A theoretical approach to analyze pressure equilibria in the interstitium

1990 ◽  
Vol 258 (3) ◽  
pp. F705-F710 ◽  
Author(s):  
M. Gilanyi ◽  
A. G. Kovach
Keyword(s):  
Osmotic Pressure ◽  
Fluid Pressure ◽  
Quantitative Relationship ◽  
Fluid Phase ◽  
Free Fluid ◽  
Transient Effects ◽  
Measuring Devices ◽  
Pressure Term ◽  
Gel Phase ◽  
Osmotic Pressure Difference

Inherent problems concerning the interstitial fluid pressure (IFP) are reinvestigated on theoretical grounds. Analyzing the thermodynamic and mechanical equilibria in the interstitium, it is concluded that IFP includes a pressure term originating from the elastic forces and an osmotic pressure term. A quantitative relationship is established between the IFP and all of the parameters responsible for the changes in the recorded pressure. The theoretical results suggest that, under control conditions, 1) there are no permanently existing free fluid spaces, 2) the gel pressure is atmospheric, and 3) the fluid equilibration techniques measure an osmotic pressure difference between the gel phase and the fluid phase created artificially by any of the pressure measuring devices. The pressure response during acute volume changes is attributed to the changes in the osmotic pressure term, gel volume, and elasticity. Volume and elasticity changes are reflected in the recorded IFP as promptly developing and permanent effects; on the other hand, osmotic processes result in slowly developing and transient effects. The volume-pressure relationship is also analyzed.

Evaluation of the Starling Fluid Flux Equation

Physiology ◽  
1987 ◽  
Vol 2 (2) ◽  
pp. 48-52 ◽  
Author(s):  
AE Taylor ◽  
MI Townsley
Keyword(s):  
Osmotic Pressure ◽  
Pressure Difference ◽  
Fluid Pressure ◽  
Colloid Osmotic Pressure ◽  
Lymph Flow ◽  
Tissue Fluid ◽  
Fluid Flux ◽  
Dynamic Factors ◽  
Osmotic Pressure Difference ◽  
Absorption Theory

It is commonly thought that fluid is filtered in the arterial and is absorbed in the venous end of the capillary, cuased by the considerable hydrostatic pressure difference between the arterial and the venous end, while the transcapillary colloid osmotic pressure difference remains nearly constant. We now know that extravascular forces, i.e., tissue fluid pressure, tissue colloid osmotic pressure, and lymph flow, are dynamic factors that change to oppose transcapillary fluid movement. Therefore, the filtration-absorption theory will apply only transiently until the tissue forces readjust.

scholarly journals Using mineral equilibria to estimate H2O activities in peridotites from the Western Gneiss Region of Norway

2017 ◽  
Vol 102 (5) ◽  
pp. 1021-1036 ◽  
Author(s):  
Patricia Kang ◽  
William M. Lamb ◽  
Martyn Drury
Keyword(s):  
Physical Properties ◽  
Fluid Pressure ◽  
Fluid Phase ◽  
Stability Field ◽  
Lithostatic Pressure ◽  
Free Fluid ◽  
Western Gneiss Region ◽  
Mineral Equilibria ◽  
Earth’S Mantle ◽  
Absent Condition

Abstract The Earth’s mantle is an important reservoir of H2O, and even a small amount of H2O has a significant influence on the physical properties of mantle rocks. Estimating the amount of H2O in rocks from the Earth’s mantle would, therefore, provide some insights into the physical properties of this volumetrically dominant portion of the Earth. The goal of this study is to use mineral equilibria to determine the activities of H2O (aH2O) in orogenic mantle peridotites from the Western Gneiss Region of Norway. An amphibole dehydration reaction yielded values of aH2O ranging from 0.1 to 0.4 for these samples. Values of fO2 of approximately 1 to 2 log units below the FMQ oxygen buffer were estimated from a fO2-buffering reaction between olivine, orthopyroxene, and spinel for these same samples. These results demonstrate that the presence of amphibole in the mantle does not require elevated values of aH2O (i.e., aH2O≈1) nor relatively oxidizing values of fO2 (i.e., >FMQ). It is possible to estimate a minimum value of aH2O by characterizing fluid speciation in C-O-H system for a given value of oxygen fugacity (fO2). Our results show that the estimates of aH2O obtained from the amphibole dehydration equilibrium are significantly lower than values of aH2O estimated from this combination of fO2 and C-O-H calculations. This suggests that fluid pressure (Pfluid) is less than lithostatic pressure (Plith) and, for metamorphic rocks, implies the absence of a free fluid phase. Fluid absent condition could be generated by amphibole growth during exhumation. If small amounts of H2O were added to these rocks, the formation of amphibole could yield low values of aH2O by consuming all available H2O. On the other hand, if the nominally anhydrous minerals (NAMs) contained significant H2O at conditions outside of the stability field of amphibole they might have served as a reservoir of H2O. In this case, NAMs could supply the OH necessary for amphibole growth once retrograde P-T conditions were consistent with amphibole stability. Thus, amphibole growth may effectively dehydrate coexisting NAMs and enhance the strength of rocks as long as the NAMs controlled the rheology of the rock.

Transcapillary Starling pressures in the fetus, newborn, adult, and pregnant adult

1981 ◽  
Vol 240 (6) ◽  
pp. H843-H847 ◽  
Author(s):  
R. A. Brace ◽  
J. L. Christian
Keyword(s):  
Guinea Pig ◽  
Osmotic Pressure ◽  
Species Differences ◽  
Subcutaneous Tissue ◽  
Fluid Pressure ◽  
Fluid Distribution ◽  
Free Fluid ◽  
Interstitial Free ◽  
Major Species ◽  
Guinea Pig Fetus

We used the method of membrane osmometry to determine capillary pressure (Pc), plasma protein osmotic pressure (IIp), interstitial protein osmotic pressure (IIif), and interstitial free fluid pressure (Pif) in subcutaneous tissue. These pressures were measured in the sheep and guinea pig fetus, newborn, adult, and pregnant adult. Although there were some similarities, we found major species differences. 1) IIp was a minimum in the fetus and gradually increased to a maximum with adulthood in the guinea pig, whereas IIp attained adult values in the newborn lamb. 2) IIp and Pc did not change with pregnancy in sheep, but, in the guinea pig, IIp and Pc decreased by approximately 30% during pregnancy. 3) The maximum and minimum IIif occurred in the fetal and adult guinea pig, respectively, whereas this was reversed in the sheep. 4) IIif decreased with pregnancy in the guinea pig but not in the sheep. 5) The minimum Pif was found in the newborn of both species. These data suggest that the forces that determine the intravascular-interstitial fluid distribution are different in the fetus, newborn, and adult and also vary among species.

A model of unsteady-state transvascular fluid and protein transport in the lung

1984 ◽  
Vol 56 (5) ◽  
pp. 1389-1402 ◽  
Author(s):  
R. J. Roselli ◽  
R. E. Parker ◽  
T. R. Harris
Keyword(s):  
Steady State ◽  
Interstitial Fluid ◽  
Transport Theory ◽  
Fluid Pressure ◽  
Water Volume ◽  
Free Fluid ◽  
Base Line ◽  
Unsteady State ◽  
Total Change ◽  
Organ Systems

Models of steady-state fluid and solute transport in the microcirculation are used primarily to characterize filtration and permeability properties of the transport barrier. Important transient relationships, such as the rate of fluid accumulation in the tissue, cannot be predicted with steady-state models. In this paper we present three simple models of unsteady-state fluid and protein exchange between blood plasma and interstitial fluid. The first treats the interstitium as a homogeneous well-mixed compliant compartment, the second includes an interstitial gel, and the third allows for both gel and free fluid in the interstitium. Because we are primarily interested in lung transvascular exchange we used the multiple-pore model and pore sizes described by Harris and Roselli (J. Appl. Physiol.: Respirat . Environ. Exercise Physiol. 50: 1–14, 1981) to characterize the microvascular barrier. However, the unsteady-state transport theory presented here should apply to other organ systems and can be used with different conceptual models of the blood-lymph barrier. For a step increase in microvascular pressure we found good agreement between theoretical and experimental lymph flow and lymph concentrations in the sheep lung when the following parameter ranges were used: base-line interstitial volume, 150–190 ml; interstitial compliance, 7–10 ml/Torr; initial interstitial fluid pressure, -1 Torr; pressure in initial lymphatics, -5 to -6 Torr; and conductivity of the interstitium and lymphatic barrier, 4.25 X 10(-4) ml X s-1 X Torr-1. Based on these values the model predicts 50% of the total change in interstitial water volume occurs in the first 45 min after a step change in microvascular pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of hydrostatic pressure gradients on regulation of plasma volume after exercise

1998 ◽  
Vol 85 (2) ◽  
pp. 667-675 ◽  
Author(s):  
Gary W. Mack ◽  
Roger Yang ◽  
Alan R. Hargens ◽  
Kei Nagashima ◽  
Andrew Haskell
Keyword(s):  
Hydrostatic Pressure ◽  
Osmotic Pressure ◽  
Plasma Volume ◽  
Fluid Pressure ◽  
Colloid Osmotic Pressure ◽  
Upright Position ◽  
Upright Posture ◽  
Immediate Recovery ◽  
Before And After ◽  
The Impact

The impact of posture on the immediate recovery of intravascular fluid and protein after intense exercise was determined in 14 volunteers. Forces which govern fluid and protein movement in muscle interstitial fluid pressure (PISF), interstitial colloid osmotic pressure (COPi), and plasma colloid osmotic pressure (COPp) were measured before and after exercise in the supine or upright position. During exercise, plasma volume (PV) decreased by 5.7 ± 0.7 and 7.0 ± 0.5 ml/kg body weight in the supine and upright posture, respectively. During recovery, PV returned to its baseline value within 30 min regardless of posture. PV fell below this level by 60 and 120 min in the supine and upright posture, respectively ( P < 0.05). Maintenance of PV in the upright position was associated with a decrease in systolic blood pressure, an increase in COPp (from 25 ± 1 to 27 ± 1 mmHg; P < 0.05), and an increase in PISF (from 5 ± 1 to 6 ± 2 mmHg), whereas COPi was unchanged. Increased PISFindicates that the hydrostatic pressure gradient favors fluid movement into the vascular space. However, retention of the recaptured fluid in the plasma is promoted only in the upright posture because of increased COPp.

Transcapillary Starling forces using membrane osmometry

1980 ◽  
Vol 238 (6) ◽  
pp. H886-H888
Author(s):  
J. L. Christian ◽  
R. A. Brace
Keyword(s):  
Osmotic Pressure ◽  
Interstitial Fluid ◽  
Subcutaneous Tissue ◽  
Fluid Pressure ◽  
Colloid Osmotic Pressure ◽  
Interstitial Fluid Pressure ◽  
Tissue Samples ◽  
Small Pore ◽  
The Difference ◽  
Good Agreement

Membrane osmometry was used to estimate the four transcapillary Starling pressures in subcutaneous tissue of rats, guinea pigs, and dogs. Isolated subcutaneous tissue samples were either placed on a large-pore or small-pore osmometer that measured the interstitial fluid pressure (Pif) and the difference between the interstitial fluid pressure and the interstitial protein osmotic pressure (Pif-pi if), respectively. The colloid osmotic pressure of the interstitial fluid (pi if) was obtained from the difference in these two pressures. A plasma sample placed on the small-pore osmometer yielded the colloid osmotic pressure of the plasma proteins (pi c). Finally the capillary pressure (Pc) was calculated from the three other Starling forces. In the rat, guinea pig, and dog, respectively, the estimated Starling forces were as follows: Pif -2.2, -2.1, and -4.8 mmHg; pi if, 7.3, 4.8, and 4.4 mmHg; pi c, 21.3, 19.5, and 19.2 mmHg; and Pc, 11.8, 12.6, and 10.0 mmHg. A comparison with data obtained in other studies using different methods shows good agreement and strongly supports membrane osmometry as a method for measuring the Starling pressures in subcutaneous tissue.

Physiological effects of pH changes on colloid osmotic pressures

1985 ◽  
Vol 248 (6) ◽  
pp. H890-H893 ◽  
Author(s):  
B. R. Will ◽  
R. A. Brace
Keyword(s):  
Osmotic Pressure ◽  
Interstitial Fluid ◽  
Ph Dependence ◽  
Fluid Pressure ◽  
Human Albumin ◽  
Interstitial Fluid Pressure ◽  
Fluid Distribution ◽  
Ground Substance ◽  
Physiological Range ◽  
Umbilical Cords

Our purpose was to explore the effects of variations in pH, particularly in the physiological range, on the colloid osmotic pressure (COP) of the body's fluids. Theoretically, changing pH would alter the electrical charge density on plasma proteins and the interstitial ground substance, thereby altering plasma and interstitial protein osmotic pressure as well as interstitial fluid pressure. We found that the COP of human plasma, human albumin, bovine albumin, and Wharton's jelly from human umbilical cords increased linearly as pH increased over the range of 6.0–8.0. COP of plasma and the albumins all displayed essentially the same sensitivity to pH. At equal concentrations, hyaluronate in umbilical cords was approximately 16 times more sensitive to pH than was plasma. Dextran 70 displayed no COP dependency on pH. For plasma, the albumins, and hyaluronate the pH dependence of COP on pH also decreased linearly with concentration (C in g/dl). For plasma and the albumins over the physiological range of pH, COP = COPpH 7.4 [1.00 + 0.01C (pH -7.40)] at 37 degrees C. The data suggest that, relative to the normal net transcapillary pressure gradient, physiological variations in pH affect plasma COP as well as interstitial fluid pressure and thus may play a significant role in regulating the body's fluid distribution.

Branchiostoma lanceolatum – A Freshwater Reject?

1979 ◽  
Vol 59 (1) ◽  
pp. 61-67 ◽  
Author(s):  
John Binyon
Keyword(s):  
Osmotic Pressure ◽  
Functional Ability ◽  
Pressure Difference ◽  
Great Difficulty ◽  
Body Fluids ◽  
Branchiostoma Lanceolatum ◽  
Osmotic Pressure Difference

The ultrastructure and dimensions of the solenocytes of Branchiostoma lanceolatum are reviewed briefly. The functional ability of these units is calculated upon theoretical grounds in a manner similar to that applied to flame cells. Their more delicate construction would suggest that Branchiostoma would have great difficulty in maintaining any significant osmotic pressure difference between the medium and its body fluids.

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