Subcutaneous blood flow over 24-hour periods in patients with severe leg ischaemia

This paper describes a method for studying the clearance of 133Xenon from the subcutaneous tissue of the calf and foot over 24-h periods. The average blood flow over this period can be estimated from the clearance constant obtained. Two series of measurement of the radioactivity are made, the first 2 h after the injection of 1-2 mCi 133Xenon in saline and the second 18-24 h later. The distance between the detector and the depot is reproduced using a cylinder 20 cm long. The median washout rate of the isotope (k) in 25 patients was 2.57 X 10(-3) min-1 for the calf and 2.39 X 10(-9) min-1 for the foot. The median difference between repeated measurements in the same patient ws 0.24 X 10(-3) min-1 in the calf and 0.43 X 10(-3) min-1 in the foot. This method, which can be used to estimate the average blood flow over 24 h while the patient undertakes his normal activities, should be useful in assessing the effect of therapy on the blood flow to the limb.