The effect of foot temperature on laser speckle contrast imaging (LSCI) and transcutaneous oxygen pressure (TcPO2) measurements.

BACKGROUND/AIM: Assessment of foot microcirculation is increasingly implemented into clinical practice to assess vascular status and wound-healing potential in patients with vascular disease when conventional assessment techniques provide limited or unreliable information. Transcutaneous oxygen pressure (TcPO2) and laser speckle contrast imaging (LSCI) are techniques used to assess microcirculation in the foot. However, foot temperature is currently not considered during TcPO2 and LSCI measurements, despite substantial variation between patients and across measurements. Determining its influence is therefore crucial to ensure measurement reliability and reproducibility in clinical practice. This study aimed to determine the influence of foot temperature on TcPO2 and LSCI measurements. METHOD: Physiological foot temperatures ranging from 25 °C to 35 °C were simulated in 30 healthy participants using cold and warm water immersion. Subsequently, plantar LSCI perfusion and skin temperature measurements were obtained, together with dorsal TcPO2 and skin temperature measurements around the electrodes. RESULTS: TcPO2 and LSCI mean perfusion values differed significantly between foot temperatures of 25 °C and 35 °C, with higher temperatures yielding higher values for both techniques. Despite these clear differences, interindividual variability was seen and no consistent relation was observed between temperature changes and corresponding TcPO2 values. LSCI perfusion followed an exponential relation with foot temperature, but prediction intervals were wide. CONCLUSION: Foot temperature following water immersion significantly influences TcPO2 and LSCI measurements, although temperature responses vary between individuals. For TcPO2, this effect remained present despite local electrode heating, indicating that surrounding foot temperature continues to affect measurements. Clinicians should therefore consider foot temperature when interpreting TcPO2 and LSCI measurements.