Fig. 8.

DCS and DRS skin results—occlusion studies were performed on all pigs using a Hoffman clamp placed over the artery. A skin patch was secured to the artery downstream from the Hoffman clamp via sutures [see Fig. 2(c)]. For pigs 3 and 4, the study began with the Hoffman clamp fully opened (3.2 mm). Incremental clamp tightening ($-0.4\mathrm{mm}$) occurred every minute after the first 2 min, with full occlusion reached at 8 min. After 10 min, incremental clamp untightening ($+0.4\mathrm{mm}$) occurred every minute until the clamp reached its original position (3.2 mm). (a) and (b) display DCS ${\tau }_{1/2}$ values calculated from autocorrelation curves measured at skin sites on pigs 1 to 4 using 2- and 5-mm source–detector separations, respectively. (c) and (d) display hemodynamic variables, total [HbT], and ${\mathrm{StO}}_2$ extracted from DRS spectra measured at skin sites on pigs 1 to 4. After DRS data acquisition on pig 2, the surgeon reported spontaneous venous congestion in the flap.