A model for the temperature distribution in skin noxiously stimulated by a brief pulse of CO2 laser radiation

Raziel Haimi-Cohen, Arnon Cohen, Amiram Carmon

Research output: Contribution to journalArticlepeer-review

49 Scopus citations


The application of localized noxious heat stimuli to the skin, generated by brief infrared radiation pulses emitted by a CO2 laser, is a relatively new experimental technique for the thermal induction of pain in humans and in experimental animals. This study proposes a model for the spatial (3-dimensional) and temporal distribution of the skin temperature during and following a radiation pulse. The heat equation is written and solved, using thermal and optical constants of human skin reported in the literature. The solution is approximated, with a very small error, by a closed form expression, having a simple physical interpretation. This model is applied to analyze a typical set-up currently in use in our laboratory. The results show a significant difference between the temperature of the surface of the skin and that of the border between the epidermis and the dermis, which is the location of the most superficial receptive nerve ends. It is shown that, for the set-up examined, these nerve ends reach a temperature of 45°C, known to be the human pain threshold, 30-40 ms after pulse onset. Moreover, it is also shown that they may remain above threshold temperature for up to a few hundreds of milliseconds (considerably outlasting pulse cessation). In addition, it is shown that the area in which nerve ends reach this threshold is a circle with a very small radius (1-2.5 mm). The implications of the results on the double sensation experienced by humans, and on the exteremly powerful EEG correlates, are discussed.

Original languageEnglish
Pages (from-to)127-137
Number of pages11
JournalJournal of Neuroscience Methods
Issue number2
StatePublished - 1 Jan 1983


  • CO laser
  • evoked potentials
  • first pain
  • noxious heat
  • second pain
  • skin temperature

ASJC Scopus subject areas

  • General Neuroscience


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