Abstract
BackgroundCO2 lasers have been used for several decades as an experimental non-touching pain stimulator. The laser energy is absorbed by the water content in the most superficial layers of the skin. The deeper located nociceptors are activated by passive conduction of heat from superficial to deeper skin layers.MethodsIn the current study, a 2D axial finite element model was developed and validated to describe the spatial temperature distribution in the skin after infrared CO2 laser stimulation. The geometry of the model was based on high resolution ultrasound scans. The simulations were compared to the subjective pain intensity ratings from 16 subjects and to the surface skin temperature distributions measured by an infrared camera.ResultsThe stimulations were sensed significantly slower and less intense in glabrous skin than they were in hairy skin (MANOVA, p < 0.001). The model simulations of superficial temperature correlated with the measured skin surface temperature (r > 0.90, p < 0.001). Of the 16 subjects tested; eight subjects reported pricking pain in the hairy skin following a stimulus of 0.6 J/cm2 (5 W, 0.12 s, d1/e2 = 11.4 mm) only two reported pain to glabrous skin stimulation using the same stimulus intensity. The temperature at the epidermal-dermal junction (depth 50 μm in hairy and depth 133 μm in glabrous skin) was estimated to 46°C for hairy skin stimulation and 39°C for glabrous skin stimulation.ConclusionsAs compared to previous one dimensional heat distribution models, the current two dimensional model provides new possibilities for detailed studies regarding CO2 laser stimulation intensity, temperature levels and nociceptor activation.
Highlights
CO2 lasers have been used for several decades as an experimental non-touching pain stimulator
The grand averages for all 4 sites in all 16 subjects for the epidermal thickness were in the glabrous skin found to be 0.101 ± 0.04 mm for site 1 and 0.164 ± 0.07 mm for site 2
Physiological significance The present results indicate that the perception latencies in glabrous skin was significantly slower than in hairy skin
Summary
CO2 lasers have been used for several decades as an experimental non-touching pain stimulator. The laser energy is absorbed by the water content in the most superficial layers of the skin. The deeper located nociceptors are activated by passive conduction of heat from superficial to deeper skin layers. Infrared CO2 lasers (10.6 μm) have a very short penetration depth (20 μm) as the energy has to be absorbed by the water content in the stratum corneum and other layers of the epidermis [2,5]. Since approximately 90% of the infrared CO2 laser energy is absorbed in the very superficial stratum corneum and epidermis it has to be passively conducted deeper into the skin to activate the nociceptors. Part of the delay in the transduction process leading to activation of the nociceptors must be due to passive conductance of the thermal energy through the superficial skin layers
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
