Harrison J L, Davis K D
Institute of Medical Sciences, University of Toronto, Toronto, Canada.
Pain. 1999 Nov;83(2):123-35. doi: 10.1016/s0304-3959(99)00099-8.
The psychophysical responses to noxious cold stimulation of the skin in normal human subjects are not well understood. Continuous pain ratings with the visual analogue scale is an important method to assess these responses. In this study, we addressed several important issues about the parameters with which stimuli are delivered: the type of skin stimulated, the rate with which the stimulus temperature decreases, and the dimension of the pain rated by subjects. Cold stimuli were delivered to the thenar eminence (glabrous skin) and the dorso-lateral hand (hairy skin) via a 4 cm(2) Peltier-type stimulator. Cold and pain thresholds were determined by the method of limits (MOL). A computerized visual analogue scale (VAS) was used to obtain continuous ratings of pain intensity and affect. The McGill Pain Questionnaire (MPQ) was used to assess the quality of cold-evoked pain. Supra-threshold stimuli (34 degrees C base) were delivered at 0.5, 1 or 2 degrees C/s to 2 degrees C, held for 20s and returned to baseline at 9 degrees C/s. These studies revealed: (1) Cold thresholds, measured with MOL, were lower (i.e. occurred at higher absolute temperatures) for the hairy skin of the dorso-lateral hand compared to the glabrous skin of the thenar eminence. (2) A similar pattern was evident for cold induced pain thresholds with MOL at 1.5 degrees C/s and with intensity and affect VAS scales at 0.5 and 1 degrees C/s. (3) Exponents for supra-threshold ratings fit to power functions were larger for the glabrous skin site than the hairy skin site regardless of cooling rate or dimension of pain measured. (4) All pain indices were higher for slower cooling rates. (5) No significant differences were found in the pain indices for pain ratings of intensity and affect. (6) A substantial proportion of subjects chose words representing paradoxical heat with the MPQ. (7) Painful paradoxical heat sensations occurred most often during cooling, while innocuous warm sensations mainly occurred during the rewarming phase.
正常人类受试者对皮肤有害冷刺激的心理物理反应尚未得到充分理解。使用视觉模拟量表进行连续疼痛评分是评估这些反应的重要方法。在本研究中，我们探讨了与刺激传递参数相关的几个重要问题：受刺激的皮肤类型、刺激温度下降的速率以及受试者评定的疼痛维度。通过一个4平方厘米的珀尔帖式刺激器将冷刺激施加于鱼际隆起（无毛皮肤）和手的背外侧（有毛皮肤）。冷觉阈值和痛觉阈值通过极限法（MOL）测定。使用计算机化视觉模拟量表（VAS）来获取疼痛强度和情感的连续评分。使用麦吉尔疼痛问卷（MPQ）来评估冷诱发疼痛的性质。阈上刺激（基础温度34摄氏度）以0.5、1或2摄氏度/秒的速率降至2摄氏度，保持20秒，然后以9摄氏度/秒的速率恢复到基线。这些研究揭示：（1）与鱼际隆起的无毛皮肤相比，手的背外侧有毛皮肤用MOL测量的冷觉阈值更低（即在更高的绝对温度下出现）。（2）在1.5摄氏度/秒时用MOL以及在0.5和1摄氏度/秒时用强度和情感VAS量表测量的冷诱发痛觉阈值也呈现出类似模式。（3）无论冷却速率或所测量的疼痛维度如何，阈上评分拟合幂函数的指数在无毛皮肤部位比有毛皮肤部位更大。（4）所有疼痛指标在冷却速率较慢时更高。（5）在强度和情感疼痛评分的疼痛指标方面未发现显著差异。（6）相当一部分受试者在MPQ中选择了代表矛盾性热感的词汇。（7）疼痛性矛盾性热感最常出现在冷却过程中，而无害的温暖感主要出现在复温阶段。
