Tackling variability of Laser-Doppler flowmetry in vivo measurements in glabrous skin

Introduction: Laser Doppler Flowmetry (LDF) is likely the most popular non-invasive technology used to assess in vivo skin perfusion. Although it enables fast as reproducible measurements, recorded signals vary substantially due to the non-uniform, pulsatile nature of the signal itself, along with differing instrument specifications and probe architectures. Such variability serves as a major obstacle to define measurable and comparable outcomes. In this study we compared perfusion measurements obtained in human with two (single and multifibre) LDF probes and explored normalization strategies to reduce variability of these signals. Methods: Fourteen LDF independent recordings were obtained from healthy volunteers, both sexes (40.7±15.2 years old) using probes VP1T, a single delivery/single collecting fiber, and VP1T/7, a single delivery/eight collecting fibers, from Moor Instruments. These two probes’ designs provide different capacities to assess microvascular blood dynamics in vivo. Probes were placed on the index finger (VP1T) and middle finger (VP1T/7) in the palmar aspect of both hands. The experimental protocol involved a 10-minute recording period for baseline, a 2-minute period during an arterial occlusion manoeuvre (200 mmHg) in one (ipsilateral) arm, and a 10-minute post-occlusion recording during recovery. Values were collected as means ± standard deviation and further normalised relative to baseline [(value – mean baseline)/mean baseline]. All procedures observed the ethical standards for clinical studies in human. Statistical analysis was performed using Student’s t-test (p < 0.05). Results: The VP1T/7 consistently showed higher perfusion values throughout the protocol compared to VP1T probe. Baseline perfusion recorded with the VP1T probe was significantly lower (234 ± 139 PU) than with the VP1T/7 (305 ± 196 PU; p = 0.014). Both probes detected significant perfusion differences between baseline and occlusion mean values for both the ipsilateral and contralateral arm. When comparing baseline and early recovery, significant differences were found only for the ipsilateral arm values recorded with VP1T. Normalization reduced inter-probe variability, allowing direct comparison of dynamic response profiles. After normalization, significant differences were observed between baseline and early reperfusion, with both probes in both arms. Conclusion: Although the 8-fiber VP1T/7 probe consistently captured higher perfusion values, results between probes were only comparable after normalisation. Hence, normalization seems to be crucial for accurate and meaningful comparison of results to ensure that the data more accurately reflects variations in perfusion rather than other discrepancies affecting the signal. This abstract was presented at the American Physiology Summit 2026 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.