Background Virtual reality hypnosis (VRH) is a promising tool to reduce pain. However, the benefits of VRH on pain perception and on the physiological expression of pain require further investigation. Objective In this study, we characterized the effects of VRH on the heat pain threshold among adult healthy volunteers while monitoring several physiological and autonomic functions. Methods Sixty healthy volunteers were prospectively included to receive nociceptive stimulations. The first set of thermal stimuli consisted of 20 stimulations at 60°C (duration 500 milliseconds) to trigger contact heat evoked potentials (CHEPs). The second set of thermal stimuli consisted of ramps (1°C/second) to determine the heat pain threshold of the participants. Electrocardiogram, skin conductance responses, respiration rate, as well as the analgesia nociception index were also recorded throughout the experiment. Results Data from 58 participants were analyzed. There was a small but significant increase in pain threshold in VRH (50.19°C, SD 1.98°C) compared to that in the control condition (mean 49.45°C, SD 1.87; P<.001, Wilcoxon matched-pairs signed-rank test; Cohen d=0.38). No significant effect of VRH on CHEPs and heart rate variability parameters was observed (all P>0.5; n=22 and n=52, respectively). During VRH, participants exhibited a clear reduction in their autonomic sympathetic tone, as shown by the lower number of nonspecific skin conductance peak responses (P<.001, two-way analysis of variance; n=39) and by an increase in the analgesia nociception index (P<.001, paired t-test; n=40). Conclusions The results obtained in this study support the idea that VRH administration is effective at increasing heat pain thresholds and impacts autonomic functions among healthy volunteers. As a nonpharmacological intervention, VRH has beneficial action on acute experimental heat pain. This beneficial action will need to be evaluated for the treatment of other types of pain, including chronic pain.

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BACKGROUND Virtual reality hypnosis (VRH) is a promising tool to reduce pain. However, VRH benefits on pain perception and on the physiological expression of pain still require further investigation. OBJECTIVE In this study, we characterized the effects of VRH on heat pain threshold in adult healthy volunteers and simultaneously monitored several physiological and autonomic functions. METHODS 60 healthy volunteers were prospectively included to receive nociceptive stimulations. The first series of thermal stimuli consisted of 20 stimulations at 60°C (duration: 500 ms) to trigger contact heat evoked potentials (CHEPs). The second series of thermal stimuli consisted of temperature ramps (1°C/sec) to determine the thermal pain thresholds of the participants. Electrocardiogram, electrodermal conduction, respiration rate as well as the analgesia nociception index were also recorded throughout the experiment. RESULTS Data from 58 participants were analysed. There was a significant increase in pain threshold in VRH compared to NoVRH (p<0.001, Wilcoxon matched-pairs signed ranks). No significant effect of VRH on CHEPs and heart rate parameters was observed. Compared to control, VRH subjects display a clear reduction in their autonomic sympathetic tone as seen by the low number of non-specific skin conductance peak responses (p = 0.0007, 2-way ANOVA) and the analgesia nociception index increase (p = 0.0005; paired t-test). CONCLUSIONS The results obtained in this study support the idea that VRH administration to healthy volunteers is effective at increasing heat pain thresholds and impacts autonomic functions. As a non-pharmacological intervention, VRH has beneficial action on acute experimental heat pain. This beneficial action will now need to be evaluated for the treatment of other types of pain including chronic pain.

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