Improving ice cooling exposure (ICE) to assess in vivo circulatory homeostatic reflexes

Skin microcirculation has been proposed as a model of generalized microvascular function, representing a practical as easily accessible model to apply in multiple in vivo studies. In vascular medicine, the post-occlusive reactive hyperemia (POHR) is a popular procedure although somewhat uncomfortable due to the cuff pressure. Alternative procedures such as using skin cooling as a challenger to promote reactive hyperemia have not been sufficiently explored. We hypothesized that ice cooling exposure (ICE) might be a valuable and better-tolerated methodology for studying skin microcirculatory adaptive responses. Thus, our study compares perfusion changes assessed by laser Doppler flowmetry (LDF) during POHR and ICE. The aim is to define optimized protocols for its application. Eleven healthy women, 29.3±7.3 years old, were selected. After stabilization, participants were sequentially submitted to these two challengers, applied in one randomly selected limb. POHR was induced with a pressure cuff (2 minute occlusion), while ICE involved the contact of the palmar side of one hand with a frozen surface covered by a sheet paper for 10 minutes. Blood perfusion and skin temperature were continuously measured by LDF in both hands, before, during, and after the challenge in both protocols. PORH greatly reduced the LDF signal amplitude during cuff insufflation (200 mmHg) followed by significant hyperemia after cuff deflation. ICE evoked significant decreases in skin temperature and perfusion, followed by reperfusion after ceasing ICE. Similar responses were observed in the contralateral limb. A significant correlation between LDF and temperature signals across phases and limbs was observed [POHR: Spearman’s correlation coefficient ( rs) = 0.633 ( p < 0.001); cold challenge: rs = 0.820 (p < 0.001)]. The duration of cold exposure necessary for a significant difference in LDF and temperature measures between the baseline and the challenge phases across limbs was 3 minutes (Wilcoxon test, p<0.01). In conclusion, our study indicates that ICE might be an effective method for eliciting cardiocirculatory adaptive reflexes suitable for application in vascular medicine and a better tolerated alternative to POHR. Furthermore, in vascular pathologies such as Raynaud’s phenomenon, our ICE protocol is less invasive and may be more informative than the cold immersion test currently used as the gold standard for thermography studies. FCT—Foundation for Science and Technology, I.P. (Portugal) [UIDB/04567/2020] and [UIDP/04567/2020] programs. All imaging instrumentation was provided by ALIES-COFAC. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.