title: Comparison of laser speckle contrast imaging with laser Doppler for assessing microvascular function.
abstract: OBJECTIVE
  To compare the inter-day reproducibility of post-occlusive reactive hyperaemia (PORH) and sympathetic vasomotor reflexes assessed by single-point laser Doppler flowmetry (SP-LDF), integrating-probe LDF (IP-LDF) and laser speckle contrast imaging (LSCI), and the spatial variability of PORH assessed by IP-LDF and LSCI. We also evaluated the relationship between IP-LDF and LSCI perfusion values across a broad range of skin blood flows.
  
  
  METHODS
  Eighteen healthy adults (50% male, age 27 ± 4 years) participated in this study. Using SP-LDF, IP-LDF and LSCI, indices of skin blood flow were measured on the forearm during PORH (1-, 5- and 10-min occlusions) and on the finger pad during inspiratory gasp and cold pressor tests. These tests were repeated 3-7 days later. Data were converted to cutaneous vascular conductance (CVC; laser Doppler flow/mean arterial pressure) and expressed as absolute and relative changes from pre-stimulus CVC (ΔCVC(ABS) and ΔCVC(REL), respectively), as well as normalised to peak CVC for the PORH tests. Reproducibility was expressed as within-subjects coefficients of variation (CV, in %) and intraclass correlation coefficients.
  
  
  RESULTS
  The reproducibility of PORH on the forearm was poorer when assessed with SP-LDF and IP-LDF compared to LSCI (e.g., CV for 5-min PORH ΔCVC(ABS)=35%, 27% and 19%, respectively), with no superior method of data expression. In contrast, the reproducibility of the inspiratory gasp and cold pressor test responses on the finger pad were better with SP-LDF and IP-LDF compared to LSCI (e.g., CV for inspiratory gasp ΔCVC(REL)=13%, 7% and 19%, respectively). The spatial variability of PORH responses was poorer with IP-LDF compared to LSCI (e.g., CV ranging 11-35% versus 3-16%, respectively). The association between simultaneous LSCI and IP-LDF perfusion values was non-linear.
  
  
  CONCLUSIONS
  The reproducibility of cutaneous PORH was better when assessed with LSCI compared to SP-LDF and IP-LDF; probably due to measuring larger skin areas (lower inter-site variability). However, when measuring sympathetic vasomotor reflexes on the finger pad, reproducibility was better with SP-LDF and IP-LDF, perhaps due to the high sensitivity of LSCI to changes in skin blood flow at low levels.
authors.affiliation: Centre for Sport and Exercise Science, Sheffield Hallam University, A125 Collegiate Hall, Sheffield, S10 2BP, UK. g.tew@shu.ac.uk
authors.forename: Garry A
authors.initials: GA
authors.lastname: Tew
authors.forename: Markos
authors.initials: M
authors.lastname: Klonizakis
authors.forename: Helen
authors.initials: H
authors.lastname: Crank
authors.forename: J David
authors.initials: JD
authors.lastname: Briers
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Hodges
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D003080:Cold Temperature; D004739:England; D005260:Female; D005385:Fingers; D005542:Forearm; D006439:Hemodynamics; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D001239:Inhalation; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation; D055806:Microvessels / Q000294:innervation / Q000503:physiopathology*; D015588:Observer Variation; D055420:Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D012018:Reflex; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012867:Skin / Q000098:blood supply*; D013564:Sympathetic Nervous System / Q000503:physiopathology; D013997:Time Factors; D055815:Young Adult