Distance between laser head and skin does not influence skin blood flow values recorded by laser speckle imaging.

BACKGROUND

Laser Speckle contrast imaging (LSCI) allows non-contact, real-time recording of cutaneous blood flow (CBF). Different distances from laser-head to skin (distances(L-S)) can be chosen by the operator to perform these recordings. We aimed to evaluate the impact of different Distances(L-S) on the analysis of rest blood flow and post-occlusive reactive hyperemia (PORH).

METHODS

Four distances(L-S) (10, 15, 20, and 30 cm) were evaluated in a random order in 11 healthy subjects. We analyzed the concordance between each recording at each distance(L-S). We compared CBF results (absolute values and cutaneous vascular conductance (CBF divided by mean arterial pressure)) obtained for each distance(L-S). The intra-subject coefficients of variation due to distances(L-S) (intra-CV, in%) were also studied.

RESULTS

The mean "r" (standard deviation) cross-correlation coefficient was 0.99 (0.00) between each CBF trace issued from different distance(L-S). Both kinds of CBF results, at rest and for PORH peak, show non-significant differences when the distance(L-S) is modified. The intra-CV varies from 5.9% to 8.6% at rest and from 5.6% to 9.1% for the PORH peak.

CONCLUSION

Distance(L-S) neither influences SBFR at rest, nor at peak post-occlusive hyperemia in the 10-30 cm interval using LSCI.