Conditioned pain modulation assessment using contact heat as conditioning stimulus and two different test stimuli

Abstract

Introduction. The objective of the study was to determine the potentials and reliability of conditioned pain modulation effect in healthy population by application of a conditioning contact heat stimulus, and heat and pressure applied to the low back region as a test stimulus. Material and Methods. The study included 33 healthy subjects (average age 25.73 ? 5.35 years). Pressure and heat pain thresholds were examined on the paravertebral musculature of the lower back as test stimuli. Contact heat was used on the contralateral forearm as a conditioning stimulus. Conditioned pain modulation was calculated as the difference between pain thresholds after and before conditioning stimulus application. To assess the reliability, identical testing was performed 14 ? 2 days later. Results. The pressure and heat pain thresholds, after the conditioning stimulus, were significantly higher compared to pain thresholds obtained before the conditioning stimulus (101,63 N/cm2 ? 45,21N/cm2 vs 82,15 N/cm2 ? 36,15 N/cm2, t = -7,528, p < 0,001 and 47,08?C ? 2,19o C vs 45,00 ? 3,05?C, t = -6,644, p < 0,001, respectively). The reli?ability of the same protocol, measured 14 ? 2 days after the previous testing, showed good reliability of the pressure pain threshold (intraclass correlation coefficient = 0,636, 95% confidence interval 0,240 - 0,825), and fair of the heat pain threshold (intraclass cor?relation coefficient = 0,435, 95% confidence interval - 0,070 - 0,713). Conclusion. Conditioned pain modulation was successfully induced by contact heat applied via a thermode, a conditioning stimulus. The reliability of this method of testing proved to be fair when it comes to the heat pain threshold and good when it comes to the pressure pain threshold.