Comparative reproducibility of dermal microvascular blood flow changes in response to acetylcholine iontophoresis, hyperthermia and reactive hyperaemia.
ABSTRACT Laser Doppler fluxmetry (LDF) can non-invasively measure skin microvascular changes in response to acetylcholine (ACh), local heating of the skin and reactive hyperaemia following arterial occlusion. Various studies have used microvascular changes in response to these stimuli, especially ACh iontophoresis and local heating, as a surrogate marker of endothelial function. There are few data in the literature regarding the comparative reproducibility of microvascular perfusion changes induced by the three stimuli. The aim of this study was to systematically assess and compare the reproducibility of skin microcirculatory function in response to each of these challenges. Ten healthy non-smoking subjects (seven males) median age 36 years (range 23-46), with no history of hypertension, diabetes, coronary artery disease or any connective tissue disorder, were studied. Changes in skin microcirculation in response to ACh iontophoresis, local heating of the skin and post-occlusive reactive hyperaemia, on two separate days (median 31, range 11-42 days), were assessed in all subjects. We measured three parameters: the change in perfusion from baseline perfusion (peak minus baseline perfusion), the relative percentage change in perfusion from baseline (peak--baseline)/baseline x 100 (%) and also the time-to-peak perfusion. The reproducibility of the change in perfusion had coefficients of variation (CV) of 9.3% for local skin heating, 19.4% for reactive hyperaemia and 25.5% for ACh iontophoresis. The relative percentage change in perfusion from baseline was more variable with CVs ranging from 23% to 39%. The coefficient of variation of time-to-peak perfusion was 7.0% for heating, 15.1% for reactive hyperaemia and 10.4% for ACh iontophoresis. We have shown that microcirculatory changes measured by the change in perfusion from baseline and time-to-peak perfusion in response to ACh, post-occlusive reactive hyperaemia and local skin heating had good reproducibility when carried out in a controlled environment with a standardized protocol. Relative change in perfusion had relatively poor reproducibility. The change in perfusion and time-to-peak perfusion for local skin heating were the most reproducible overall.
Article: Reproducibility of non-invasive assessment of skin endothelial function using laser Doppler flowmetry and laser speckle contrast imaging.[show abstract] [hide abstract]
ABSTRACT: Endothelial dysfunction precedes atherosclerosis. Vasodilation induced by acetylcholine (ACh) is a specific test of endothelial function. Reproducibility of laser techniques such as laser-Doppler-flowmetry (LDF) and Laser-speckle-contrast-imaging (LSCI) to detect ACh vasodilation is debated and results expressions lack standardization. We aimed to study at a 7-day interval (i) the inter-subject reproducibility, (ii) the intra-subjects reproducibility, and (iii) the effect of the results expressions over variability. Using LDF and LSCI simultaneously, we performed two different ACh-iontophoresis protocols. The maximal ACh vasodilation (peak-ACh) was expressed as absolute or normalized flow or conductance values. Inter-subject reproducibility was expressed as coefficient of variation (inter-CV,%). Intra-subject reproducibility was expressed as within subject coefficients of variation (intra-CV,%), and intra-class correlation coefficients (ICC). Fifteen healthy subjects were included. The inter-subject reproducibility of peak-ACh depended upon the expression of the results and ranged from 55% to 162% for LDF and from 17% to 83% for LSCI. The intra-subject reproducibility (intra-CV/ICC) of peak-ACh was reduced when assessed with LSCI compared to LDF no matter how the results were expressed and whatever the protocol used. The highest intra-subject reproducibility was found using LSCI. It was 18.7%/0.87 for a single current stimulation (expressed as cutaneous vascular conductance) and 11.4%/0.61 for multiple current stimulations (expressed as absolute value). ACh-iontophoresis coupled with LSCI is a promising test to assess endothelial function because it is reproducible, safe, and non-invasive. N°: NCT01664572.PLoS ONE 01/2013; 8(4):e61320. · 4.09 Impact Factor
Article: Relevance of Laser Doppler and Laser Speckle Techniques for Assessing Vascular Function: State of the Art and Future Trends.[show abstract] [hide abstract]
ABSTRACT: In clinical and research applications, the assessment of vascular function has become of major importance to evaluate and follow the evolution of cardiovascular pathologies, diabetes, hypertension, or foot ulcers. Therefore, the development of engineering methodologies able to monitor non-invasively blood vessels activities - such as endothelial function - is a significant and emerging challenge. Laser-based techniques have been used to respond as much as possible to these requirements. Among them, laser Doppler flowmetry (LDF) and laser Doppler imaging (LDI) were proposed a few decades ago. They provide interesting vascular information but possess drawbacks that prevent an easy use in some clinical situations. Recently, the laser speckle contrast imaging (LSCI) technique, a non-invasive camera-based tool, was commercialized and overcomes some of the LDF and LDI weaknesses. Our paper describes how - using engineering methodologies - LDF, LDI and LSCI can meet the challenging clinician needs in assessing vascular function, with a special focus on the state of the art and future trends.IEEE transactions on bio-medical engineering 01/2013; · 2.15 Impact Factor