Validation of a transient pain monitor in healthy volunteers

Background and Objectives: Transient pain in humans is usually quantified using visual analog or numeric rating scales, but no assessment method has yet been validated in real time during such stimulation. Methods: To validate a transient pain monitor, healthy volunteers submitted to stimulations generated by a CO2 laser at graded levels of stimulation were trained to close the dominant hand around a handgrip dynamometer as strongly as they felt the pain, and the signal was computerized. The parameters recorded for each response were the peak intensity, the area under the curve, and pain expressed on a visual analog scale as a control. The volunteers underwent a second session 1 week later to assess reproducibility. Results: The 3 parameters studied had a similar capacity to report the intensity of stimulation. The peak intensity showed many similarities with the visual analog scale, although a downward drift of the values throughout the session was observed. The area under the curve displayed a greater interindividual variability than other parameters, but it was better to assess low-intensity stimulation; a better fit for crossover designs was also suggested with the area under the curve. Conclusions: This study validates in human volunteers under a laser stimulation of skin the metrological properties of an electronic handgrip device to assess the intensity of transient punctuate pain (compared with visual analog scale). The transient pain monitor validated here should now be tested in the clinical context.