Effect of increased neck vein pressure on intestinal lymphatic pressure in awake sheep

1992 ◽  
Vol 262 (5) ◽  
pp. R892-R894 ◽  
Author(s):  
R. E. Drake ◽  
R. D. Abbott
Keyword(s):  
Thoracic Duct ◽  
Lymphatic Vessels ◽  
Ringer Solution ◽  
Lymph Flow ◽  
The Other ◽  
Flow Rates ◽  
Intestinal Lymph ◽  
Other Hand ◽  
Intestinal Lymphatics ◽  
Increased Pressure

Lymphatic vessels from the intestines drain into the thoracic duct, and the thoracic duct empties into veins in the neck. Thus increases in neck vein pressure (PNV) might slow intestinal lymph flow, provided the increased pressure is reflected upstream through the lymphatic vessels. To test the effect of increases in PNV on lymphatic pressure, we cannulated intestinal lymphatics in the direction of flow in six sheep. After the sheep recovered from surgery, we measured the pressure in the lymphatics (Px) as we increased PNV in steps. Px increased only slightly (but significantly) from 7.4 +/- 2.0 to 11.4 +/- 5.2 (SD) cmH2O when we increased PNV from baseline (0.8 +/- 2.4 cmH2O) to 37.4 +/- 4.1 cmH2O. However, when we simulated an increased lymph flow by infusing Ringer solution into the lymphatics at 1,000 microliters/min, Px increased to 24.6 +/- 7.0 cmH2O at PNV equal to 37.1 +/- 5.3 cmH2O. These results indicate that, at normal lymph flow rates, increases in neck vein pressure cause only small increases in intestinal lymphatic pressure. On the other hand, when lymph flow is elevated, increases in neck vein pressure may substantially increase lymphatic pressure and thus slow intestinal lymph flow.

Effect of outflow pressure on intestinal lymph flow in unanesthetized sheep

1991 ◽  
Vol 260 (4) ◽  
pp. R668-R671 ◽  
Author(s):  
R. E. Drake ◽  
J. C. Gabel
Keyword(s):  
Stroke Volume ◽  
Flow Rate ◽  
Venous Pressure ◽  
Lymphatic Vessels ◽  
Lymph Flow ◽  
Pump Failure ◽  
Intestinal Lymph ◽  
Intestinal Lymphatics ◽  
Lymphatic Pumping ◽  
The Relationship

Lymphatic vessels are important in removing excess fluid from the intestines and preventing intestinal edema. In this study we used the relationship between intestinal lymph flow rate (QL) and lymphatic outflow pressure (PO) to analyze the flow from intestinal lymphatics in unanesthetized sheep. We cannulated intestinal lymphatic vessels in six anesthetized sheep. One to 3 days after the surgery, we measured QL as we increased PO in steps. We found no QL decrease until PO greater than 15 cmH2O, but QL decreased significantly for PO greater than 15 cmH2O and was decreased to zero at PO = 34 +/- 13 (SD) cmH2O. In three experiments, we used the pressure pulses generated by the active lymphatic pump to estimate the pump stroke volume and frequency. These data indicate that increases in lymphatic pumping prevented a QL decreased for PO less than 15 cmH2O and the QL decrease for PO greater than 15 cmH2O was associated with lymphatic pump failure. When we increased portal venous pressure from baseline (10.1 +/- 4.1 cmH2O) to 24.3 +/- 6.2 cmH2O, lymph flow increased, but it was much more sensitive to outflow pressure. These results are important because they indicate that the ability of the lymphatics to remove fluid from edematous intestines may be compromised by small increases in lymphatic outflow pressure.

Thoracic duct lymph flow in pregnant sheep and response to blood volume expansion

1986 ◽  
Vol 250 (6) ◽  
pp. R1095-R1098 ◽  
Author(s):  
G. Valenzuela ◽  
L. L. Woods ◽  
R. A. Brace
Keyword(s):  
Blood Volume ◽  
Flow Rate ◽  
Thoracic Duct ◽  
Ringer Solution ◽  
Lymph Flow ◽  
Thoracic Duct Lymph ◽  
Volume Loading ◽  
Flow Rates ◽  
Pregnant Sheep ◽  
Duct Lymph

Left thoracic duct lymph flow rate averaged 0.077 +/- 0.003 (SD) and 0.078 +/- 0.003 ml X min-1 X kg-1 in near-term pregnant and nonpregnant sheep (P greater than 0.5). Lymph and plasma protein concentrations were unaltered in the pregnant compared with the nonpregnant animals. The thoracic duct lymph flow responses to three serial intravenous infusions of lactated Ringer solution were essentially the same in the pregnant and nonpregnant animals. Blood volume and vascular pressure changes during and after volume loading were essentially the same in both groups. In addition, terbutaline administration after volume loading caused no change in thoracic duct lymph flow rates. Thus the present study suggests that basal lymph flow rates, lymphatic function, and vascular as well as interstitial compliances are largely unaltered late in pregnancy in the sheep. In addition, beta-mimetic stimulation with terbutaline does not appear to suppress lymph flow rate.

Preliminary Investigation on the Effect of the Modification of the Sweep Angle at the Blade Tip of Forward Swept Axial Fans

2017 ◽  
Author(s):  
Massimo Masi ◽  
Andrea Lazzaretto
Keyword(s):  
Preliminary Investigation ◽  
Suction Side ◽  
The Other ◽  
Axial Fan ◽  
Sweep Angle ◽  
End Effects ◽  
Flow Rates ◽  
Stall Margin ◽  
Other Hand ◽  
Blade Tip

The flow path close to the suction side of fan rotor blades mostly affects the overall drag of the blading. The blade lift is affected as well because of the separation of the low energy boundary layer that drives the blade into stall at low fan flow rates. Forward sweep allows to position the airfoil sections of blades featuring a positive circulation gradient along the span so that they “accompany” the near-wall flow trajectories at the blade suction side. So, rotor efficiency and stall margin of the fan can be improved. On the other hand, blade end effects play a relevant role in high hub-to-tip and low aspect ratio rotors and may compromise the effectiveness of forward sweep. Nevertheless, some authors in the literature stated the beneficial contribution of changing the sweep angle at the ends of the blade both at design and off-design conditions. The paper studies the end effects on constant-swirl design rotors by means of CFD simulations focusing on the distribution of blade sweep in the near-tip region. In particular, the performance and efficiency calculated for a forward swept tube-axial fan featuring a hub-to-tip ratio equal to 0.4 are compared with those estimated for the corresponding unswept fan at equal duty point. Several modifications of the sweep distribution in the blade tip region are considered in the swept fan to quantify their effect on performance, efficiency and stall margin. Results show that the addition of up to 6 degrees of local forward sweep at the blade tip to the unswept blading does not affect fan pressure at design operation. On the other hand, this local increase of the sweep angle allows for a very notable increase of the peak pressure and efficiency at flow rates close to stall inception.

Lymph flow in sheep with rapid cardiac ventricular pacing

1997 ◽  
Vol 272 (5) ◽  
pp. R1595-R1598 ◽  
Author(s):  
R. E. Drake ◽  
S. Dhother ◽  
R. A. Teague ◽  
J. C. Gabel
Keyword(s):  
Heart Failure ◽  
Flow Rate ◽  
Mediastinal Lymph Node ◽  
Venous Pressure ◽  
Lymphatic Vessels ◽  
Lymph Flow ◽  
Ventricular Pacing ◽  
Fluid Filtration ◽  
Flow Rates ◽  
Lymphatic Flow

Increases in systemic venous pressure (Pv) associated with heart failure cause an increase in microvascular fluid filtration into the tissue spaces. By removing this excess filtrate from the tissues, lymphatic vessels help to prevent edema. However, the lymphatics drain into systemic veins and an increase in Pv may interfere with lymphatic flow. To test this, we cannulated caudal mediastinal node efferent lymphatics in sheep. We used rapid cardiac ventricular pacing (240-275 beats/min) to cause heart failure for 4-7 days. Each day we determined the lymph flow rate two ways. First, we adjusted the lymph cannula height so that the pressure at the outflow end of the lymphatic was zero. After we determined the lymph flow with zero outflow pressure, we raised the cannula so that outflow pressure was equal to the actual venous pressure. We quantitated the effect of venous pressure on lymph flow rate by comparing the flow rate with outflow pressure = Pv to the flow rate with zero out low pressure. At baseline, Pv = 5.0 +/- 2.5 (SD) cmH2O and we found no difference in the two lymph flow rates. Pacing caused Pv and both lymph flow rates to increase significantly. However for Pv < 15 cmH2O, we found little difference in the two lymph flow rates. Thus increases in Pv to 15 cmH2O at the outflow to the lymphatics had little effect on lymph flow. By comparison, Pv > 15 cmH2O slowed lymph flow by 55 +/- 29% relative to the lymph flow rate with zero outflow pressure. Thus Pv values > 15 cmH2O interfere with lymph flow from the sheep caudal mediastinal lymph node.

Relationship between intracranial pressure and cervical lymphatic pressure and flow rates in sheep

1999 ◽  
Vol 277 (6) ◽  
pp. R1712-R1717 ◽  
Author(s):  
I. Silver ◽  
B. Li ◽  
J. Szalai ◽  
M. Johnston
Keyword(s):  
Cerebrospinal Fluid ◽  
Intracranial Pressure ◽  
Jugular Vein ◽  
Lymphatic Vessels ◽  
Lymph Flow ◽  
Cranial Vault ◽  
Perfusion System ◽  
Flow Rates ◽  
Cisterna Magna ◽  
Mesenteric Lymph

Previous reports from our group demonstrated that about one-half of the total volume of cerebrospinal fluid (CSF) removed from the cranial vault in sheep is transported into extracranial lymphatics, especially cervical lymphatic vessels in the neck. In this study, we tested the hypothesis that an elevation of intracranial pressure (ICP) would increase cervical lymphatic pressure and lymph flow rates in anesthetized sheep. Catheters were inserted into both lateral ventricles, the cisterna magna, cervical lymphatics, and the jugular vein. A ventriculo-cisternal perfusion system was employed to regulate ICP. Mean ( P = 0.008), peak ( P = 0.007), and baseline ( P = 0.013) cervical lymphatic pressures increased as ICP was elevated from 10 to 70 cmH2O in 20-cmH2O increments. Similarly, cervical lymph flow rates increased ( P < 0.001), with flows at 70 cmH2O ICP observed to be approximately fourfold higher than those at 10 cmH2O ICP. No changes were observed in mesenteric lymph flow rates (vessels not expected to drain CSF). We conclude that cervical lymphatic vessels play an important role in the transport of CSF from the cranial vault when ICP is elevated.

Thoracic duct lymph flow and its measurement in chronically catheterized sheep fetus

1989 ◽  
Vol 256 (1) ◽  
pp. H16-H20 ◽  
Author(s):  
R. A. Brace
Keyword(s):  
Flow Rate ◽  
Thoracic Duct ◽  
Lymphatic Vessels ◽  
Lymph Flow ◽  
Thoracic Duct Lymph ◽  
Computer Technique ◽  
Venous Circulation ◽  
Duct Lymph ◽  
Unit Body Weight ◽  
Sheep Fetus

A method was developed for chronic catheterization of the left thoracic lymph duct at the base of the neck in the sheep fetus, which did not disrupt the other major lymphatic vessels that join the venous circulation at the same location. The lymphatic catheter was connected to a catheter in a jugular vein when lymph flow was not being recorded, so that the lymph continuously returned to the fetal circulation. Special consideration of catheter size to minimize flow resistance and treatment to prevent clotting were required. Individual animals were maintained up to 17 days with lymph flow continuing. In 13 fetuses averaging 128 days gestation (term = 147 days) at the time of catheterization, lymph flow rate was measured for 1 h each day for the first 7 postsurgical days with an on-line computer technique that continuously calculated lymph flow rate. Lymph flow averaged 0.64 +/- 0.17 (SD) ml/min in fetuses weighing 2.3-4 kg and tended to undergo a nonsignificant increase with time. Lymph and plasma protein concentrations did not change with time. In individual fetuses, large spontaneous variations in lymph flow rate occurred over periods of several seconds to a few minutes. Analysis showed that these variations in flow rate were not associated with fetal breathing movements. Thus the present study describes a technique for studying the dynamics of lymph flow in the unanesthetized sheep fetus in utero over a time period limited primarily by the length of gestation. In addition, it appears that thoracic duct lymph flow rate in the fetus per unit body weight averages three to four times that in the adult.

The Separation of Light Gaseous Isotopes by Mass Diffusion Columns II

1964 ◽  
Vol 19 (6) ◽  
pp. 747-755
Author(s):  
W. J. De Wet ◽  
J. Los
Keyword(s):  
Theoretical Analysis ◽  
Mass Diffusion ◽  
Experimental Results ◽  
The Other ◽  
Countercurrent Flow ◽  
Gas Solubility ◽  
Flow Rates ◽  
Mixing Effects ◽  
Other Hand ◽  
Good Agreement

The design of mass diffusion columns operated with partition membranes, for the separation of light gaseous isotopes, is discussed. A theoretical analysis of experimental results obtained indicates that a good agreement between experimental results and theory is only obtained at low column pressures and moderate countercurrent flow rates. At fairly low countercurrent flow rates mixing effects due to viscous dragging and gas solubility by the condensate appear to be considerable whereas excessively high countercurrent flow rates, on the other hand, also seem undesirable. Some suggestions are proposed to obviate impairing effects at least to some extent.

Intestinal lymphatic pressure increases during intravenous infusions in awake sheep

1993 ◽  
Vol 265 (3) ◽  
pp. R703-R705 ◽  
Author(s):  
R. E. Drake ◽  
Z. Anwar ◽  
S. Kee ◽  
J. C. Gabel
Keyword(s):  
Body Weight ◽  
Lymphatic System ◽  
Venous Pressure ◽  
Ringer Solution ◽  
Lymph Flow ◽  
The Body ◽  
Intravenous Fluid ◽  
Thoracic Duct Lymph ◽  
Duct Lymph ◽  
Intestinal Lymphatics

Intravenous fluid infusions cause increased venous pressure and increased lymph flow throughout the body. Together the increased lymph flow and increased venous pressure (the outflow pressure to the lymphatic system) should increase the pressure within the postnodal intestinal lymphatics. To test this, we measured the pressure in postnodal intestinal lymphatics and the neck vein pressure in five awake sheep. At baseline, the neck vein pressure was 1.2 +/- 1.5 (SD) cmH2O and the lymphatic pressure was 12.5 +/- 1.7 cmH2O. When we infused Ringer solution intravenously (10% body weight in approximately 50 min), the neck vein pressure increased to 17.3 +/- 0.9 cmH2O and the lymphatic pressure increased to 24.6 +/- 3.8 cmH2O (both P < 0.05). In two additional sheep, the thoracic duct lymph flow rate increased from 0.8 +/- 0.4 ml/min at baseline to 5.5 +/- 2.0 ml/min during the infusions. Our results show that postnodal intestinal lymphatic pressure may increase substantially during intravenous fluid infusions. This is important because increases in postnodal lymphatic pressure may slow lymph flow from the intestine.

Lymph pressure in rat intestinal lymph duct with lymphatic obstruction

1986 ◽  
Vol 251 (3) ◽  
pp. G321-G325 ◽  
Author(s):  
J. S. Lee
Keyword(s):  
Lymph Flow ◽  
Saline Infusion ◽  
Pressure Waves ◽  
Fluid Absorption ◽  
Intestinal Lymph ◽  
Intravenous Saline ◽  
Intestinal Lymphatics ◽  
Lymph Duct ◽  
Rhythmical Contractions ◽  
Lymphatic Obstruction

Lymph pressure (PL) in the main intestinal lymph duct with obstruction of lymph flow was determined. Under various conditions, the rate of lymph flow (JL) was essentially the same in either A rats (with communications between hepatic and intestinal lymphatics) or B rats (without such communications), but PL of A rats was significantly lower (P less than 0.01) than that of B rats. When the intestine was in the basal state, JL of A and B rats was 0.2-0.3 ml/h per rat, and PL was 1.5 +/- 0.2 and 3.3 +/- 0.2 mm/Hg, respectively. During fluid absorption, JL of A and B rats increased to 0.8-0.9 ml/h, and PL was 2.1 +/- 0.4 and 6.4 +/- 0.7 mmHg, respectively. During intravenous saline infusion, JL of A and B rats increased greatly to approximately 14 ml/h, and PL was 3.1 +/- 0.3 and 10.4 +/- 1.1 mmHg, respectively. The lower PL in A rats is apparently due to the possibility that during lymphatic obstruction most lymph could be drained off by the hepatic lymphatics. In A rats, luminal distension pressure had no effect on PL but in B rats PL decreased when distension pressure was 20 mmHg or higher. Furthermore, lymph pressure waves indicate the occurrence of rhythmical contractions of the lymph duct or its surrounding tissues, which may play a role in the propulsion of lymph.

Asymmetric [14C]albumin transport across bullfrog alveolar epithelium

1985 ◽  
Vol 59 (4) ◽  
pp. 1290-1297 ◽  
Author(s):  
K. J. Kim ◽  
T. R. LeBon ◽  
J. S. Shinbane ◽  
E. D. Crandall
Keyword(s):  
Alveolar Epithelium ◽  
Ringer Solution ◽  
The Other ◽  
Epithelial Barrier ◽  
Apparent Permeability ◽  
Simple Diffusion ◽  
Ussing Chambers ◽  
Alveolar Epithelial ◽  
Other Hand ◽  
Apparent Permeability Coefficient

Bullfrog lungs were prepared as planar sheets and bathed with Ringer solution in Ussing chambers. In the presence of a constant electrical gradient (20, 0, or -20 mV) across the tissue, 14C-labeled bovine serum albumin or inulin was instilled into the upstream reservoir and the rate of appearance of the tracer in the downstream reservoir was monitored. Two lungs from the same animal were used to determine any directional difference in tracer fluxes. An apparent permeability coefficient was estimated from a relationship between normalized downstream radioactivities and time. Results showed that the apparent permeability of albumin in the alveolar to pleural direction across the alveolar epithelial barrier is 2.3 X 10(-7) cm/s, significantly greater (P less than 0.0005) than that in the pleural to alveolar direction (5.3 X 10(-8) cm/s) when the tissue was short circuited. Permeability of inulin, on the other hand, did not show any directional dependence and averaged 3.1 X 10(-8) cm/s in both directions. There was no effect on radiotracer fluxes permeabilities of different electrical gradients across the tissue. Gel electrophoretograms and corresponding radiochromatograms suggest that the large and asymmetric isotope fluxes are not primarily due to digestion or degradation of labeled molecules. Inulin appears to traverse the alveolar epithelial barrier by simple diffusion through hydrated paracellular pathways. On the other hand, [14C]albumin crosses the alveolar epithelium more rapidly than would be expected by simple diffusion. These asymmetric and large tracer fluxes suggest that a specialized mechanism is present in alveolar epithelium that may be capable of helping to remove albumin from the alveolar space.

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