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)

Alveolar pressure in fluid-filled occluded lung segments during permeability edema

1983 ◽  
Vol 55 (4) ◽  
pp. 1098-1102
Author(s):  
J. P. Kohler ◽  
C. L. Rice ◽  
G. S. Moss ◽  
J. P. Szidon
Keyword(s):  
Oleic Acid ◽  
Hydrostatic Pressure ◽  
Pulmonary Edema ◽  
Intravenous Injection ◽  
Interstitial Fluid ◽  
Fluid Pressure ◽  
Base Line ◽  
Interstitial Pressure ◽  
Alveolar Pressure ◽  
Permeability Pulmonary Edema

In a model of increased hydrostatic pressure pulmonary edema Parker et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 267-276, 1978) demonstrated that alveolar pressure in occluded fluid-filled lung segments was determined primarily by interstitial fluid pressure. Alveolar pressure was subatmospheric at base line and rose with time as hydrostatic pressure was increased and pulmonary edema developed. To further test the hypothesis that fluid-filled alveolar pressure is determined by interstitial pressure we produced permeability pulmonary edema-constant hydrostatic pressure. After intravenous injection of oleic acid in dogs (0.01 mg/kg) the alveolar pressure rose from -6.85 +/- 0.8 to +4.60 +/- 2.28 Torr (P less than 0.001) after 1 h and +6.68 +/- 2.67 Torr (P less than 0.01) after 3 h. This rise in alveolar fluid pressure coincided with the onset of pulmonary edema. Our experiments demonstrate that during permeability pulmonary edema with constant capillary hydrostatic pressures, as with hemodynamic edema, alveolar pressure of fluid-filled segments seems to be determined by interstitial pressures.

Tissue pressure and plasma oncotic pressure during exercise

1984 ◽  
Vol 56 (1) ◽  
pp. 102-108 ◽  
Author(s):  
V. Mohsenin ◽  
R. R. Gonzalez
Keyword(s):  
Osmotic Pressure ◽  
Plasma Volume ◽  
Interstitial Fluid ◽  
Vastus Lateralis ◽  
Fluid Pressure ◽  
Colloid Osmotic Pressure ◽  
Interstitial Fluid Pressure ◽  
Plasma Sodium ◽  
Vastus Lateralis Muscle ◽  
Base Line

Six healthy male subjects exercised on a cycle ergometer for 3 min for assessment of forces involved in transvascular fluid shift during intense exercise. The work load was at 105% of peak O2 uptake of the subjects. This caused a 17.2 +/- 1.2% reduction in plasma volume. The plasma volume loss was associated with an increase in plasma sodium, from 142.6 +/- 0.5 to 148.1 +/- 1.0 meq X 1(-1) (P less than 0.005); chloride, from 101.8 +/- 0.6 to 104.6 +/- 0.9 meq X 1(-1) (P less than 0.005); lactate, from 1.4 +/- 0.2 to 14.0 +/- 1.5 meq X 1(-1) (P less than 0.005); and osmolality, from 283 +/- 2 to 299 +/- 3 mosmol X kg-1 H2O (P less than 0.005) within 2 min after cessation of exercise. Plasma protein increased from 7.0 +/- 0.2 to 8.1 +/- 0.3 g X dl-1 (P less than 0.005), and plasma colloid osmotic pressure from 25.1 +/- 0.6 to 30.6 +/- 1.4 mmHg (P less than 0.005) after exercise. Interstitial fluid pressure in the exercising vastus lateralis muscle increased from a base-line value (SE) of -1.0 +/- 0.9 to + 1.5 +/- 1.1 cmH2O, 14 min after the end of exercise (P less than 0.05). Interstitial fluid pressure of the triceps brachii (inactive) did not change significantly after exercise. Our data suggest that increased transvascular colloid osmotic pressure and elevation of interstitial fluid pressure become increasingly important in preventing loss of plasma volume during maximal exercise.

Comparison of methods for measurement of interstitial fluid pressure in cat skin/subcutis and muscle

1985 ◽  
Vol 249 (5) ◽  
pp. H929-H944 ◽  
Author(s):  
H. Wiig
Keyword(s):  
Skeletal Muscle ◽  
Peritoneal Dialysis ◽  
Steady State ◽  
Interstitial Fluid ◽  
Fluid Pressure ◽  
Interstitial Fluid Pressure ◽  
Comparison Of Methods ◽  
Porous Polyethylene ◽  
Transient Rise ◽  
Pressure Changes

Interstitial fluid pressure (IFP) in cats was measured with four techniques, i.e., hollow perforated and porous polyethylene capsules, wick in needle (WIN), and micropipettes. During control conditions, skin IFP of -1.5 +/- 0.4 (SD) mmHg (n = 53) was obtained with micropipettes, whereas pressures recorded in subcutis with perforated and porous capsules were -1.6 +/- 0.9 (n = 26) and -1.6 +/- 0.8 mmHg (n = 13), respectively. These were all significantly different from the -1.2 +/- 0.5 mmHg (n = 50) obtained in subcutis with WIN. In skeletal muscle, control IFP of -0.5, -0.5, and -1.1 mmHg was measured with micropipettes, WIN, and porous capsules, respectively. During peritoneal dialysis skin and muscle IFP recorded with micropipettes and WIN was reduced by 3-3.5 mmHg, whereas pressure in porous and perforated capsules fell by 7 and 10 mmHg, respectively. Intravenous Ringer infusion caused a marked transient rise in capsular pressures, not reflected by micropipettes and WIN, but similar pressures were obtained 210 min after infusion. In conclusion, all techniques reflect true IFP under steady-state conditions. Both capsules apparently act like osmometers in acute overhydration or dehydration and are, in addition, sensitive to pressure changes in local veins and are therefore not suitable for measurement of changes in IFP that take place in less than a few hours.

Measurement of subcutaneous tissue fluid pressure using a skin-cup method

1985 ◽  
Vol 58 (5) ◽  
pp. 1528-1535 ◽  
Author(s):  
T. H. Adair ◽  
A. C. Guyton
Keyword(s):  
Steady State ◽  
Subcutaneous Tissue ◽  
Fluid Pressure ◽  
Recording System ◽  
Servo Control ◽  
Free Fluid ◽  
Tissue Fluid ◽  
Dynamic Changes ◽  
Servo Control System ◽  
Small Needle

We developed a new method for measuring tissue fluid pressure in subcutaneous tissue. Porous Teflon cylinders were permanently implanted subcutaneously into the inguinal area of 10 dogs, and after several weeks a skin concavity formed in the center of each of the cylinders. A small needle attached to a recording system was inserted into the free tissue fluid lining the concavity, and the tissue fluid pressure averaged -8.8 +/- 2.7 (SD) mmHg. Next, a hollow Plexiglas cup was placed over the concavity and glued to the skin. The air pressure in the skin cup was continually adjusted (using an electromechanical servo-control system) to pull the skin upward and to hold it perfectly flat across the upper ridge of the Teflon cylinder. The simultaneously recorded needle and cup pressures averaged -9.1 +/- 2.4 and -8.6 +/- 2.6 mmHg, respectively, during steady-state conditions with the skin in a flat position. Both pressures also responded appropriately to dynamic changes in tissue fluid pressure caused by increasing and decreasing the volume of the free tissue fluid. Because the skin was flat, the equivalences of pressures above and below the skin is consistent with the hypothesis that the skin was not tethered significantly to the underlying tissues and that cup pressure accurately estimates the tissue free fluid pressure.

Interstitial fluid pressure of ileum measured from chronically implanted polyethylene capsules

1989 ◽  
Vol 257 (1) ◽  
pp. H62-H69 ◽  
Author(s):  
N. A. Mortillaro ◽  
A. E. Taylor
Keyword(s):  
Steady State ◽  
Interstitial Fluid ◽  
Portal Pressure ◽  
Fluid Pressure ◽  
Arterial Occlusion ◽  
Interstitial Fluid Pressure ◽  
Venous Outflow ◽  
Fluid Filtration ◽  
Tissue Hydration ◽  
Venous Outflow Pressure

Steady-state fluid pressure measurements were obtained from polyethylene capsules chronically implanted in the walls of cat ileum. Measurements were performed while ileal venous outflow pressure was maintained at 0, 10, 20, or 30 mmHg. The resulting mean steady-state capsule pressure ranged from -0.56 to 7.3 mmHg over the range of imposed venous outflow pressures. The data provide evidence that at an ileal venous outflow pressure in the range of 10 mmHg, comparable to a normal portal pressure, interstitial fluid pressure is positive, increasing as tissue hydration increases, and is a significant contributing force opposing increases in the transcapillary filtration force. Additionally, the qualitative response of implanted capsules to close intra-arterial infusion of normal saline (transcapillary filtration), Dextran 40 (transcapillary absorption), and histamine (transcapillary filtration-permeability changes), and during and after an arterial occlusion of 60-s duration (transcapillary absorption-filtration) were obtained. The results demonstrate that the implanted capsules appropriately track changes in interstitial fluid pressure when the state of tissue hydration is altered by an induced net transcapillary fluid filtration or absorption. Finally, total protein concentration of capsule fluid was not significantly different from lymph fluid derived from a lymphatic vessel draining the ileal segment.

Control of interstitial fluid pressure: Role of [beta ]-integrins

2001 ◽  
Vol 21 (3) ◽  
pp. 222-230 ◽  
Author(s):  
Rolf K. Reed ◽  
Ansgar Berg ◽  
Eli-Anne B. Gjerde ◽  
Kristofer Rubin
Keyword(s):  
Interstitial Fluid ◽  
Fluid Pressure ◽  
Interstitial Fluid Pressure

Approximate analysis of the containment of contaminated sites prior to remediation

2000 ◽  
Vol 42 (1-2) ◽  
pp. 319-324 ◽  
Author(s):  
H. Rubin ◽  
A. Rabideau
Keyword(s):  
Steady State ◽  
Peclet Number ◽  
Dimensionless Parameter ◽  
Contaminated Sites ◽  
Unsteady State ◽  
Péclet Number ◽  
Vertical Barrier ◽  
Time Period ◽  
Barrier Performance ◽  
Vertical Barriers

This study presents an approximate analytical model, which can be useful for the prediction and requirement of vertical barrier efficiencies. A previous study by the authors has indicated that a single dimensionless parameter determines the performance of a vertical barrier. This parameter is termed the barrier Peclet number. The evaluation of barrier performance concerns operation under steady state conditions, as well as estimates of unsteady state conditions and calculation of the time period requires arriving at steady state conditions. This study refers to high values of the barrier Peclet number. The modeling approach refers to the development of several types of boundary layers. Comparisons were made between simulation results of the present study and some analytical and numerical results. These comparisons indicate that the models developed in this study could be useful in the design and prediction of the performance of vertical barriers operating under conditions of high values of the barrier Peclet number.

Dynamics of Interstitial Fluid Pressure in Extracellular Matrix Hydrogels in Microfluidic Devices

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Joe Tien ◽  
Le Li ◽  
Ozgur Ozsun ◽  
Kamil L. Ekinci
Keyword(s):  
Extracellular Matrix ◽  
Pressure Distribution ◽  
Interstitial Fluid ◽  
Scaling Laws ◽  
Fluid Pressure ◽  
Interstitial Fluid Pressure ◽  
External Loading ◽  
Interstitial Pressure ◽  
Time Resolved ◽  
Long Time

In order to understand how interstitial fluid pressure and flow affect cell behavior, many studies use microfluidic approaches to apply externally controlled pressures to the boundary of a cell-containing gel. It is generally assumed that the resulting interstitial pressure distribution quickly reaches a steady-state, but this assumption has not been rigorously tested. Here, we demonstrate experimentally and computationally that the interstitial fluid pressure within an extracellular matrix gel in a microfluidic device can, in some cases, react with a long time delay to external loading. Remarkably, the source of this delay is the slight (∼100 nm in the cases examined here) distension of the walls of the device under pressure. Finite-element models show that the dynamics of interstitial pressure can be described as an instantaneous jump, followed by axial and transverse diffusion, until the steady pressure distribution is reached. The dynamics follow scaling laws that enable estimation of a gel's poroelastic constants from time-resolved measurements of interstitial fluid pressure.

Modelling And Simulation of Topical Drug Diffusion in The Dermal Layer of Human Body

2021 ◽  
Vol 86 (2) ◽  
pp. 39-49
Author(s):  
Sudi Mungkasi
Keyword(s):  
Steady State ◽  
Human Body ◽  
Diffusion Problem ◽  
State Condition ◽  
Unsteady State ◽  
Steady State Condition ◽  
Drug Diffusion ◽  
Dermal Layer ◽  
Drug Concentrations ◽  
Proposed Model

We consider the problem of drug diffusion in the dermal layer of human body. Two existing mathematical models of the drug diffusion problem are recalled. We obtain that the existing models lead to inconsistent equations for the steady state condition. We also obtain that solutions to the existing models are unrealistic for some cases of the unsteady state condition, because negative drug concentrations occur due to the inappropriate assumption of the model. Therefore, in this paper, we propose a modified mathematical model, so that the model is consistent, and the solution is nonnegative for both steady and unsteady state conditions of the drug diffusion problem in the dermal layer of human body. For the steady state condition, the exact solution to the proposed model is given. For unsteady state condition, we use a finite difference method for solving the models numerically, where the discretisation is centred in space and forward in time. Simulation results confirm that our proposed model and method preserve the non-negativity of the solution to the problem, so the solution is more realistic than that of the old model.

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