Fig. 7.

${\tau }_{1/2}$ values calculated from autocorrelation curves collected at artery sites on pigs 1, 2, 3, and 4—occlusion studies were performed on all animals using a Hoffman clamp placed over the artery. Each study began with the Hoffman clamp fully opened (3.2 mm). Incremental tightening of the clamp ($-0.4\mathrm{mm}$) occurred every minute after the first 2 min, with full occlusion reached at 8 min for pigs 1, 3, and 4—for pig 2, full occlusion was reached after 7 min. For pig 1, the fully occluded state was maintained for 4 min, after which, incremental untightening ($+0.4\mathrm{mm}$) of the clamp occurred every minute until the clamp reached its original position (3.2 mm). For pigs 2, 3, and 4, the fully occluded state was only maintained for 2 min. (a) A probe was secured to the artery downstream from the Hoffman clamp via sutures [see Fig. 2(d)]. Only pigs 2 and 3 recorded a significant arterial response during the occlusion study. (b) A probe was secured to the muscle via sutures [see Fig. 2(c)]. Pigs 1 and 2 demonstrated considerably more noise at the muscle site than at any other tissue site. Pig 4 demonstrated the greatest response to the occlusion protocol; however, it was difficult to measure a response at the muscle site for all four animals.