The hypoalgesic effect of 3-D video glasses on cold pressor pain: reproducibility and importance of information.

The first aim of the study was to evaluate whether it was possible to manipulate the distraction effect induced by 3-D video glasses on the perceived pain and unpleasantness of the subjects by giving them different information about the expected effect. Second, the study aimed to determine the reproducibility of the effect. Forty-five students enrolled, 39 students participated in the study (24 women and 15 men, median age 23 years, range 19-28 years) because 6 did not show up for the first trial, and 37 completed the study because 2 subjects did not show up for the second trial. The subjects were randomized into 3 groups, balanced with respect to age and sex, that received different information about the effect of 3-D video on pain and unpleasantness: the first group received positive information, the second group received neutral information, and the third group received negative information. Once assigned to a group, there were no crossovers between the groups. A cold pressor stimulus was used to induce experimental pain, and the volunteers rated the intensity of pain and unpleasantness on 100-mm visual analogue scales. A new generation of video glasses were used in the study. Each volunteer was exposed to the cold pressor test in 2 randomized trials (video and control) after the information was given, and the 2 trials were repeated in a second session after 4 weeks. There was no significant difference in the effect of video glasses on perceived pain (P = .74) nor on the perceived unpleasantness (P = .84) among the 3 information groups. The data were therefore pooled. The results of the pooled data showed a significant effect of 3-D video on perceived pain (P = .03) but not on unpleasantness (P = .18). After 4 weeks, the study was repeated, and there were no significant changes in the effect of video glasses. The median visual analogue scale scores were reduced in both the video and the control trials compared with the first session.