title: Distance between laser head and skin does not influence skin blood flow values recorded by laser speckle imaging.
abstract: 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.
  
  
  CONCLUSIONS
  Distance(L-S) neither influences SBFR at rest, nor at peak post-occlusive hyperemia in the 10-30 cm interval using LSCI.
authors.affiliation: Laboratory of Vascular Investigations, University Hospital of Angers, France. maheguillaume@yahoo.fr
authors.forename: Guillaume
authors.initials: G
authors.lastname: Mahé
authors.forename: Firas
authors.initials: F
authors.lastname: Haj-Yassin
authors.forename: Pascal
authors.initials: P
authors.lastname: Rousseau
authors.forename: Anne
authors.initials: A
authors.lastname: Humeau
authors.forename: Sylvain
authors.initials: S
authors.lastname: Durand
authors.forename: Georges
authors.initials: G
authors.lastname: Leftheriotis
authors.forename: Pierre
authors.initials: P
authors.lastname: Abraham
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001783:Blood Flow Velocity; D001794:Blood Pressure; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D017078:Laser-Doppler Flowmetry / Q000295:instrumentation*; D007834:Lasers; D008297:Male; D008833:Microcirculation; D011237:Predictive Value of Tests; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply*; D013997:Time Factors