Changes in leg vein filling and emptying characteristics and leg volumes during long-term head-down bed rest

1997 ◽  
Vol 82 (6) ◽  
pp. 1726-1733 ◽  
Author(s):  
Francis Louisy ◽  
Philippe Schroiff ◽  
Antonio Güell
Keyword(s):  
Bed Rest ◽  
Venous Occlusion ◽  
Arterial Flow ◽  
Flow Index ◽  
Venous Compliance ◽  
Physiological Factors ◽  
Control Value ◽  
Flow Changes ◽  
Mercury Strain Gauge

Louisy, Francis, Philippe Schroiff, and Antonio Güell.Changes in leg vein filling and emptying characteristics and leg volumes during long-term head-down bed rest. J. Appl. Physiol. 82(6): 1726–1733, 1997.—Leg venous hemodynamics [venous distensibility index (VDI), arterial flow index (AFI), half-emptying time (T1/2)], and leg volumes (LV) were assessed by mercury strain-gauge plethysmography with venous occlusion and volometry, respectively, in seven men before, during, and after 42 days of 6° head-down bed rest. Results showed a high increase in VDI up to day 26 of bed rest (+50% vs. control at day 26, P < 0.05), which tended to subside thereafter (+20% increase vs. control value at day 41, P < 0.05). VDI changes were associated with parallel changes in T1/2 (+54% vs. control at day 26 of bed rest, P < 0.05, and +25% vs. control at day 41, P < 0.05) and with a decrease in AFI (−49% at day 41 vs. control, P < 0.05). LV continuously decreased throughout bed rest (−13% vs. control at day 41, P < 0.05) but was correlated with VDI only during the first month of bed rest. These results show that during long-term 6° head-down bed rest alterations of leg venous compliance are associated with impairment of venous emptying capacities and arterial flow. Changes in skeletal muscle mass and fluid shifts may account for venous changes during the first month of bed rest but, subsequently, other physiological factors, to be determined, may also be involved in leg venous hemodynamic alterations.

Effects of 18 days of bed rest on leg and arm venous properties

2004 ◽  
Vol 96 (3) ◽  
pp. 840-847 ◽  
Author(s):  
M. W. P. Bleeker ◽  
P. C. E. De Groot ◽  
J. A. Pawelczyk ◽  
M. T. E. Hopman ◽  
B. D. Levine
Keyword(s):  
Orthostatic Intolerance ◽  
Lower Body Negative Pressure ◽  
Bed Rest ◽  
Venous Occlusion ◽  
Stress Index ◽  
Orthostatic Tolerance ◽  
Venous Compliance ◽  
Venous Flow ◽  
Gravitational Gradients ◽  
Small Change

Venous function may be altered by bed rest deconditioning. Yet the contribution of altered venous compliance to the orthostatic intolerance observed after bed rest is uncertain. The purpose of this study was to assess the effect of 18 days of bed rest on leg and arm (respectively large and small change in gravitational gradients and use patterns) venous properties. We hypothesized that the magnitude of these venous changes would be related to orthostatic intolerance. Eleven healthy subjects (10 men, 1 woman) participated in the study. Before (pre) and after (post) 18 days of 6° head-down tilt bed rest, strain gauge venous occlusion plethysmography was used to assess limb venous vascular characteristics. Leg venous compliance was significantly decreased after bed rest (pre: 0.048 ± 0.007 ml·100 ml-1·mmHg-1, post: 0.033 ± 0.007 ml·100 ml-1·mmHg-1; P < 0.01), whereas arm compliance did not change. Leg venous flow resistance increased significantly after bed rest (pre: 1.73 ± 1.08 mmHg·ml-1·100 ml·min, post: 3.10 ± 1.00 mmHg·ml-1·100 ml·min; P < 0.05). Maximal lower body negative pressure tolerance, which was expressed as cumulative stress index (pressure·time), decreased in all subjects after bed rest (pre: 932 mmHg·min, post: 747 mmHg·min). The decrease in orthostatic tolerance was not related to changes in leg venous compliance. In conclusion, this study demonstrates that after bed rest, leg venous compliance is reduced and leg venous outflow resistance is enhanced. However, these changes are not related to measures of orthostatic tolerance; therefore, alterations in venous compliance do not to play a major role in orthostatic intolerance after 18 days of head-down tilt bed rest.

Anatomic distribution of pulmonary vascular compliance

1998 ◽  
Vol 84 (1) ◽  
pp. 303-310 ◽  
Author(s):  
Robert G. Presson ◽  
Said H. Audi ◽  
Christopher C. Hanger ◽  
Gerald M. Zenk ◽  
Richard A. Sidner ◽  
...  
Keyword(s):  
Arterial Compliance ◽  
Venous Occlusion ◽  
Longitudinal Distribution ◽  
Steady Flows ◽  
Flow Data ◽  
Venous Compliance ◽  
Vascular Compliance ◽  
Anatomic Distribution ◽  
Flow Changes ◽  
Pressure Changes

Presson, Robert G., Jr., Said H. Audi, Christopher C. Hanger, Gerald M. Zenk, Richard A. Sidner, John H. Linehan, Wiltz W. Wagner, Jr., and Christopher A. Dawson. Anatomic distribution of pulmonary vascular compliance. J. Appl. Physiol. 84(1): 303–310, 1998.—Previously, the pressure changes after arterial and venous occlusion have been used to characterize the longitudinal distribution of pulmonary vascular resistance with respect to vascular compliance using compartmental models. However, the compartments have not been defined anatomically. Using video microscopy of the subpleural microcirculation, we have measured the flow changes in ∼40-μm arterioles and venules after venous, arterial, and double occlusion maneuvers. The quasi-steady flows through these vessels after venous occlusion permitted an estimation of the compliance in three anatomic segments: arteries >40 μm, veins >40 μm, and vessels <40 μm in diameter. We found that ∼65% of the total pulmonary vascular compliance was in vessels <40 μm, presumably mostly capillaries. The transient portions of the pressure and flow data after venous, arterial, and double occlusion were consistent with most of the arterial compliance being upstream from most of the arterial resistance and most of the venous compliance being downstream from most of the venous resistance.

Ultrasound: a reproducible method to measure conduit vein compliance

2005 ◽  
Vol 98 (5) ◽  
pp. 1878-1883 ◽  
Author(s):  
Patricia C. E. de Groot ◽  
Michiel W. P. Bleeker ◽  
Maria T. E. Hopman
Keyword(s):  
Venous Pressure ◽  
Venous Occlusion ◽  
Popliteal Vein ◽  
Venous Compliance ◽  
Ultrasound Technique ◽  
Coefficients Of Variation ◽  
Reproducible Method ◽  
Short And Long Term ◽  
Spinal Cord Injured

Classical venous occlusion plethysmography (VOP) of the leg, often used to assess venous compliance, measures properties of the whole calf, including volume changes at the arterial side and the interstitial fluid accumulation that occurs as a result of the enhanced capillary pressure during venous occlusion. We present an ultrasound technique to measure the compliance of one major conduit vein in the leg. Ultrasound measurements of the popliteal vein were compared with classical VOP measurements, which were performed simultaneously in one subject. Six healthy individuals were measured on three occasions to assess short- and long-term reproducibility of the measurements. Six motor complete spinal cord-injured (SCI) individuals were included to compare venous compliance in subjects with known pathological changes of the venous system with controls. The ultrasound and VOP measurements of venous compliance correlated significantly ( r2 = 0.39, P = 0.001). Ultrasound provides reproducible measurements with short- and long-term coefficients of variation ranging from 10 to 15% for popliteal vein compliance and from 2 to 9% for absolute diameters at the different venous pressure steps. In addition, by using ultrasound, we were able to detect an 80% reduction in the compliance of the popliteal vein in SCI individuals compared with controls ( P < 0.01). In conclusion, ultrasound is a suitable and reproducible method to measure conduit vein compliance and provides the possibility to specifically assess compliance of one vein instead of the whole calf.

Erythropoietin under real and simulated microgravity conditions in humans

1996 ◽  
Vol 81 (2) ◽  
pp. 761-773 ◽  
Author(s):  
H. C. Gunga ◽  
K. Kirsch ◽  
F. Baartz ◽  
A. Maillet ◽  
C. Gharib ◽  
...  
Keyword(s):  
Time Course ◽  
Venous Pressure ◽  
Recovery Period ◽  
Control Period ◽  
Control Level ◽  
Bed Rest ◽  
Control Value ◽  
Real Microgravity ◽  
Microgravity Conditions

The aim of this study was to analyze the time course of erythropoietin (EPO) during Earth-bound microgravity simulations such as bed rest, isolation and confinement (IC), head-down tilt (HDT; -6 degrees), and immersion to evaluate which factors could contribute to alterations in EPO under real microgravity conditions during and after short- (< 10 days) and long-term (> 6 mo) spaceflights. During bed rest (24h), no significant changes in EPO could be observed. Subjects confined in a diving chamber facility for 60 days showed a decrease in EPO. In the recovery period a slight increase was observed, but EPO concentrations did not reach the pre-IC control level. In the control period before HDT, subjects showed normal resting values for EPO, but on day 2 of HDT the EPO concentrations were decreased (P < 0.01). Later the EPO levels remained below the control value and were increased after HDT (P < 0.05). After immersion (24 h) increased EPO concentrations could be determined (P < 0.05). During a short-term spaceflight the astronauts showed in-flight (day 4) decreased and unchanged EPO concentrations. During a long-term spaceflight, 24 h after recovery, the cosmonaut showed slightly elevated EPO concentration, which increased markedly during the following days. It is concluded that 1) HDT (-6 degrees) causes a rapid decrease in EPO in humans, 2) IC per se leads to diminished EPO concentrations, 3) EPO regulation in humans during short- and long-term spaceflights might be different, 4) changes in central blood volume, i.e., central venous pressure, seem to be involved in the modulation of EPO production and release under simulated and real microgravity conditions, and 5) the HDT (-6 degrees) Earth-bound simulation reflects mostly the changes in EPO production and release observed under real microgravity conditions in humans.

scholarly journals Towards a hydrological classification of European soils: preliminary test of its predictive power for the base flow index using river discharge data

2007 ◽  
Vol 11 (4) ◽  
pp. 1501-1513 ◽  
Author(s):  
M. K. Schneider ◽  
F. Brunner ◽  
J. M. Hollis ◽  
C. Stamm
Keyword(s):  
Water Movement ◽  
Base Flow ◽  
Regression Coefficients ◽  
Northern Europe ◽  
Flow Index ◽  
Discharge Data ◽  
Base Flow Index ◽  
The Uk

Abstract. Predicting discharge in ungauged catchments or contaminant movement through soil requires knowledge of the distribution and spatial heterogeneity of hydrological soil properties. Because hydrological soil information is not available at a European scale, we reclassified the Soil Geographical Database of Europe (SGDBE) at 1:1 million in a hydrological manner by adopting the Hydrology Of Soil Types (HOST) system developed in the UK. The HOST classification describes dominant pathways of water movement through soil and was related to the base flow index (BFI) of a catchment (the long-term proportion of base flow on total stream flow). In the original UK study, a linear regression of the coverage of HOST classes in a catchment explained 79% of BFI variability. We found that a hydrological soil classification can be built based on the information present in the SGDBE. The reclassified SGDBE and the regression coefficients from the original UK study were used to predict BFIs for 103 catchments spread throughout Europe. The predicted BFI explained around 65% of the variability in measured BFI in catchments in Northern Europe, but the explained variance decreased from North to South. We therefore estimated new regression coefficients from the European discharge data and found that these were qualitatively similar to the original estimates from the UK. This suggests little variation across Europe in the hydrological effect of particular HOST classes, but decreasing influence of soil on BFI towards Southern Europe. Our preliminary study showed that pedological information is useful for characterising soil hydrology within Europe and the long-term discharge regime of catchments in Northern Europe. Based on these results, we draft a roadmap for a refined hydrological classification of European soils.

scholarly journals Long-term bedrest study and astronaut training

2016 ◽  
Author(s):  
Edwin Mulder ◽  
Alexandra Noppe ◽  
Ulrich Limper
Keyword(s):  
Bed Rest ◽  
Dual Purpose ◽  
Planetary Environments ◽  
Exercise Regimen ◽  
Long Duration ◽  
Astronaut Training ◽  
Health Support ◽  
Art Research ◽  
Induced Changes

In the context of space physiology, research is being conducted to understand the physiological effects from radiation, hypogravity, spaceflight and planetary environments. The goal is to identify new methods to address the unique challenges in medical treatment, human factors, and behavioral health support on future exploration missions. As crew size is small and time is limited during actual missions, space agencies resort to addressing the effects of space travel in analog environments that have features similar to those of spaceflight. Head-down tilt bed rest (HDBR), for instance, is one of the established terrestrial models used to simulate some of the physiological changes experienced during spaceflight under weightless conditions and is therefore considered a valuable testbed to prepare for future long-duration exploration missions. HDBR studies are performed in extremely-well controlled laboratory settings, offering the possibility to test the effects of – what is in essence - physical inactivity and fluid shift. However, HDBR studies have a dual purpose, as they are also invaluable for the development, testing and validation of countermeasures aimed at mitigating microgravity-induced changes to the human body. With respect to the latter, the consensus is that short-term bed rest studies (< 14 days) serve foremost as a first screening of potential promising countermeasures, particularly for the cardiovascular system. Screening of preventative procedures and protocols for the muscular system requires at least mid-term (14 -28 days), whereas studies aiming to validate countermeasures for bone require long-term HDBR studies, in the order of 60-90 days. Hitherto the preferred countermeasure during spaceflight has been physical exercise. The presentation will therefore provide a short overview of the current onboard exercise regimen and will, in light of this, outline the scientific background and aims of the ongoing 60-day HDBR study at the :envihab (from the words ‘Environment’ and ‘Habitat’), the DLR Institute of Aerospace Medicine’s state-of-the-art research facility.

scholarly journals Indices of Increased Decompression Stress Following Long-Term Bed Rest

2018 ◽  
Vol 9 ◽  
Author(s):  
Mikael Gennser ◽  
S. L. Blogg ◽  
Ola Eiken ◽  
Igor B. Mekjavic
Keyword(s):  
Bed Rest ◽  
Decompression Stress

PERIPHERAL CIRCULATORY RESPONSE TO FEEDING IN THE NEWBORN INFANT

PEDIATRICS ◽  
1971 ◽  
Vol 47 (2) ◽  
pp. 378-383
Author(s):  
Alice C. Yao ◽  
C. Göran Wallgren ◽  
Sachchida N. Sinha ◽  
John Lind
Keyword(s):  
Vascular Resistance ◽  
Venous Occlusion ◽  
Term Infants ◽  
Significant Drop ◽  
Circulatory Response ◽  
Control Value ◽  
Limb Perfusion ◽  
Normal Term ◽  
Regional Vascular Resistance ◽  
Umbilical Arterial Catheter

The peripheral circulatory response to feeding was studied in 39 normal term infants, age ranging from 24 hours to 9 days. Blood flow to calf of left leg was measured by the venous occlusion plethysmographic method before and half hourly after feeding for 3 to 3½ hours. Arterial pressure was monitored in nine infants via an umbilical arterial catheter simultaneously and regional vascular resistance to flow in the leg calculated. Changes in pulse rate, and skin and rectal temperatures were also monitored. A significant drop in the calf perfusion averaging 49% of the control value was observed at the 30 minutes postprandial recording. This was due to an increased regional vascular resistance and blood pressure remained unchanged during the time of study. As a rule, a superseding hyperperfusion of the limb overshooting the control value by 40 to 50% occurred 1½ to 3 hours after feeding. This was comparable to the hyperkinetic phase described in adult man and other species after meals. The early postprandial vasoconstriction in the leg seems unique to the newborn. It is suggested that having the early circulatory demand provoked by feeding is relatively bigger in the newborn than in the adult and is met partly at the expense of lower limb perfusion.

scholarly journals Long-term hydrological changes after various river regulation measures: are we responsible for flow extremes?

2019 ◽  
Vol 50 (2) ◽  
pp. 417-430 ◽  
Author(s):  
Tímea Kiss ◽  
Károly Fiala ◽  
György Sipos ◽  
Gábor Szatmári
Keyword(s):  
Human Impacts ◽  
Morphological Changes ◽  
River Regulation ◽  
Mass Movements ◽  
Channel Adjustment ◽  
Flood Level ◽  
Flow Changes ◽  
Tisza River ◽  
Natural Channel

Abstract Engineering works have affected the morphology of rivers (e.g., by cut-offs, artificial levees, revetments, and reservoir and dam constructions). These human impacts also have hydrological impacts, as they alter the natural channel geometry, affect the carrying capacity of the channel and confine the floodplains. The goals of the present paper are to analyse flow changes for the Tisza River (in Hungary) with its highly regulated channel using a long (141 y) daily hydrologic dataset and to evaluate the engineering works from the point of hydrological and morphological equilibrium. Since the late 19th century, the flood level along the Lower Tisza River has increased by 216 cm; further, since 1998, flood levels increased by over 80 cm without an increase in discharge. In addition, river stages for low flows have decreased, and the water slope has decreased. These changes are likely connected to morphological changes in the channel (e.g., incision, narrowing, disappearance of point bars, intensifying mass movements), which have been driven by the complex response to human impacts. While the channel could adjust itself to convey larger floods after the cut-offs, the revetments impede the channel adjustment and contribute to the hydrological and morphological disequilibrium state along the Tisza River.

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