Increased distensibility in dependent veins following prolonged bedrest

Kölegård, Roger; Mekjavic, Igor B.; Eiken, Ola

doi:10.1007/s00421-009-1044-3

Cited by 19 publications

(24 citation statements)

References 31 publications

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“…Venous pressure-distension test Pressure-distension relationships in arm veins were determined by the use of an experimental model described in detail elsewhere Kölegård 2001, 2004;Kölegård et al 2009). BrieXy, to increase the venous distending pressure (DP) locally in one arm (test arm), the subject was seated inside a hyperbaric pressure chamber with the test arm protruding to the outside via a hole in the chamber door.…”

Section: Methodsmentioning

confidence: 99%

“…Consequently, DP in the veins of the test arm was assumed to equal pressure applied in the chamber (cf. Kölegård 2001, 2004;Kölegård et al 2009). …”

Section: Analysesmentioning

confidence: 95%

“…The DP transition from 0 mmHg (atmospheric pressure) to 30 mmHg is assumed to include the Wlling phase during which the veins restore their circular lumen, whereas diameter changes occurring with further elevations of venous pressure represent true elastic distension of the venous walls Kölegård 2001, 2004;Kölegård et al 2009). In the present study, venous pressure distension (or distensibility) was deWned as the relative change in lumen diameter at the site proximal of the valve, in response to the DP elevation from 30 to 180 mmHg.…”

Section: Analysesmentioning

confidence: 99%

“…It appears that regular exposures to gravity-induced increments in transmural pressure are needed to maintain the elevated stiVness in dependent veins. Thus, sustained removal of the hydrostatic pressure gradients acting along longitudinally oriented veins by exposure to 5 weeks of horizontal bed rest markedly increased the distensibility of the veins in the lower leg (Kölegård et al 2009). Information is however lacking regarding the eVect of prolonged or iterated elevations of transmural pressure on venous distensibility.…”

Section: Introductionmentioning

confidence: 96%

“…It is a common notion that longitudinally oriented veins adapt to cope with the hydrostatic pressure gradients acting along the vessels inasmuch as that the repeated exposures to high transmural pressure, associated with life in an upright body position, render the walls of dependent veins stiV, thereby limiting pressureinduced venous blood pooling (von Kügelgen 1955;Zhang 2001;Eiken and Kölegård 2004;Kölegård et al 2009). Data supporting the existence of venous pressure adaption in humans stems mainly from cross-sectional studies on regional diVerences in venous wall structure, showing that proximal veins contain more collagen and elastin than do distal veins, which, by contrast, are characterized by a thick smooth muscle layer (von Kügelgen 1955).…”

Section: Introductionmentioning

confidence: 99%

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Distensibility in human veins as affected by 5 weeks of repeated elevations of local transmural pressure

Kölegård

Eiken

2011

Eur J Appl Physiol

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The objectives were to investigate the effects of repeated increments in local intravascular pressure (pressure training; PT) on (1) distensibility in two arm veins, and (2) pain in the arm induced by markedly increased intravascular pressure. Elevation of venous distending pressure (DP) in an arm was induced by placing the subject (n = 8) in a pressure chamber with one arm protruding to the outside via a port in the chamber door, and increasing chamber pressure. During 5 weeks, venous DP in one arm was repeatedly (3 × 40 min/week) increased (65-105 mmHg). Pressure-distension relationships were determined in the brachial and cephalic veins by measuring diameter changes by ultrasonography during stepwise increments in DP to 180 mmHg. In the brachial vein, the diameter change in response to an increase in DP from 30 to 180 mmHg (distensibility) was reduced (P < 0.05) in the pressure-trained arm (11%) compared to that in the control arm before (23%) and after (21%) PT. The cephalic vein showed a similar response with a reduced (P < 0.05) distensibility in the pressure-trained arm (20%) compared to that in the control arm before (29%) and after (25%) PT. At any given DP, arm pain was less (P < 0.05) in the pressure-trained arm than in the control arm before and after PT, presumably reflecting the reduced venous distensibility in the pressure-trained arm. The results support the concept that the distensibility of venous walls adapts to meet the demands imposed by the prevailing local transmural pressures.

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Section: Methodsmentioning

confidence: 99%

“…Consequently, DP in the veins of the test arm was assumed to equal pressure applied in the chamber (cf. Kölegård 2001, 2004;Kölegård et al 2009). …”

Section: Analysesmentioning

confidence: 95%

Section: Analysesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Distensibility in human veins as affected by 5 weeks of repeated elevations of local transmural pressure

Kölegård

Eiken

2011

Eur J Appl Physiol

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A global multiscale mathematical model for the human circulation with emphasis on the venous system

Müller

Toro

2014

Int. J. Numer. Meth. Biomed. Engng.

203

297

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We present a global, closed-loop, multiscale mathematical model for the human circulation including the arterial system, the venous system, the heart, the pulmonary circulation and the microcirculation. A distinctive feature of our model is the detailed description of the venous system, particularly for intracranial and extracranial veins. Medium to large vessels are described by one-dimensional hyperbolic systems while the rest of the components are described by zero-dimensional models represented by differential-algebraic equations. Robust, high-order accurate numerical methodology is implemented for solving the hyperbolic equations, which are adopted from a recent reformulation that includes variable material properties. Because of the large intersubject variability of the venous system, we perform a patient-specific characterization of major veins of the head and neck using MRI data. Computational results are carefully validated using published data for the arterial system and most regions of the venous system. For head and neck veins, validation is carried out through a detailed comparison of simulation results against patient-specific phase-contrast MRI flow quantification data. A merit of our model is its global, closed-loop character; the imposition of highly artificial boundary conditions is avoided. Applications in mind include a vast range of medical conditions. Of particular interest is the study of some neurodegenerative diseases, whose venous haemodynamic connection has recently been identified by medical researchers.

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Effects of long-term head-down-tilt bed rest and different training regimes on the coagulation system of healthy men

et al. 2013

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Immobility plus preexisting chronic disease or acute trauma can activate the coagulation system, thus increasing the risk for thromboembolic events. The effects of long-term bed-rest immobility and microgravity on the coagulation system of healthy persons (e.g., during crewed Mars missions) have not yet been studied. The main objective of the second Berlin BedRest Study (BBR2-2) “Coagulation Part” was to investigate adaptations of the hemostatic system during long-term bed rest (60 days) under simulated microgravity (6° head-down-tilt [6°HDT]) and after mobilization in three different volunteer groups (randomly assigned to CTR= inactive control group; RE= resistive exercise only group; and RVE= resistive exercise with whole-body vibration group). In 24 males (aged 21–45 years), before, during, and after long-term bed rest, key parameters of coagulation were measured from venous blood samples: D-dimer (DD), thrombin–antithrombin III complex (TAT), and prothrombin fragment F1 + 2 (PT-F1 + 2). Additionally, modified rotational thrombelastometry (ROTEM®) analysis was performed. Times of exploratory analyses were as follows: baseline data collection 2 days before bed rest (BDC-2); eight different days of 6°HDT bed rest (HDT1–HDT60), and two different days after reambulation (R + 3 and R + 6). We found significant changes in DD, TAT, and PT-F1 + 2 over the total time course, but no consistent effect of physical interventions (RE, RVE) on these parameters. Notably, no parameter reached levels indicative of intravascular thrombin formation. All ROTEM® parameters remained within the normal range and no pathological traces were found. Sixty days of 6°HDT bed rest are not associated with pronounced activation of the coagulation system indicative of intravascular thrombus formation in healthy volunteers independent of the training type during the bed rest.

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Increased distensibility in dependent veins following prolonged bedrest

Cited by 19 publications

References 31 publications

Distensibility in human veins as affected by 5 weeks of repeated elevations of local transmural pressure

Distensibility in human veins as affected by 5 weeks of repeated elevations of local transmural pressure

A global multiscale mathematical model for the human circulation with emphasis on the venous system

Effects of long-term head-down-tilt bed rest and different training regimes on the coagulation system of healthy men

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