Evaluation of temperature-dependent fluctuations in skin microcirculation flow using a light-emitting diode based photoacoustic imaging device

Purpose: Skin microvessels maintain temperature homeostasis by contracting and dilating upon exposure to changes in temperature. Under general anesthesia, surgical invasiveness, including incisions and coagulation, and the effects of anesthetics may cause variations in the threshold temperature, leading to the constriction and dilation of cutaneous blood vessels. Therefore, studies on skin microvascular circulation are necessary to develop appropriate interventions for complications during surgery. Methods: We visualized and quantified skin microcirculatory fluctuations associated with temperature variations using a light-emitting diode photoacoustic imaging (LED-PAI) device. The hands of ten healthy volunteers were stressed with four different water temperatures [25℃ (Control), 15℃ (Cold1), 40℃ (Warm), and 15℃ (Cold2)]. The photoacoustic images of the fingers were taken under each condition, and the microvascular flow owing to temperature stress was quantified as the area of photoacoustic signal (S) in each image. The S values were compared with the variations in blood flow (Q) measured by laser Doppler flowmetry (LDF). Results: The correlation between Q and S according to the 40 measurements was r = 0.45 (p＜0.01). In addition, the values of S under each stress condition were as follows: S control = 10,826 ± 3364 pixels, S cold1 = 8825 ± 2484 pixels, S warm = 13,369 ± 3001 pixels, and S cold2 = 8838 ± 1892 pixels; the differences were significant. The LDF blood flow (Q) showed similar changes among conditions. Conclusion: These findings suggest that the LED-PAI device could be an option for evaluating microcirculation in association with changes in temperature.