Cutaneous microvascular functional assessment during exercise: a novel approach using laser speckle contrast imaging

Cardiovascular diseases are often revealed during exercise and are associated with cutaneous blood flow (CBF) dysfunction. Studies of CBF during exercise are consequently of interest. Laser speckle contrast imaging (LSCI) allows for non-contact and real-time recording of CBF at rest. We tested whether LSCI could allow the study of CBF during a cycling exercise using a specific signal treatment procedure that removes movement-induced artefacts from the LSCI raw signal. We recorded the baseline CBF and peak post-occlusive reactive hyperaemia (PORH) from the cutaneous forearm using LSCI and the mean blood pressure before and during cycling (80 W at 70 rpm) in nine healthy subjects. We determined the cross-correlation coefficient r between LSCI traces obtained before and during cycling and before and after a specifically designed signal processing technique. The results are presented as the median (25th-75th centile) and expressed as the cutaneous vascular conductance (laser speckle perfusion units (LSPU) per millimetre of mercury). Cross-correlation r increased from 0.226 +/- 0.140 before to 0.683 +/- 0.170 after post-processing. After signal processing, the peak PORH during exercise was reduced [0.38 (0.30-0.52) LSPU/mmHg] compared with the peak PORH during the non-exercise phase [0.69 (0.63-0.74) LSPU/mmHg, p < 0.01], whereas no difference was found between the baseline values. With adequate signal processing, LSCI appears valuable for investigating CBF during exercise. During constant-load lower limb cycling exercise, the upper limb peak PORH is reduced compared with the peak PORH during non-exercise. The underlying mechanisms warrant further investigations in both healthy (trained) subjects and diseased (e.g., coronary heart disease) patients