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Spatial temperature distribution in human hairy and glabrous skin after infrared CO2 laser radiation.

Frahm KS, Andersen OK, Arendt-Nielsen L, Mørch CD - Biomed Eng Online (2010)

Bottom Line: The laser energy is absorbed by the water content in the most superficial layers of the skin.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.The model simulations of superficial temperature correlated with the measured skin surface temperature (r > 0.90, p < 0.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajers vej 7D-3, DK 9220 Aalborg, Denmark. ksf@hst.aau.dk

ABSTRACT

Background: 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.

Methods: In 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.

Results: The 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.

Conclusions: As 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.

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Related in: MedlinePlus

The figure illustrates how the temperature is dispersed in hairy and glabrous skin following a 0.6 J/cm2 (5 W, 0.12 s) stimulation as a result of finite element modeling. The plots represent the time at stimulus offset (A, D - 0.12 s), 1.5 × stimulus duration (B, E - 0.18 s) 2 × stimulus duration (C, F - 0.24 s). The horizontal grey line represents the epidermal ridge (50 μm in hairy skin and 130 μm in glabrous skin).
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Figure 10: The figure illustrates how the temperature is dispersed in hairy and glabrous skin following a 0.6 J/cm2 (5 W, 0.12 s) stimulation as a result of finite element modeling. The plots represent the time at stimulus offset (A, D - 0.12 s), 1.5 × stimulus duration (B, E - 0.18 s) 2 × stimulus duration (C, F - 0.24 s). The horizontal grey line represents the epidermal ridge (50 μm in hairy skin and 130 μm in glabrous skin).

Mentions: Only the 5 W power setting was used for estimating nociceptors depth, since many 1 W stimulations did not evoke any sensations. Treede et al. [3] reported that only the presence of type II AMHs (Aδ mechano-heat nociceptors) differs between hairy and glabrous skin. Evidently, CMH (C mechano-heat nociceptors) and type I AMH were present in both types of skin suggesting that any difference in activation of these fibers must reflect different localization in the skin and different thermal properties of the two types of skin. The present results indicated that equal stimulation in glabrous skin caused longer reaction times and less intense pain than in hairy skin, which could be caused by the different thermal properties of the skin types or the possible activation of type II AMHs when stimulating hairy skin. Assuming an intradermal initial temperature of 34°C and the threshold for activation of Aδ nociceptors is 46°C [3] this would correspond to a temperature increase of 12°C. The model indicates that an increase of 12°C can only occur at depths shallower than 100 μm. This is also demonstrated in Figure 10, which indicates the spatial subsurface heat distribution. Similar results have been obtained with an analytical modeling technique [14]. Both the current study and previous work [14] suggest that when using CO2 lasers more stimulation energy will be required to activate deeper located nociceptors.


Spatial temperature distribution in human hairy and glabrous skin after infrared CO2 laser radiation.

Frahm KS, Andersen OK, Arendt-Nielsen L, Mørch CD - Biomed Eng Online (2010)

The figure illustrates how the temperature is dispersed in hairy and glabrous skin following a 0.6 J/cm2 (5 W, 0.12 s) stimulation as a result of finite element modeling. The plots represent the time at stimulus offset (A, D - 0.12 s), 1.5 × stimulus duration (B, E - 0.18 s) 2 × stimulus duration (C, F - 0.24 s). The horizontal grey line represents the epidermal ridge (50 μm in hairy skin and 130 μm in glabrous skin).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2991325&req=5

Figure 10: The figure illustrates how the temperature is dispersed in hairy and glabrous skin following a 0.6 J/cm2 (5 W, 0.12 s) stimulation as a result of finite element modeling. The plots represent the time at stimulus offset (A, D - 0.12 s), 1.5 × stimulus duration (B, E - 0.18 s) 2 × stimulus duration (C, F - 0.24 s). The horizontal grey line represents the epidermal ridge (50 μm in hairy skin and 130 μm in glabrous skin).
Mentions: Only the 5 W power setting was used for estimating nociceptors depth, since many 1 W stimulations did not evoke any sensations. Treede et al. [3] reported that only the presence of type II AMHs (Aδ mechano-heat nociceptors) differs between hairy and glabrous skin. Evidently, CMH (C mechano-heat nociceptors) and type I AMH were present in both types of skin suggesting that any difference in activation of these fibers must reflect different localization in the skin and different thermal properties of the two types of skin. The present results indicated that equal stimulation in glabrous skin caused longer reaction times and less intense pain than in hairy skin, which could be caused by the different thermal properties of the skin types or the possible activation of type II AMHs when stimulating hairy skin. Assuming an intradermal initial temperature of 34°C and the threshold for activation of Aδ nociceptors is 46°C [3] this would correspond to a temperature increase of 12°C. The model indicates that an increase of 12°C can only occur at depths shallower than 100 μm. This is also demonstrated in Figure 10, which indicates the spatial subsurface heat distribution. Similar results have been obtained with an analytical modeling technique [14]. Both the current study and previous work [14] suggest that when using CO2 lasers more stimulation energy will be required to activate deeper located nociceptors.

Bottom Line: The laser energy is absorbed by the water content in the most superficial layers of the skin.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.The model simulations of superficial temperature correlated with the measured skin surface temperature (r > 0.90, p < 0.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajers vej 7D-3, DK 9220 Aalborg, Denmark. ksf@hst.aau.dk

ABSTRACT

Background: 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.

Methods: In 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.

Results: The 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.

Conclusions: As 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.

Show MeSH
Related in: MedlinePlus