Enhanced flow-dependent vasodilatation after bed rest, a possible mechanism for orthostatic intolerance in humans

Bonnin, Philippe; Driss, Ahmed Ben; Bénessiano, Joëlle; Traon, Anne Pavy-Le; Maillet, A.; Lévy, Bernard

doi:10.1007/s004210100483

Cited by 40 publications

(50 citation statements)

References 17 publications

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“…Although not significant, a trend toward an increase was still evident when FMD was corrected for the maximal hyperemic shear rate stimulus (see fig 2C). An increased relative FMD response in deconditioned arteries is also reported in recent studies using different human models for physical inactivity such as chronic SCI, 7 bedrest, 16 and unilateral lower-limb suspension.…”

Section: Endothelial Functionsupporting

confidence: 72%

“…15 Previous studies have shown that this FMD response is enhanced or at least preserved in arteries after a period of deconditioning. 7,14,16 The finding of an enhanced FMD in deconditioned arteries is surprising, because it has been shown previously that FMD also increases after exercise training. 17,18 These findings may imply that vascular adaptations to deconditioning are not simply the opposite of exercise and that a different mechanism might be involved.…”

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confidence: 96%

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Rapid and Extensive Arterial Adaptations After Spinal Cord Injury

Groot¹,

Bleeker²,

Kuppevelt³

et al. 2006

Archives of Physical Medicine and Rehabilitation

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Objective: To assess the time course of adaptations in leg vascular dimension and function within the first 6 weeks after a spinal cord injury (SCI).Design: Longitudinal study design. Setting: University medical center and rehabilitation clinic. Participants: Six men were studied serially at 1, 2, 3, 4, and 6 weeks after SCI.Interventions: Not applicable. Main Outcome Measures: Diameter, blood flow, and shear rate levels of the common femoral artery (CFA), superficial femoral artery (SFA), brachial artery, and carotid artery were measured with echo Doppler ultrasound (diameter, blood flow, shear rate). Endothelial function in the SFA was measured with flow-mediated dilation (FMD). In addition, leg volume and blood pressure measurements were performed.Results: Femoral artery diameter (CFA, 25%; SFA, 16%; PϽ.01) and leg volume (22%, PϽ.01) decreased simultaneously, and these reductions were largely accomplished within 3 weeks postinjury. Significant increases were observed for basal shear rate levels (64% increase at week 3; 117% increase at week 6; PϽ.01), absolute FMD responses (8% increase at week 3, 23% increase at week 6; PϽ.05) and relative FMD responses (26% increase at week 3, 44% increase at week 6; PϽ.001).Conclusions: Our findings show a rapid onset of adaptations in arterial dimension and function to extreme inactivity in humans. Vascular adaptations include extensive reductions in femoral diameter and leg volume, as well as increased basal shear rate levels and FMD responses, which all appear to be largely accomplished within 3 weeks after an SCI.

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Section: Endothelial Functionsupporting

confidence: 72%

mentioning

confidence: 96%

Rapid and Extensive Arterial Adaptations After Spinal Cord Injury

Groot¹,

Bleeker²,

Kuppevelt³

et al. 2006

Archives of Physical Medicine and Rehabilitation

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“…In humans, a recent bed-rest study demonstrated that plasma nitrate and nitrite concentration, an indicator of endogenous NO production, was decreased after 14 days of bed-rest immobilization (25). However, Bonnin et al (4) reported an enhanced FMD response in the BA after 7 days of bed-rest deconditioning. The authors reported no changes in resting and hyperemic parameters and no changes in endothelium independent vasodilatation from pre-to post-bed rest, which seems to indicate that the enhanced FMD cannot be attributed to differences in the stimulus for NO release or to an increased sensitivity of arterial smooth muscle cell for NO.…”

Section: Discussionmentioning

confidence: 98%

Preserved flow-mediated dilation in the inactive legs of spinal cord-injured individuals

Groot¹,

Poelkens²,

Kooijman³

et al. 2004

American Journal of Physiology-Heart and Circulatory Physiology

105

110

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.-The aim of the study was to assess endothelial function, measured by flow-mediated dilation (FMD), in an inactive extremity (leg) and chronically active extremity (arm) within one subject. Eleven male spinal cord-injured (SCI) individuals and eleven male controls (C) were included. Echo Doppler measurements were performed to measure FMD responses after 10 and 5 min of arterial occlusion of the leg (superficial femoral artery, SFA) and the arm (brachial artery, BA), respectively. A nitroglycerine spray was administered to determine the endothelium independent vasodilatation in the SFA. In the SFA, relative changes in FMD were significantly enhanced in SCI compared with C (SCI: 14.1 Ϯ 1.3%; C: 9.2 Ϯ 2.3%), whereas no differences were found in the BA (SCI: 12.5 Ϯ 2.9%; C: 14.2 Ϯ 3.3%). Because the FMD response is directly proportional to the magnitude of the stimulus, the FMD response was also expressed relative to the shear rate. No differences between the groups were found for the FMD-to-shear rate ratio in the SFA (SCI:0.061 Ϯ 0.023%/s Ϫ1 ; C: 0.049 Ϯ 0.024%/s Ϫ1 ), whereas the FMD-to-shear rate ratio was significantly decreased in the BA of SCI individuals (SCI: 0.037 Ϯ 0.01%/s Ϫ1 ; C: 0.061 Ϯ 0.027%/s Ϫ1 ). The relative dilatory response to nitroglycerine did not differ between the groups. (SCI: 15.6 Ϯ 2.0%; C: 13.4 Ϯ 2.3%). In conclusion, our results indicate that SCI individuals have a preserved endothelial function in the inactive legs and possibly an attenuated endothelial function in the active arms compared with controls. vascular endothelial function; deconditioning; ultrasound THE ENDOTHELIUM plays an essential role in vascular homeostasis and is able to respond to physical and chemical stimuli by the synthesis and release of vasoactive, thromboregulatory, and growth factor substances (37). Impaired endothelial function has been suggested as a key early event in the development of atherosclerosis, and a high correlation between endothelial dysfunction and risk factors for cardiovascular diseases, including hypertension, hypercholesterolemia, cigarette smoking, diabetes, and aging, has been reported (6 -8, 12, 29, 33, 47, 48). Besides the above-mentioned traditional risk factors, it is well known that physical inactivity is associated with an increased risk of developing cardiovascular diseases (32). However, at present, the relationship between inactivity and endothelial dysfunction is not clear. In individuals with paraplegia, the part of the body below the lesion level is paralyzed and thus extremely inactive (20,39). In contrast, the upper limbs are often relatively active because the arms are used for ambulation due to their wheelchair-bound life-style (43). A spinal cord injury (SCI), therefore, offers a unique "human model of nature" to assess peripheral vascular adaptations to inactivity (legs) and activity (arms) on endothelial function within one subject.Healthy vessels are capable of accommodating to an increase in blood flow by dilating the internal vessel diameter, a phenomenon called fl...

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“…However, previous studies have recruited similar or smaller groups and have typically examined the effects of 5 to 7 days of bed rest only. 47,48 Because the magnitude of physical inactivity is time dependent, 49 60 days clearly resulted in a large impact on the vasculature. The profound stimulus of complete bed rest, 49 combined with the excellent reproducibility of our technique, 22 allowed us to detect these important findings in a relatively small group of participants.…”

Section: Van Duijnhoven Et Al Bed Rest and Conduit Artery Remodeling 243mentioning

confidence: 99%

Impact of Bed Rest on Conduit Artery Remodeling

et al. 2010

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Abstract-Physical inactivity is a potent stimulus for vascular remodeling, leading to a marked decrease in conduit artery diameter. However, little is known about the impact of physical inactivity on artery wall thickness or wall:lumen ratio or the potential of exercise countermeasures to modify artery wall thickness. The purpose of the study was to examine the impact of 60 days of bed rest, with or without exercise countermeasures, on carotid and superficial femoral artery wall thickness. Eighteen men were assigned to bed rest (second Berlin Bed Rest Study) and randomly allocated to control, resistive exercise, or resistive vibration exercise. Both exercise countermeasures were applied 3 times per week while the subjects were in the supine position on the bed. Sonography was used to examine baseline diameter and wall thickness of the carotid and femoral arteries. Bed rest decreased diameter of the superficial femoral artery (Pϭ0.001) but not the carotid artery (Pϭ0.29). Bed rest induced a significant increase in carotid and superficial femoral artery wall thickness (Pϭ0.007 and 0.03) and wall:lumen ratio (Pϭ0.009 and 0.001). Exercise prevented the increase in wall thickness of the carotid artery. In addition, exercise partly prevented the increased wall:lumen ratio in the superficial femoral artery. In conclusion, 8 weeks of bed rest resulted in Ϸ20% increase in conduit artery wall thickness. Exercise countermeasures completely (carotid artery) or partly (superficial femoral artery) abolished the increase in wall thickness. These findings suggest that conduit artery wall thickness, a vascular characteristic associated previously with atherosclerosis, can rapidly adapt to physical inactivity and exercise in humans. (Hypertension. 2010;56:240-246.)

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Enhanced flow-dependent vasodilatation after bed rest, a possible mechanism for orthostatic intolerance in humans

Cited by 40 publications

References 17 publications

Rapid and Extensive Arterial Adaptations After Spinal Cord Injury

Rapid and Extensive Arterial Adaptations After Spinal Cord Injury

Preserved flow-mediated dilation in the inactive legs of spinal cord-injured individuals

Impact of Bed Rest on Conduit Artery Remodeling

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