it is necessary a method that quantifies objectively. Biopotentials, such as the electromyographic signals (EMG) may aid in the study of pain. The nociceptive flexion reflex (NFR), which is observed in the biceps femoris muscle with electrical stimulation of the ipsilateral sural nerve has been used as an indicator of physiological nociceptive. Therefore, the objective of this research is to analyze whether there is a relationship between the intensity of electrical stimulation, subjective perception of voluntary and NFR obtained by EMG of the biceps femoris after electrical stimulation of the same side sural nerve. Participated in the experiment 10 healthy males, aged 20-27 years in the Biomedical Engineering Laboratory of Federal University of Uberlândia UFU. In the right lower limb (dominant) the volunteer was positioned on the track retromalleolar outer electrode of the sural nerve stimulation. In the biceps femoris muscle of the same member, the electrode was fixed surface EMG. The stimulus parameters are determined in the equipment Neuropack S1 MEB-9400 Nihon Kohden, which were as follows: 5 rectangular pulse trains with 0.2 ms and 10 ms interval between pulses. The acquisition of electromyographic signals was controlled by software Myosystem-Br1 version 3.5.6. Using a visual analog scale (VAS), was determined and the pain threshold and tolerance level of the subject of research, which were normalized with 0% and 100% respectively. We analyzed the approximate entropy, the area of the EMG signal, the VAS and the RMS (root mean squared) as a function of the intensity of electrical stimulation applied. The approximate entropy was evaluated by means of electromyographic signal, 100 ms before (PréEn) and 200 ms later (PósEn) of electrical stimulation. The data were stored on .txt and analyzed with MatLab, where a specific interface was developed to process the signals collected. There was a statistical analysis based on Pearson\'s correlation coefficient (r), coefficient of determination (r2) and linear regression. There was a strong positive linear correlation of VAS as a function of stimulus, with r = 0.998307 and r2 = 0.9966. The PréEn showed a weak negative linear correlation, with = -0.67741 and r2 = 0.4589 and PósEn a strong negative linear correlation with respect to the stimulus, with r = -0.93315 and r2 = 0.8708. The area showed strong positive linear correlation in relation to the applied stimulus (r = 0.974094 and r2 = 0.9489), and the RMS 200 ms after stimulation (r = 0.97 and r2 = 0.946). Therefore, it was observed that the variables PósEn, RMS and area of flexion reflex are relevant parameters in the correlation of subjective pain. / A dor é uma sensação desagradável associada a um dano tecidual real ou potencial. A avaliação da dor é muito importante para estabelecer a eficácia de analgésicos e terapias, no entanto, por ser uma experiência complexa e subjetiva torna-se necessário um método que a quantifique objetivamente. Biopotenciais, como os sinais de eletromiografia (EMG) podem auxiliar no estudo da dor. O reflexo de flexão nociceptivo (RFN), que é observado no músculo bíceps femoral com a estimulação elétrica no nervo sural ipsilateral, tem sido utilizado como um indicador nociceptivo fisiológico. Sendo assim, o objetivo desta pesquisa é analisar se há relação entre a intensidade do estímulo elétrico, percepção subjetiva do voluntário e o RFN obtido através da EMG do músculo bíceps femoral após eletroestimulação do nervo sural ipsilateral. Participaram do experimento 10 indivíduos saudáveis do gênero masculino, com faixa etária de 20 a 27 anos no Laboratório de Engenharia Biomédica da Universidade Federal de Uberlândia UFU. No membro inferior direito (dominante) do voluntário, foi posicionado sobre a via retromaleolar externa do nervo sural o eletrodo de eletroestimulação. No músculo bíceps femoral do mesmo membro, foi fixado o eletrodo de EMG de superfície. Os parâmetros do estímulo foram determinados no equipamento Neuropack S1 MEB-9400 Nihon Kohden, os quais foram os seguintes: 5 trens de pulso retangulares com 0,2 ms de duração e intervalo de 10 ms entre os pulsos. A aquisição dos sinais eletromiográficos foi controlada pelo software Myosystem-Br1 versão 3.5.6. Utilizando-se a Escala Visual Analógica (EVA), foi determinado o limiar de dor e o nível de tolerância do sujeito de pesquisa, os quais foram normalizados com 0% e 100% respectivamente. Foi analisada a entropia aproximada, a área do sinal eletromiográfico, a EVA e o RMS (root mean squared) em função da intensidade do estímulo elétrico aplicado. A entropia aproximada foi avaliada, através do sinal eletromiográfico, 100 ms antes (PréEn) e 200 ms depois (PósEn) do estímulo elétrico. Os dados foram armazenados em .txt e analisados com o software MatLab, onde foi desenvolvida uma interface específica para processar os sinais coletados. Fez-se a análise estatística com base no Coeficiente de Correlação de Pearson (r), Coeficiente de Determinação (r2) e regressão linear. Houve uma correlação linear forte positiva da EVA em função do estímulo, com r = 0,998307 e r2 = 0,9966. A PréEn demonstrou uma correlação linear fraca negativa, sendo r = -0,67741 e r2 = 0,4589 e a PósEn uma correlação linear forte negativa em relação ao estímulo, com r = -0,93315 e r2 = 0,8708. A área apresentou correlação linear forte positiva em relação ao estímulo aplicado (r = 0,974094 e r2 = 0,9489), bem como o RMS 200 ms após o estímulo (r = 0,97 e r2 = 0,946). Portanto, foi possível observar que as variáveis PósEn, RMS e área do reflexo de flexão são parâmetros relevantes na correlação subjetiva da dor. / Doutor em Ciências

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Contexte et objectif : La pleine conscience et l’hypnose sont deux moyens non pharmacologiques de réduire la douleur. La combinaison de ces deux outils a montré des effets synergiques dans certains contextes cliniques, mais n’a pas encore était étudié dans un contexte de modulation de la douleur. L’objectif de ce travail est d'évaluer les réponses du système nerveux autonome (SNA) par ses manifestations physiologiques - variabilité du rythme cardiaque (VRC) et activité électrodermale (AED) ainsi que les réponses réflexes de retrait nociceptif (RIII), à des stimuli électriques nociceptifs en contexte hypnotique de pleine conscience et de dissociation chez des participants sains. Méthode : 48 individus (13 pilotes et 35 participants) ont été conviés à 2 sessions pour évaluer les prédispositions individuelles à l’hypnose (échelle SHSS) et la pleine conscience (questionnaire FFMQ) (session 1) puis pour l'expérience principale évaluant la modulation de la douleur (session 2). L'expérience principale comprenait 4 conditions expérimentales administrées chez tous les participants (devis intrasujet) : (1) contrôle passif de repos (baseline) (2) contrôle hypnotique avec suggestions neutres, (3) hypnose avec suggestions de dissociation, et (4) hypnose avec suggestions de pleine conscience. Chaque condition est subdivisée en 2 blocs pendant lesquels les suggestions verbales sont données (bloc 1), puis pendant l’administration des stimuli électriques nociceptifs (bloc 2)). Les données physiologiques ont été enregistrées en continu et la douleur perçue a été rapportée après chaque stimulus nociceptif. Des modèles linéaires mixtes multiniveaux et des tests de corrélation permettent respectivement d’évaluer les contrastes entre les conditions et évaluer les relations entre la modulation des réponses à la douleur et les prédispositions individuelles à l’hypnose et à la pleine conscience. Résultats : Nos résultats confirment que plusieurs indices de la VRC et de l’AED permettent de mesurer les réponses autonomes à la douleur (MeanNN, LFn, HFn, SCL, SCR : p<.001, SD1/SD2 : p<.005, RMSSS p<.05). Toutes les conditions hypnotiques ont permis de diminuer les scores de douleur (p<.05) et ont montré des différences de VRC (RMSSD, SD1 SD2 : p<.05) comparativement à la condition baseline. La condition de dissociation a permis la plus grande diminution des scores de douleurs ainsi que des réponses réflexes diminuées (p<.001). Les participants avec un score SHSS plus élevé ont montré une plus grande diminution du RIII durant les conditions hypnotiques (neutre : p<.05, dissociation et pleine conscience : p<.005). Discussion : Nos résultats fournissent des preuves supplémentaires en faveur de la capacité des suggestions hypnotiques à moduler l’activité physiologique. Les suggestions hypnotiques de dissociation et de pleine conscience ont montré un effet antinociceptif mesuré par les scores de douleur, par une réactivité autonome modifiée et par des réponses réflexes diminuées comparativement à la condition baseline. Toutefois, les réponses autonomes à la douleur et le RIII n’ont pas été significativement différentes entre les conditions hypnotiques. Les personnes hautement susceptibles à l’hypnose pourraient bénéficier d’un effet antinociceptif plus important lors d’interventions hypnoanalgésiques. / Background and objectives: Mindfulness and hypnosis are two non-pharmacological means of reducing pain. The combination of these tools has shown synergistic effects in certain clinical contexts but has not yet been studied in the context of pain modulation. The aim of the present study was to evaluate autonomic nervous system (ANS) responses through physiological manifestations - heart rate variability (HRV) and electrodermal activity (EDA) - as well as nociceptive withdrawal reflex responses (RIII), to nociceptive electrical stimuli in a hypnotic context of mindfulness and dissociation in healthy participants. Method: 48 individuals (13 pilots and 35 participants) were invited to 2 sessions to assess individual predispositions to hypnosis (SHSS scale) and mindfulness (FFMQ questionnaire) (session 1) and then for the main experiment assessing pain modulation (session 2). The main experiment comprised 4 experimental conditions administered to all participants (within-subjects design): (1) passive resting control (baseline) (2) hypnotic control with neutral suggestions, (3) hypnosis with dissociation suggestions, and (4) hypnosis with mindfulness suggestions. Each condition was subdivided into 2 blocks during which verbal suggestions were given (block 1), then during the administration of nociceptive electrical stimuli (block 2)). Physiological data were recorded continuously, and perceived pain was reported after each nociceptive stimulus. Multilevel linear mixed models and correlation tests were respectively used to assess contrasts between conditions, and to evaluate relationships between modulation of pain responses and individual predispositions to hypnosis and mindfulness. Results: Our results confirm that several HRV and EDA indices measure autonomic responses to pain (MeanNN, LFn, HFn, SCL, SCR: p<.001, SD1/SD2: p<.005, RMSSS p<.05). All hypnotic conditions decreased pain scores (p<.05) and showed differences in HRV (RMSSD, SD1 SD2: p<.05) compared with the baseline condition. The dissociation condition resulted in the greatest decrease in pain scores as well as diminished reflex responses (p<.001). Participants with a higher SHSS score showed a greater decrease in RIII during the hypnotic conditions (neutral: p<.05, dissociation and mindfulness: p<.005). Discussion: Our results provide further evidence in favor of the ability of hypnotic suggestions to modulate physiological activity. Hypnotic dissociation and mindfulness suggestions showed an antinociceptive effect measured by pain scores, altered autonomic reactivity, and decreased reflex responses compared to the baseline condition. However, autonomic pain responses and RIII were not significantly different between hypnotic conditions. People who are highly susceptible to hypnosis may benefit from a greater antinociceptive effect during hypnoanalgesic interventions.