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Increased distensibility in dependent veins following prolonged bedrest
Karolinska Inst, Swedish Def Res Agcy.
Karolinska Inst, Swedish Def Res Agcy.
Karolinska Inst, Swedish Def Res Agcy.
2009 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 106, no 4, 547-554 p.Article in journal (Refereed) Published
Abstract [en]

Displacement of blood to the lower portion of the body that follows a postural transition from recumbent to erect is augmented by a prolonged period of recumbency (bedrest). Information is scarce as to what extent this augmented blood-volume shift to dependent veins is attributable to increased distensibility of the veins. Accordingly, we studied the effect of 5 weeks of horizontal bedrest on the pressure-distension relationship in limb veins. Elevation of venous distending pressure was induced by exposure of the body except the tested limb to supra-atmospheric pressure with the subject seated in a pressure chamber with one arm, or supine with a lower leg, protruding through a hole in the chamber door. Diameter changes in response to an increase of intravenous pressure (distensibility) from 60 to about 140 mmHg were measured in the brachial and posterior tibial veins using ultrasonographic techniques. Prior to bedrest, the distensibility was substantially less in the tibial than in the brachial vein. Bedrest increased (P < 0.01) pressure distension in the tibial vein by 86% from 7 +/- A 3% before to 13 +/- A 3% after bedrest. In the brachial vein, bedrest increased (P < 0.05) pressure distension by 36% from 14 +/- A 5% before to 19 +/- A 5% after bedrest. Thus, removal of the gravity-dependent pressure components that act along the blood vessels in erect posture increases the distensibility of dependent veins.

Place, publisher, year, edition, pages
2009. Vol. 106, no 4, 547-554 p.
Keyword [en]
Sustained bedrest, Venous compliance, Gravity, Blood-volume distribution, Vascular deconditioning
URN: urn:nbn:se:kth:diva-25954DOI: 10.1007/s00421-009-1044-3ISI: 000266814800008PubMedID: 19347352OAI: diva2:361112
QC 20101108Available from: 2010-11-08 Created: 2010-11-08 Last updated: 2010-11-09Bibliographically approved
In thesis
1. Distensibility in Arteries, Arterioles and Veins in Humans: Adaptation to Intermittent or Prolonged Change in Regional Intravascular Pressure
Open this publication in new window or tab >>Distensibility in Arteries, Arterioles and Veins in Humans: Adaptation to Intermittent or Prolonged Change in Regional Intravascular Pressure
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present series of in vivo experiments in healthy subjects, were performed to investigate wall stiffness in peripheral vessels and how this modality adapts to iterative increments or sustained reductions in local intravascular pressures. Vascular stiffness was measured as changes in arterial and venous diameters, and in arterial flow, during graded increments in distending pressures in the vasculature of an arm or a lower leg. In addition, effects of intravascular pressure elevation on flow characteristics in veins, and on limb pain were elucidated. Arteries and veins were stiffer (i.e. pressure distension was less) in the lower leg than in the arm. The pressure-induced increase in arterial flow was substantially greater in the arm than in the lower leg, indicating a greater stiffness in the arterioles of the lower leg. Prolonged reduction of intravascular pressures in the lower body, induced by 5 wks of sustained horizontal bedrest (BR), decreased stiffness in the leg vasculature. BR increased pressure distension in the tibial artery threefold and in the tibial vein by 86 %. The pressure-induced increase in tibial artery flow was greater post bedrest, indicating reduced stiffness in the arterioles of the lower leg. Intermittent increases of intravascular pressures in one arm (pressure training; PT) during a 5-wk period decreased vascular stiffness. Pressure distension and pressure-induced flow in the brachial artery were reduced by about 50 % by PT. PT reduced pressure distension in arm veins by 30 to 50 %. High intravascular pressures changed venous flow to arterial-like pulsatile patterns, reflecting propagation of pulse waves from the arteries to the veins either via the capillary network or through arteriovenous anastomoses. High vascular pressures induced pain, which was aggravated by BR and attenuated by PT; the results suggest that the pain was predominantly caused by vascular overdistension. In conclusion, vascular wall stiffness constitutes a plastic modality that adapts to meet demands imposed by a change in the prevailing local intravascular pressure. That increased intravascular pressure leads to increased arteriolar wall stiffness supports the notion that local pressure load may serve as a “prime mover” in the development of vascular changes in hypertension.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 51 p.
Trita-STH : report, ISSN 1653-3836 ; 2010:5
arterial stiffness, venous distensibility, venous flow characteristics, bedrest, pressure training
National Category
urn:nbn:se:kth:diva-25965 (URN)978-91-7415-778-9 (ISBN)
Public defence
2010-11-26, sal 3:221, Alfreds Nobels Alle 10, Flemingsberg, Huddinge, 09:00 (Swedish)
medicine doktorsexamen QC 20101109Available from: 2010-11-09 Created: 2010-11-08 Last updated: 2012-03-20Bibliographically approved

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