Types of pain stimulators

In order to carry out experiments on volunteers for the study of pain processing, it is necessary to use some sort of pain stimulus. For a pain stimulator to be suitable, it must be both controllable and safe. Possible types of pain stimulator include electrical, mechanical and thermal stimulators, which all have their advantages and disadvantages.

The pain stimulators which we use are thermal stimulators, which cause pain by heating the skin to painful temperatures. These stimulators may be divided into two categories: contact thermal stimulators (thermodes) and radiant heat stimulators (lasers). Lasers have the advantage over contact thermodes that they can produce rapid heating of the skin for short periods of time. In addition, they heat the skin without touching it, hence activating A-delta and C nerve fibres responsible for pain sensation without activating A-beta nerve fibres responsible for the sensation of touch.

We use two types of laser stimulators for pain research: a carbon dioxide (CO2) laser pain stimulator and a thulium (Tm) fibre laser pain simulator. These lasers have been developed in collaboration with the Laser Photonics Research Group in the School of Physics and Astronomy and the Medical Physoics Department at Salford Royal NHS Foundation Trust (SRFT).