Drewes A M, Pedersen J, Liu W, Arendt-Nielsen L, Gregersen H
Laboratory for Visceral Pain and Biomechanics, Dept. of Medical Gastroenterology, Aalborg Hospital, Denmark.
Scand J Gastroenterol. 2003 Jan;38(1):27-35.
The relation between mechanical distension of the gut and the sensory response is poorly understood. The current experimental study aimed to examine the sensory response in the human oesophagus during on-line recording of the luminal pressure, cross-sectional area (CSA) and sensory rating using different distension rates before and during relaxation of the smooth muscle.
An impedance planimetric probe for bag distension of the oesophagus was used in 13 healthy subjects aged 43 +/- 15 years. Ramp distensions were done with an electromechanical pump using infusion rates of 10, 25 and 50 ml/min, with and without relaxation of the smooth muscle with butylscopolamine. The sensory intensity was measured using a 0-10 visual analogue scale (VAS), with 5 as the pain threshold. The pump was reversed at 8 on the scale, corresponding to medium pain intensity, and the pressure, volume, tension and CSA were evaluated. Finally, three isovolumetric experiments where the CSA was held constant for 2 min at initial VAS ratings of 3, 5 and 7 were performed.
A total of 104 distension profiles were investigated. The volume at maximal pain intensity (VAS = 8) increased as a function of the distension rate (P < 0.001), whereas the pressure, tension and CSA were not affected. When the smooth muscle was relaxed, there was a 29% fall in pressure at maximal pain intensity (P = 0.004), a 27% fall in tension (P = 0.003), whereas CSA did not change (P = 0.3). When the pressure was recorded as a function of the sensory intensity, there was an exponential increase after the pain threshold was reached, whereas the stimulus-response functions for tension, volume and CSA were nearly linear. In the isovolumetric experiments the ratings during the three sensory intensities were the same in the individual subjects, but the between-individual pain response was variable, probably reflecting individual differences in adaptation/central integration.
The study allowed us to assess the strain-rate dependency of both perception and biomechanical properties in the oesophagus. It was demonstrated that the pain response was related to the CSA (and hence strain), independently of the contractile state of the muscle and biomechanical behaviour of the tissue. The findings support the fact that the pain-sensitive mechanoreceptors in the human oesophagus depend on circumferential wall stretch rather than on pressure, tension and volume. The model should be used in future studies to investigate whether changes in strain are responsible for the oesophageal sensation in health and disease.
肠道机械扩张与感觉反应之间的关系尚不清楚。当前的实验研究旨在通过在线记录管腔内压力、横截面积（CSA）以及在平滑肌舒张前后使用不同扩张速率时的感觉评分，来检测人体食管的感觉反应。
对13名年龄为43±15岁的健康受试者使用用于食管气囊扩张的阻抗平面测量探头。使用电动机械泵以10、25和50毫升/分钟的输注速率进行斜坡扩张，在有和没有用丁溴东莨菪碱使平滑肌舒张的情况下进行。使用0至10的视觉模拟量表（VAS）测量感觉强度，以5作为疼痛阈值。当量表达到8时反转泵，对应中等疼痛强度，并评估压力、体积、张力和CSA。最后，进行了三个等容实验，其中CSA在初始VAS评分为3、5和7时保持恒定2分钟。
共研究了104个扩张曲线。最大疼痛强度（VAS = 8）时的体积随扩张速率增加（P < 0.001），而压力、张力和CSA不受影响。当平滑肌舒张时，最大疼痛强度时压力下降29%（P = 0.004），张力下降27%（P = 0.003），而CSA没有变化（P = 0.3）。当将压力作为感觉强度的函数记录时，达到疼痛阈值后呈指数增加，而张力、体积和CSA的刺激 - 反应函数几乎是线性的。在等容实验中，个体受试者在三种感觉强度下的评分相同，但个体间的疼痛反应是可变的，这可能反映了适应/中枢整合方面的个体差异。
该研究使我们能够评估食管中感知和生物力学特性的应变率依赖性。结果表明，疼痛反应与CSA（因此与应变）相关，与肌肉的收缩状态和组织的生物力学行为无关。这些发现支持了这样一个事实，即人类食管中对疼痛敏感的机械感受器取决于周向壁伸展而非压力、张力和体积。该模型应在未来的研究中用于调查应变变化是否与健康和疾病状态下的食管感觉有关。
