Contribution of perfusion pressure to vascular resistance response during head-up tilt. Journal   American journal of physiology. Heart and circulatory physiology. Citation   Am J Physiol Heart Circ Physiol. 281(1):H371-5 Publication date   2001 Jul Authors   Imadojemu VA Lott ME Gleeson K Hogeman CS Ray CA Sinoway LI Investigators   Kevin Gleeson Virginia A. Imadojemu Mary E. Lott Chester A. Ray Lawrence I. Sinoway Grant agencies   National Heart, Lung, and Blood Institute National Center for Research Resources Grants   NHLBI K23 HL-04190 NHLBI K24 HL-04011 NCRR M01 RR-10732 NHLBI R01 HL-58503 MeSH headings   Blood Pressure Tilt-Table Test Vascular Resistance MeSH qualifiers   physiology Abstract   We measured brachial and femoral artery flow velocity in eight subjects and peroneal and median muscle sympathetic nerve activity (MSNA) in five subjects during tilt testing to 40 degrees. Tilt caused similar increases in MSNA in the peroneal and median nerves. Tilt caused a fall in femoral artery flow velocity, whereas no changes in flow velocity were seen in the brachial artery. Moreover, with tilt, the increase in the vascular resistance employed (blood pressure/flow velocity) was greater and more sustained in the leg than in the arm. The ratio of the percent increase in vascular resistance in leg to arm was 2.5:1. We suggest that the greater vascular resistance effects in the leg were due to an interaction between sympathetic nerve activity and the myogenic response. Medline ID   21298856