2. To measure sublingual capillary glycocalyx and density, videos (10 sec) of sublingual capillaries in 2 areas lateral of the frenulum and 3-4 cm anterior to the tongue base will be recorded, using orthogonal polarization spectral (OPS) and side stream dark field (SDF) imaging [Hubble et al.]. In our hands, the intra- and inter-observer reproducibility of capillary density is 10.2 and 13.4% respectively. The erythrocyte-endothelium gap is the gold standard for glycocalyx measurement in vivo [Nieuwdorp et al.], as endothelial glycocalyx allows limited access to erythrocytes. The perfused boundary region (PBR) hereby reflects glycocalyx thickness and integrity, increased PBR glycocalyx loss.