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This Article Full Text Full Text (PDF) All Versions of this Article: 295/3/H1296    most recent 00576.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Eiken, O. Articles by Mekjavic, I. B. Search for Related Content PubMed PubMed Citation Articles by Eiken, O. Articles by Mekjavic, I. B.

Pressure-distension relationship in arteries and arterioles in response to 5 wk of horizontal bedrest

¹Swedish Defence Research Agency, Karolinska Institutet, Stockholm, Sweden; and ²Department of Automation Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia

Submitted 2 June 2008 ; accepted in final form 22 July 2008

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.

gravity; microgravity; vascular compliance; vascular deconditioning; vascular stiffness