Reproducibility of Non-Invasive Assessment of Skin Endothelial Function Using Laser Doppler Flowmetry and Laser Speckle Contrast Imaging

Abstract

BackgroundEndothelial 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.Methods and ResultsUsing 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).ConclusionACh-iontophoresis coupled with LSCI is a promising test to assess endothelial function because it is reproducible, safe, and non-invasive. N°: NCT01664572.

Assessment of microvascular and metabolic responses in the skin

“…In agreement with a previous study (Puissant et al, 2013), it was found that the image-based techniques, and in particular LSCI, have a lower inter-subject variability compared with LDF. The reproducibility of techniques is important to consider as it impacts on the number of subjects needed to obtain adequate statistical power.…”

“…LSCI is able to scan a larger area of skin (typically 15 x 15 cm) in a time frame of a few seconds while at the same time maintaining a high spatial resolution (0.2 mm/pixel at 25 cm distance). The technique has been shown to have a better reproducibility than LDF (Puissant et al, 2013;Roustit et al, 2010), and this has been attributed to the fact that blood flow changes can be assessed in an area instead of in a single point.…”

Different responses of the retinal and cutaneous microcirculation to transient dysmetabolic conditions

“…This hypothesis has been however challenged by other studies demonstrating a reduction in Ach-induced cutaneous vasodilation by acute hyperhomocysteinemia which could be improved after intervention with a thiol-antioxidant [20,21]. Because the investigated subjects in those studies were comparable with regard to age and health state to our group, the disagreement across studies may possibly be a result of a relative low reproducibility of the technique which critically depends on the applied protocol [22,23].…”

Low-pressure sequential compression of lower limbs enhances forearm skin blood flow

“…The temperature of the sensor was stabilized at 32°C throughout the duration of the recording, except during the six minutes of the hyperT-test. The changes in LDF reflect the modifications in microcirculation; the LDF sensor detects the frequency of the oscillation induced by the Doppler frequency shift of the red blood cells in the skin vasculature and translates the frequency to an intensity oscillation [12]. The LDF signal was continuously transferred to a PC computer equipped with the Perisoft 2.55 Software (Perimed ® , Järfälla, Sweden).…”