RESULTS: Carotid blood flow measurements were performed twice by each physician on 42 different occasions that included 24 patients. Patient ages average was 64.2 (+/-21.1) years, their BMI was 31.3 (+/- 10.4) kg per meter square, most patients were in regular heart rhythm (95%), and spontaneously breathing (72%). When ventilated, the average tidal volume was 7 (+/- 0.8) cc per kg ideal body weight. Twenty percent or less variability in carotid blood flow was seen in 45% of the measurements. While 50% or less variability was seen in 80% of the measurements. When evaluating each of the individual physicians separately, similar numbers were seen (42.8% and 85.7% for physician 1, and 47.6% and 73.8% for physician 2, respectively). There was no significant difference in the mean of the measurements performed by the 2 physicians when compared using t-test (p 0.06).