Effects of posture on shear rates in human brachial and superficial femoral arteries

1 Health and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania; 2 Department of Biomedical Sciences, University of Missouri, Columbia, Missouri; and 3 Department of Health and Kinesiology, Purdue University, West Lafayette, Indiana Submitted 24 September 2007 ; accepted in final form 28 January 2008 Shear rate is significantly lower in the superficial femoral compared with the brachial artery in the supine posture. The relative shear rates in these arteries of subjects in the upright posture (seated and/or standing) are unknown. The purpose of this investigation was to test the hypothesis that upright posture (seated and/or standing) would produce greater shear rates in the superficial femoral compared with the brachial artery. To test this hypothesis, Doppler ultrasound was used to measure mean blood velocity (MBV) and diameter in the brachial and superficial femoral arteries of 21 healthy subjects after being in the supine, seated, and standing postures for 10 min. MBV was significantly higher in the brachial compared with the superficial femoral artery during upright postures. Superficial femoral artery diameter was significantly larger than brachial artery diameter. However, posture had no significant effect on either brachial or superficial femoral artery diameter. The calculated shear rate was significantly greater in the brachial (73 ± 5, 91 ± 11, and 97 ± 13 s –1 ) compared with the superficial femoral (53 ± 4, 39 ± 77, and 44 ± 5 s –1 ) artery in the supine, seated, and standing postures, respectively. Contrary to our hypothesis, our current findings indicate that mean shear rate is lower in the superficial femoral compared with the brachial artery in the supine, seated, and standing postures. These findings of lower shear rates in the superficial femoral artery may be one mechanism for the higher propensity for atherosclerosis in the arteries of the leg than of the arm. atherosclerosis; conduit artery diameter; leg and arm vasculature; lesion formation Address for reprint requests and other correspondence: S. C. Newcomer, Purdue Univ., Dept. of Health and Kinesiology, Lambert Fieldhouse, 800 W. Stadium Ave., West Lafayette, IN 47907 (e-mail: snewcome{at}purdue.edu )