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Pressure-distension relationship in arteries and arterioles in response to 5 wk of horizontal bedrest
Karolinska Inst, Swedish Def Res Agcy.
Karolinska Inst, Swedish Def Res Agcy.
Jozef Stefan Inst, Dept Automat Biocybernet & Robot.
2008 (English)In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 295, no 3, H1296-H1302 p.Article in journal (Refereed) Published
Abstract [en]

We hypothesized that exposure to prolonged recumbency (bedrest), and thus reductions of intravascular pressure gradients, increases pressure distension in arteries/arterioles in the legs. Ten subjects underwent 5 wk of horizontal bedrest. Pressure distension was investigated in arteries and arterioles before and after the bedrest, with the subject seated or supine in a hyperbaric chamber with either one arm or a lower leg protruding through a hole in the chamber door. Increased pressure in the vessels of the arm/leg was accomplished by increasing chamber pressure. Vessel diameter and flow were measured in the brachial and posterior tibial arteries using Doppler ultrasonography. Electrical tissue impedance was measured in the test limb. Bedrest increased (P < 0.01) pressure distension threefold in the tibial artery (from 8 +/- 7% to 24 +/- 11%) and by a third (P < 0.05) in the brachial artery (from 15 +/- 9% to 20 +/- 10%). The pressure-induced increase in tibial artery flow was more pronounced (P < 0.01) after (50 +/- 39 ml/min) than before (13 +/- 23 ml/min) bedrest, whereas the brachial artery flow response was unaffected by bedrest. The pressure-induced decrease in tissue impedance in the leg was more pronounced (P < 0.01) after (16 +/- 7%) than before (10 +/- 6%) bedrest, whereas bedrest did not affect the impedance response in the arm. Thus, withdrawal of the hydrostatic pressure gradients that act along the blood vessels in erect posture markedly increases pressure distension in dependent arteries and arterioles.

Place, publisher, year, edition, pages
2008. Vol. 295, no 3, H1296-H1302 p.
Keyword [en]
gravity, microgravity, vascular compliance, vascular deconditioning, vascular stiffness
Identifiers
URN: urn:nbn:se:kth:diva-25950DOI: 10.1152/ajpheart.00576.2008ISI: 000258949200049PubMedID: 18660441OAI: oai:DiVA.org:kth-25950DiVA: diva2:361106
Note
QC 20101108Available from: 2010-11-08 Created: 2010-11-08 Last updated: 2017-12-12Bibliographically 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.
Series
Trita-STH : report, ISSN 1653-3836 ; 2010:5
Keyword
arterial stiffness, venous distensibility, venous flow characteristics, bedrest, pressure training
National Category
Physiology
Identifiers
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)
Opponent
Supervisors
Note
medicine doktorsexamen QC 20101109Available from: 2010-11-09 Created: 2010-11-08 Last updated: 2012-03-20Bibliographically approved

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