Postural changes in capillary pressure in the hallux of healthy volunteers

1 Department of Vascular Surgery, Academic Medical Center, University of Amsterdam, 1100 DE Amsterdam; 2 Department of Anesthesiology and Intensive Care, St. Antonius Hospital, 3430 EM Nieuwegein; and 3 Department of Surgery, University Hospital Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands Submitted 27 February 2003 ; accepted in final form 23 June 2003 Capillary circulation is delicately regulated by microvascular constriction mechanisms, thereby controlling capillary perfusion and transmural pressure. The influence of posture on capillary flow has been investigated in both diseased and healthy people. However, its influence on capillary pressure has rarely been investigated. We measured capillary pressures in the supine and sitting positions in the hallux of healthy volunteers. The capillaries in the eponychium of the hallux were punctured by using a micropipette connected to a micropressure system (900A, WPI). Also, peripheral arterial and venous pressures were measured in both positions. The rise in systolic capillary pressure from supine to sitting position (32 mmHg; from 39 to 71 mmHg, respectively) was significantly ( P < 0.001) smaller than the rise in systolic arterial toe pressure (57 mmHg, from 87 to 144 mmHg, respectively) and venous pressure (41 mmHg, from 26 mmHg to 67 mmHg, respectively). This study shows that the postural rise in precapillary arteriolar pressure is not completely transmitted to the capillaries, probably because of activation of peripheral vasoconstriction mechanisms. microcirculation; capillaries; blood pressure; regional blood flow; vasoconstriction Address for reprint requests and other correspondence: D. T. Ubbink, Dept. of Vascular Surgery, Academic Medical Center, Meibergdreef 9, PO Box 22700, 1100 DE Amsterdam, The Netherlands (E-mail: d.ubbink{at}amc.uva.nl ).