Noncontact monitoring of the peripheral microcirculation using laser speckle contrast imaging to evaluate the skin perfusion pressure

The skin perfusion pressure (SPP) is traditionally measured with laser Doppler flowmetry (LDF), but this technique is limited by its single-point fiber optic probe, the need to contact the skin, and susceptibility to various factors, resulting in poor data consistency. Therefore, we developed a noncontact system for measuring the SPP over a large area based on laser speckle contrast imaging (LSCI). When it was paired with a pressure cuff device, the system accurately recorded blood flow changes during various pressure interventions, and the reperfusion pressure point could be calibrated to overcome traditional measurement limitations. Cross-comparison experiments revealed that the measurements obtained with the LSCI and LDF systems were highly correlated (r > 0.7), confirming the reliability of LSCI in assessing microcirculatory function. Since supine measurements are not always suitable in clinical environments, such as in space-constrained clinics or when the patient cannot lie flat, we compared SPP measurements obtained from individuals in sitting versus supine positions, revealing minimal differences (Cohen's d = 0.1, p > 0.05), which demonstrates the system's stability over different patient postures. Under cold water stimulation, which induces microvascular contraction, simulating poor circulation, the measured SPP was significantly lower than that measured under normal conditions (Cohen's d = 2.6, p < 0.05), verifying the system's potential applicability under different pathological conditions. According to our results, the LSCI system not only obtains SPP measurements that are correlated with the LDF-measured SPP but also overcomes the limitations of the latter system, providing noncontact, instant, and large-scale microcirculation monitoring. This study offers a reliable microcirculatory assessment tool based on LSCI technology, and the results support the future application of this tool in the early diagnosis and monitoring of diabetic foot neuropathy and peripheral arterial disease.