Topographic mapping of the cutaneous microcirculation using two outputs of laser-Doppler flowmetry: flux and the concentration of moving blood cells.

Using a "needle" probe in a template probe holder, we measured the flux and the concentration of moving red blood cell (CMBC) outputs from a Perimed (PF2B) laser-Doppler instrument at 1-mm2 contiguous sites in a 8 x 8-mm area on the flexor forearm of three subjects. Using the means of the flux and CMBC recorded at each spot, a topographic contour map was constructed for each of these parameters. Viewing the two maps together, sites with four different combinations of flux and CMBC could be identified. Trephine biopsies (2 mm) of three representative sites in each subject were performed and the upper plexus was reconstructed in 3 dimensions from serial sections. High flux/high-to-medium CMBC sites were found over the spot where the ascending arterioles entered the upper plexus. Medium flux/medium-to-low CMBC sites and low flux/medium CMBC sites were found in the peripheral part of the vascular unit that was fed by the ascending arteriole. The low flux/low CMBC sites were relatively avascular zones. Video imaging of the upper plexus in the forearm showed the same overall vascular pattern as the contour maps. The highest flux and CMBC signals were recorded when horizontally oriented vessels were present in the upper third of the plexus (400-650 microns below the stratum corneum). Topographic mapping will allow one to selectively identify different microvascular areas in the skin for physiological studies.