A new method for estimating skeletal muscle capillary pressure

1984 ◽  
Vol 246 (6) ◽  
pp. H880-H885
Author(s):  
R. J. Korthuis ◽  
D. N. Granger ◽  
A. E. Taylor
Keyword(s):  
Skeletal Muscle ◽  
Capillary Pressure ◽  
Venous Pressure ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Fluid Filtration ◽  
Arterial Inflow ◽  
Capillary Pressures ◽  
Highly Correlated ◽  
Artificial Plasma

Venous (Pc,vo) and arterial occlusion capillary pressures were simultaneously compared with isogravimetric capillary pressure (Pci) in isolated rat hindquarters and canine gracilis muscles perfused with blood or an artificial plasma. Arterial or venous pressure transients following rapid occlusion of arterial inflow or venous outflow, respectively, were analyzed for the inflection point between rapid and slow components. This transition point was assumed to represent the beginning of discharge of blood stored in (arterial occlusion) or the addition of blood to (venous occlusion) skeletal muscle microvessels and was defined as the effective capillary pressure. In all preparations, Pc,vo was identical to Pci. Arterial occlusion pressures were the same as Pci and Pc,vo in artificial plasma-perfused preparations but were significantly greater (P less than 0.01) than Pci and Pc,vo obtained in blood-perfused preparations. This inequality between arterial occlusion pressure and Pci may be related to a critical closure of small precapillary vessels or the non-Newtonian behavior of blood. In addition, venous occlusion pressures were highly correlated (r = 0.95, P less than 0.01) to calculated capillary pressures obtained following simultaneous equivalent elevations of arterial and venous pressure. These results indicate that the primary sites of vascular compliance and fluid filtration reside at or very near one another in the skeletal muscle microcirculation and that the more easily determined venous occlusion capillary pressure is an adequate measure of the effective capillary pressure in skeletal muscle.

A new method for estimating intestinal capillary pressure

1983 ◽  
Vol 244 (3) ◽  
pp. G341-G344 ◽  
Author(s):  
D. N. Granger ◽  
M. A. Perry ◽  
P. R. Kvietys ◽  
A. E. Taylor
Keyword(s):  
Capillary Pressure ◽  
Simple Technique ◽  
Venous Pressure ◽  
Venous Occlusion ◽  
Fluid Filtration ◽  
Intestinal Microcirculation ◽  
Highly Correlated ◽  
Outflow Cannula ◽  
Stop Flow ◽  
Flow Capillary

The purpose of this study was to compare the venous occlusion method for measuring capillary pressure with the stop-flow isovolumetric method in the cat small intestine. Venous occlusion pressures were determined from the inflection point of the venous pressure tracing after sudden occlusion of the venous outflow cannula. Venous occlusion pressure was highly correlated (r = 0.98, P less than 0.01) with stop-flow capillary pressure. This finding indicates that the major sites of fluid filtration and vascular capacitance reside at the same segment of the intestinal microcirculation. The venous occlusion method is a relatively simple technique for measuring whole-organ capillary pressure that is not constrained by the technical difficulties associated with volumetric/gravimetric techniques.

Microvascular control of capillary pressure during increases in local arterial and venous pressure

1988 ◽  
Vol 254 (4) ◽  
pp. H772-H784 ◽  
Author(s):  
M. J. Davis
Keyword(s):  
Hydrostatic Pressure ◽  
Capillary Pressure ◽  
Venous Pressure ◽  
The Body ◽  
Cell Velocity ◽  
Arterial Inflow ◽  
Tissue Act ◽  
Pallid Bats ◽  
Red Cell Velocity ◽  
Capillary Pressures

The extent to which capillary hydrostatic pressure might be protected from increases in local arterial and venous pressure was examined in the wing microcirculation of unanesthetized pallid bats (Antrozous pallidus). Arterial inflow and venous outflow pressures to the wing were elevated using a box technique to increase pressure around the body of the animal in steps of 12 mmHg between 0 and +60 mmHg for 3-min periods. During this time, hydrostatic pressure, diameter, and red cell velocity in single microvessels were continuously recorded. All branching orders of arterioles constricted significantly during increases in box pressure (Pb), while capillaries and venules dilated. First-order arteriole and venule pressures increased 1:1 with Pb. Capillary pressures increased by only a fraction of Pb up to +36 mmHg, but at higher Pb, the change in capillary pressure was equivalent to the change in Pb. Calculations of vascular resistance indicate that changes in both pre- and postcapillary resistance in this tissue act to prevent increases in capillary pressure during moderate, but not during large, increases in arterial and venous pressure.

Autoregulation of capillary pressure and filtration rate in isolated rat hindquarters

1985 ◽  
Vol 248 (6) ◽  
pp. H835-H842 ◽  
Author(s):  
R. J. Korthuis ◽  
D. N. Granger ◽  
M. I. Townsley ◽  
A. E. Taylor
Keyword(s):  
Skeletal Muscle ◽  
Arterial Pressure ◽  
Capillary Pressure ◽  
Filtration Rate ◽  
Venous Occlusion ◽  
Aortic Pressure ◽  
Capillary Filtration ◽  
Abdominal Aortic ◽  
Capillary Pressures ◽  
Isolated Rat

The hypothesis that skeletal muscle capillary pressure and/or capillary filtration rate are autoregulated was tested in 10 isolated rat hindquarters. Capillary pressure was directly assessed with the venous occlusion technique as abdominal aortic pressure was reduced in 25-mmHg decrements from 125 to 25 mmHg. Capillary pressure was not altered by reduction of arterial pressure from 125 to 100 mmHg, but it decreased progressively when arterial pressure was reduced from 100 to 25 mmHg. As perfusion pressure was reduced, capillary filtration rate decreased progressively, while the capillary filtration coefficient increased. The progressive decrease in capillary pressures was less than that predicted for a totally passive system, implying that capillary pressure was autoregulated to some degree. However, analysis of pre- to postcapillary resistance ratios suggested that the degree of capillary pressure autoregulation was minimal when perfusion pressures varied over a range of 100–25 mmHg. Capillary filtration rate was maintained better than would be predicted from the measured fall in capillary pressure by readjustments of interstitial Starling forces. These results indicate that capillary pressure is poorly autoregulated in rat skeletal muscle but that compensatory readjustments in interstitial Starling forces help maintain fluid balance and prevent excess dehydration of the interstitium of skeletal muscle as arterial pressure is reduced.

Validation of double vascular occlusion method for Pc,i in lung and skeletal muscle

1986 ◽  
Vol 61 (1) ◽  
pp. 127-132 ◽  
Author(s):  
M. I. Townsley ◽  
R. J. Korthuis ◽  
B. Rippe ◽  
J. C. Parker ◽  
A. E. Taylor
Keyword(s):  
Skeletal Muscle ◽  
Vascular Tone ◽  
Vascular Occlusion ◽  
Occlusion Pressure ◽  
Maximal Dilatation ◽  
Wide Range ◽  
Occlusion Technique ◽  
Capillary Pressures ◽  
Highly Correlated ◽  
Artificial Plasma

Capillary pressures in isogravimetric lung and skeletal muscle measured with the double vascular occlusion technique (Pdo) were compared to those measured using the traditional gravimetric technique (Pc,i). Pressures were measured using both techniques in isolated blood-perfused canine lungs (n = 18), blood-perfused rat hindquarters before (n = 8) and after (n = 6) maximal dilatation with papaverine and in rat hindquarters perfused with an artificial plasma (n = 6). In both organs, regardless of vascular tone, the double vascular occlusion isogravimetric pressure was the same as the gravimetric Pc,i, and the two measurements were highly correlated. Lung: Pdo = -0.22 + 1.06 Pc,i (r = 0.85, P less than 0.01); hindquarter: Pdo = -1.03 + 0.99 Pc,i (r = 0.91, P less than 0.01). In addition, Pdo was the same at every combination of isogravimetric arterial and venous pressures tested. The results indicate that the more rapidly applied double vascular occlusion pressure yields an accurate measure of isogravimetric capillary pressure in isolated organs over a wide range of isogravimetric pressures.

Estimation of isogravimetric capillary pressure by a filtration method in skeletal muscle and lung

1984 ◽  
Vol 57 (6) ◽  
pp. 1817-1823 ◽  
Author(s):  
R. J. Korthuis ◽  
M. I. Townsley ◽  
B. Rippe ◽  
A. E. Taylor
Keyword(s):  
Skeletal Muscle ◽  
Capillary Pressure ◽  
Whole Blood ◽  
Experimental Conditions ◽  
Filtration Method ◽  
Capillary Pressures ◽  
Artificial Plasma ◽  
Isolated Rat

Pre- to postcapillary resistance ratios (Ra/Rv) and isogravimetric capillary pressures (Pc,i) were estimated using a modified filtration method and compared with estimates obtained by application of traditional isogravimetric techniques in isolated rat hindquarters and canine lungs. Pc,i's and Ra/Rv's were estimated using both methods in rat hindquarters perfused with whole blood or an artificial plasma and in blood-perfused canine lung. In each of the three experimental conditions studied, the modified filtration method yielded the same Pc,i and Ra/Rv as the isogravimetric technique. Maximal vasodilation of the rat hindquarter with papaverine reduced Ra/Rv approximately fourfold to a level which was not different from that obtained in hindquarters perfused with artificial plasma, although Pc,i was unchanged. These results indicate that the more easily applied modified filtration method provides an excellent measurement of Ra/Rv and Pc,i in whole organ studies.

Vascular pressure effects on lung edema formation after glass bead embolism

1987 ◽  
Vol 62 (5) ◽  
pp. 1989-1996 ◽  
Author(s):  
I. C. Ehrhart ◽  
J. E. Hall ◽  
W. F. Hofman
Keyword(s):  
Capillary Pressure ◽  
Glass Bead ◽  
Venous Pressure ◽  
Venous Occlusion ◽  
Pressure Effects ◽  
Lung Edema ◽  
Edema Formation ◽  
Fluid Filtration ◽  
Lung Lobe ◽  
Microvessel Wall

The canine lung lobe was embolized with 100-micron glass beads before lobectomy and blood anticoagulation. The lobe was isolated, ventilated, and pump-perfused with blood at an arterial pressure (Pa) of about 50 (high pressure, HP, n = 9) or 25 Torr (low pressure, LP, n = 9). Rus/PVR, the ratio of upstream (Rus) to total lobar vascular resistance (PVR), was determined by venous occlusion and the isogravimetric capillary pressure technique. The capillary filtration coefficient (Kf), an index of vascular permeability, was obtained from rate of lobe weight gain during stepwise capillary pressure (Pc) elevation. The embolized lobes became more edematous than nonembolized controls, (C, n = 11), (P less than 0.05), with Kf values of 0.20 +/- 0.04, 0.25 +/- 0.06, and 0.07 +/- 0.01 ml X min-1 X Torr-1 X 100 X g-1 in LP, HP, and C, respectively (P less than 0.05). The greater Rus/PVR in embolized lobes (P less than 0.05) protected the microvessels and, although Pc was greater in HP than in controls (P less than 0.05), Pc did not differ between HP and LP (P greater than 0.05). Although indexes of permeability did not differ between embolized groups (P greater than 0.05), HP became more edematous than LP (P less than 0.05). The greater edema in HP did not appear due to a greater imbalance of Starling forces across the microvessel wall or to vascular recruitment. At constant Pc and venous pressure, elevating Pa from 25 to 50 Torr in embolized lobes resulted in greater edema to suggest fluid filtration from precapillary vessels.

Comparison of isogravimetric and venous occlusion capillary pressures in isolated dog lungs

1983 ◽  
Vol 55 (3) ◽  
pp. 964-968 ◽  
Author(s):  
J. C. Parker ◽  
P. R. Kvietys ◽  
K. P. Ryan ◽  
A. E. Taylor
Keyword(s):  
Capillary Pressure ◽  
Pulmonary Circulation ◽  
Balloon Catheter ◽  
Venous Occlusion ◽  
Regression Equation ◽  
Adequate Measure ◽  
Capillary Filtration ◽  
Filtration Pressure ◽  
Capillary Pressures ◽  
Highly Correlated

Venous occlusion capillary pressures (Pcv) were simultaneously compared with isogravimetric capillary pressures (PcI) in the same isolated perfused dog lung preparations. For 26 determinations, PcI averaged 1.23 +/- 0.22 (SE) mmHg higher than Pcv. However, the two measurements of capillary pressure were highly correlated (r = 0.99), and the following regression equation was obtained: Pcv = 1.12 PcI - 2.1. Pcv could be easily measured several times in the same preparation, either by total venous occlusion or regional venous occlusion using a Swan-Ganz balloon catheter. In addition, Pcv did not require an isogravimetric state for its determination. These data suggest that the major sites of filtration and vascular capacitance in the pulmonary circulation reside in the microvessels and that the more easily determined Pcv is an adequate measure of the average capillary filtration pressure in the lungs.

Peak calf blood flow estimates are higher with Dohn than with Whitney plethysmograph

1996 ◽  
Vol 81 (3) ◽  
pp. 1418-1422 ◽  
Author(s):  
D. N. Proctor ◽  
J. R. Halliwill ◽  
P. H. Shen ◽  
N. E. Vlahakis ◽  
M. J. Joyner
Keyword(s):  
Blood Flow ◽  
Reactive Hyperemia ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Calf Blood Flow ◽  
Absolute Flow ◽  
Wide Range ◽  
Before And After ◽  
The Mean ◽  
Highly Correlated

Estimates of calf blood flow with venous occlusion plethysmography vary widely between studies, perhaps due to the use of different plethysmographs. Consequently, we compared calf blood flow estimates at rest and during reactive hyperemia in eight healthy subjects (four men and four women) with two commonly used plethysmographs: the mercury-in-silastic (Whitney) strain gauge and Dohn air-filled cuff. To minimize technical variability, flow estimates were compared with a Whitney gauge and a Dohn cuff on opposite calves before and after 10 min of bilateral femoral arterial occlusion. To account for any differences between limbs, a second trial was conducted in which the plethysmographs were switched. Resting flows did not differ between the plethysmographs (P = 0.096), but a trend toward lower values with the Whitney was apparent. Peak flows averaged 37% lower with the Whitney (27.8 +/- 2.8 ml.dl-1.min-1) than with the Dohn plethysmograph (44.4 +/- 2.8 ml.dl-1.min-1; P < 0.05). Peak flow expressed as a multiple above baseline was also lower with the Whitney (10-fold) than with the Dohn plethysmograph (14.5-fold; P = 0.02). Across all flows at rest and during reactive hyperemia, estimates were highly correlated between the plethysmographs in all subjects (r2 = 0.96-0.99). However, the mean slope for the Whitney-Dohn relationship was only 60 +/- 2%, indicating that over a wide range of flows the Whitney gauge estimate was 40% lower than that for the Dohn cuff. These results demonstrate that the same qualitative results can be obtained with either plethysmograph but that absolute flow values will generally be lower with Whitney gauges.

Criteria for analysis of arterial and venous occlusion

1991 ◽  
Vol 70 (2) ◽  
pp. 665-675 ◽  
Author(s):  
T. S. Hakim
Keyword(s):  
Autologous Blood ◽  
Venous Pressure ◽  
Venous Occlusion ◽  
Pressure Gradients ◽  
Experimental Conditions ◽  
Pressure System ◽  
Arterial Inflow ◽  
Outflow Rate ◽  
Set Up

To provide a better understanding of analysis of arterial (AO) and venous occlusion (VO) tracings, using a constant and nonpulsatile perfusion pressure system, we set up an isolated in situ dog lobe preparation perfused with autologous blood. Four signals were recorded: arterial pressure, arterial inflow rate, venous pressure, and venous outflow rate. The four signals were recorded into the memory of a computer. When flow into the lobe was abruptly stopped (AO), flow out of the lung continued unchanged for approximately 150 ms and then decreased slowly to zero. Likewise, when flow out of the lung was abruptly stopped (VO), the flow into the lung continued unchanged for approximately 130 ms and then decreased slowly to zero. A monoexponential curve was fitted to different stretches of data between 0.1 and 5 s postocclusion and extrapolated to the instant of occlusion (defined here as the instant when flow at the site of occlusion becomes zero). The results indicate that 1) the first 150 ms postocclusion should be avoided because of the oscillatory artifacts generated by the occlusion maneuver, 2) use of a long segment of postocclusion data (5 s) tends to underestimate the middle pressure gradient and overestimate the arterial and venous pressure gradients, and 3) the changes in segmental vascular resistance under different experimental conditions were found to be unaffected by the criteria of analysis. Analysis of the postocclusion (AO and VO) tracings was found to be most compatible with the double-occlusion capillary pressure by fitting a stretch of data between 0.2 and 2.5 s postocclusion and extrapolating back to the instant when flow becomes zero at the site of occlusion but no earlier.

Partitioning of pulmonary vascular resistance in dogs by arterial and venous occlusion

1982 ◽  
Vol 52 (3) ◽  
pp. 710-715 ◽  
Author(s):  
T. S. Hakim ◽  
R. P. Michel ◽  
H. K. Chang
Keyword(s):  
Flow Rate ◽  
Venous Pressure ◽  
Venous Occlusion ◽  
Pulmonary Vasculature ◽  
Pressure Drops ◽  
Lower Lung ◽  
Arterial Inflow ◽  
Arteries And Veins ◽  
Lung Lobes

We perfused in situ isolated left lower lung lobes at a steady flow rate in zone 3 condition. When the lobar arterial inflow was suddenly occluded, the arterial pressure (Pa) fell rapidly and then more slowly. When the lobar venous outflow was suddenly occluded, the venous pressure (Pv) rose rapidly and then continued to rise more slowly. The rapid changes in Pa and Pv with inflow and outflow occlusion, respectively, represent the pressure drops across the arterial (delta Pa) and venous (delta Pv) relatively indistensible vessels. The total arteriovenous pressure difference (delta Pt) minus delta Pa + delta Pv gives the pressure drop across the vessels in the middle (delta Pm) that are much more distensible. Serotonin and histamine infusion increased delta Pa and delta Pv, respectively, but left delta Pm unchanged. delta Pa and delta Pv, but not delta Pm, increased as flow rate was increased. The studies with varying flow rate and venous pressures suggested that the arteries and veins became resistant to distension when their transmural pressures exceeded 10--5 Torr, respectively. Under the conditions studied, the middle nonmuscular segment contributed a major fraction of the vascular compliance and less than 16% of the total resistance. The muscular arteries and veins contributed equally to the remaining resistance. We conclude that the arterial and venous occlusion method is a useful technique to describe the resistance and compliance of different segments of the pulmonary vasculature.

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