Intrinsic control of colonic blood flow and oxygenation

1980 ◽  
Vol 238 (6) ◽  
pp. G478-G484
Author(s):  
P. R. Kvietys ◽  
T. Miller ◽  
D. N. Granger
Keyword(s):  
Blood Flow ◽  
Vascular Resistance ◽  
Perfusion Pressure ◽  
Reactive Hyperemia ◽  
Venous Pressure ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Colonic Blood Flow ◽  
O2 Extraction ◽  
O2 Delivery

In a denervated autoperfused dog colon preparation, arterial perfusion pressure, venous outflow pressure, blood flow, and arteriovenous O2 difference were measured during graded arterial pressure alterations, arterial occlusion, venous pressure elevation, venous occlusion, and local intra-arterial infusion of adenosine. As perfusion pressure was reduced from 100 to 30 mmHg, colonic blood flow decreased and arteriovenous O2 difference increased. Although blood flow was not autoregulated O2 delivery was maintained within 10% of control between 70 to 100 mmHg and then decreased with further reduction in perfusion pressure. Arterial occlusion (15, 30, and 60 s) resulted in a postocclusion reactive hyperemia; the magnitude of the hyperemia was directly related to the duration of occlusion. Venous occlusion resulted in a postocclusion reactive hypoemia. Elevation of venous pressure from 0 to 20 mmHg increased vascular resistance, O2 extraction, and the capillary filtration coefficient, but decreased O2 delivery. Infusion of adenosine decreased vascular resistance and O2 extraction, but increased O2 delivery. These data suggest that both metabolic and myogenic mechanisms are involved in the control of colonic blood flow and oxygenation.

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.

ATP-sensitive K+ channel blockade impairs O2 extraction during progressive ischemia in pig hindlimb

1995 ◽  
Vol 79 (6) ◽  
pp. 2035-2042 ◽  
Author(s):  
B. Vallet ◽  
S. E. Curtis ◽  
B. Guery ◽  
J. Mangalaboyi ◽  
P. Menager ◽  
...  
Keyword(s):  
Blood Flow ◽  
Redox State ◽  
Perfusion Pressure ◽  
Glucose Solution ◽  
K Channel ◽  
Control Group ◽  
Cytochrome Aa3 ◽  
K Channels ◽  
O2 Extraction ◽  
O2 Delivery

Tissues maintain O2 consumption (VO2) when blood flow and O2 delivery (DO2) are decreased by better matching of blood flow to meet local cellular O2 demand, a process that increases extraction of available O2. This study tested the hypothesis that ATP-sensitive K+ channels play a significant role in the response of pig hindlimb to ischemia. We pump perfused the vascularly isolated but innervated right hindlimb of 14 anesthetized pigs with normoxic blood while measuring hindlimb DO2, VO2, perfusion pressure, and cytochrome aa3 redox state. In one-half of the pigs, the pump-perfused hindlimb was also infused with 10 micrograms.min-1.kg-1 of glibenclamide, a potent blocker of ATP-sensitive K+ channels. Control animals were infused with 5% glucose solution alone. Blood flow was then progressively reduced in both groups in 10 steps at 10-min intervals. Glibenclamide had no effect on any preischemic hindlimb or systemic measurements. Hindlimb VO2 and cytochrome aa3 redox state began to decrease at a significantly higher DO2 in glibenclamide-treated compared with control pigs. At this critical DO2, the O2 extraction ratio (VO2/DO2) was 53 +/- 4% in the glibenclamide group and 73 +/- 5% in the control group (P < 0.05). Hindlimb vascular resistance increased significantly with ischemia in the glibenclamide group but did not change in the control group. We conclude that ATP-sensitive K+ channels may be importantly involved in the vascular recruitment response that tried to meet tissue O2 needs as blood flow was progressively reduced in the pig hindlimb.

Effects of Hct and norepinephrine on segmental vascular resistance distribution in isolated perfused rat livers

2004 ◽  
Vol 286 (1) ◽  
pp. H121-H130 ◽  
Author(s):  
Chiaki Kamikado ◽  
Toshishige Shibamoto ◽  
Minoru Hongo ◽  
Shozo Koyama
Keyword(s):  
Blood Flow ◽  
Vascular Resistance ◽  
Venous Pressure ◽  
Regression Line ◽  
Venous Occlusion ◽  
Portal Venous Pressure ◽  
Venous Resistance ◽  
Four Levels ◽  
Rat Livers ◽  
Line Analysis

We studied the effects of blood hematocrit (Hct), blood flow, or norepinephrine on segmental vascular resistances in isolated portally perfused rat livers. Total portal hepatic venous resistance ( Rt) was assigned to the portal ( Rpv), sinusoidal ( Rsinus), and hepatic venous ( Rhv) resistances using the portal occlusion (Ppo) and the hepatic venous occlusion (Phvo) pressures that were obtained during occlusion of the respective line. Four levels of Hct (30%, 20%, 10%, and 0%) were studied. Rpv comprises 44% of Rt, 37% of Rsinus, and 19% of Rhv in livers perfused at 30% Hct and portal venous pressure of 9.1 cmH2O. As Hct increased at a given blood flow, all three segmental vascular resistances of Rpv, Rsinus, and Rhv increased at flow >15 ml/min. As blood flow increased at a given Hct, only Rsinus increased without changes in Rpv or Rhv. Norepinephrine increased predominantly Rpv, and, to a smaller extent, Rsinus, but it did not affect Rhv. Finally, we estimated Ppo and Phvo from the double occlusion maneuver, which occluded simultaneously both the portal and hepatic venous lines. The regression line analysis revealed that Ppo and Phvo were identical with those measured by double occlusion. In conclusion, changes in blood Hct affect all three segmental vascular resistances, whereas changes in blood flow affect Rsinus, but not Rpv or Rhv. Norepinephrine increases mainly presinusoidal resistance. Ppo and Phvo can be obtained by the double occlusion method in isolated perfused rat livers.

Effect of rhythmically inflating a pneumatic cuff at the ankle on blood flow in the foot

1959 ◽  
Vol 14 (3) ◽  
pp. 411-413 ◽  
Author(s):  
R. Andrew Loane
Keyword(s):  
Blood Flow ◽  
Heat Flow ◽  
Perfusion Pressure ◽  
Venous Pressure ◽  
Venous Occlusion ◽  
Quantitative Agreement ◽  
Venous Occlusion Plethysmography ◽  
Flow Through ◽  
And Calorimetry

Rhythmic inflation to 110 mm Hg of a pneumatic cuff around the ankle of a seated subject reduces the venous pressure in the foot and is found by three methods, venous occlusion plethysmography, heat flow and calorimetry, to increase the rate of blood flow through the foot. The increases measured by the three methods are not, however, in quantitative agreement and it is not possible to decide how large the increase may be. It is considered, however, that the increase in flow is probably of the same order as the increase in perfusion pressure and not greatly in excess of this increase. Submitted on August 5, 1958

Effects of hemodilution on gastric and intestinal oxygenation

1989 ◽  
Vol 256 (1) ◽  
pp. H171-H178 ◽  
Author(s):  
J. W. Kiel ◽  
G. L. Riedel ◽  
A. P. Shepherd
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Carrying Capacity ◽  
Pressure Range ◽  
Perfusion Pressure ◽  
O2 Consumption ◽  
O2 Uptake ◽  
O2 Extraction ◽  
The Right ◽  
O2 Delivery

To determine the effects of hemodilution on gastric and intestinal oxygenation, isolated segments of canine stomach and small bowel were perfused by a pressurized reservoir with blood at hematocrits of 40 and 20%. Arteriovenous O2 difference, blood flow, and arterial and venous pressures were monitored continuously as perfusion pressure was reduced in 30-mmHg steps from 180 to 30 mmHg. O2 consumption was calculated as the product of the steady-state arteriovenous O2 difference and blood flow at each perfusion pressure. Gastric and intestinal O2 uptake were relatively well maintained over most of the pressure range when the hematocrit was set at 40%. After hemodilution, gastric O2 uptake decreased significantly only at 90 and 60 mmHg, but intestinal O2 uptake was significantly reduced except at 30 mmHg. When gastric and intestinal O2 uptake were plotted as a function of blood flow, the O2 uptake vs. blood flow relationship were shifted down and to the right by hemodilution. Hemodilution also linearized the O2 uptake vs. blood flow relationship in the intestine. However, when O2 uptake was plotted as function of O2 delivery, the gastric O2 uptake vs. delivery curves at the two hematocrits were superimposed on each other, but the O2 uptake vs. delivery curves for the intestine diverged except at low rates of O2 delivery. We conclude that by reducing the O2-carrying capacity of the blood, hemodilution adversely affects gastric and intestinal oxygenation. Our results also indicate that hemodilution lowers gastric O2 uptake by reducing O2 delivery; however, hemodilution lowers intestinal O2 uptake not only by reducing O2 delivery but also by impairing O2 extraction.

Autoregulation of gastric blood flow and oxygen uptake

1981 ◽  
Vol 241 (2) ◽  
pp. G143-G149
Author(s):  
L. Holm-Rutili ◽  
M. A. Perry ◽  
D. N. Granger
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Arterial Pressure ◽  
Vascular Resistance ◽  
Perfusion Pressure ◽  
Venous Pressure ◽  
Oxygen Demand ◽  
Gastric Blood Flow ◽  
Oxygen Extraction ◽  
Sympathetic Denervation

The purpose of this study was to determine whether the ability of the stomach to autoregulate blood flow and oxygen uptake is altered by sympathetic denervation. Blood flow, oxygen extraction, local arterial pressure, and venous pressure were continuously monitored in sympathetically innervated and denervated autoperfused dog stomach preparations. As perfusion pressure was reduced in increments from 120 to 20 mmHg in innervated preparations, blood flow and oxygen uptake decreased while oxygen extraction and vascular resistance increased. Reductions in perfusion pressure in denervated preparations resulted in a decrease in blood flow, oxygen uptake, and vascular resistance, whereas oxygen extraction increased. The ability of the stomach to regulate blood flow and oxygen uptake was significantly improved after denervation, i.e., vascular resistance decreased and oxygen uptake remained relatively constant when arterial pressure was reduced. Oxygen uptake in denervated stomachs was generally higher than that in innervated stomachs. Autoregulation of gastric blood flow therefore appears to be improved by denervation. The better autoregulation observed after denervation may result either from a reduction in sympathetic tone and/or the increase in gastric oxygen demand.

Effect of short periods of arterial occlusion on blood flow and oxygen uptake

1961 ◽  
Vol 16 (5) ◽  
pp. 851-857 ◽  
Author(s):  
David I. Abramson ◽  
Samuel Tuck ◽  
Yvonne Bell ◽  
Roscoe E. Mitchell ◽  
Agenor M. Zayas
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Reactive Hyperemia ◽  
Arterial Occlusion ◽  
Normal Subjects ◽  
Venous Occlusion ◽  
Oxygen Debt ◽  
Base Line ◽  
Vascular Change ◽  
Fick Principle

In 17 experiments, performed on the forearm of normal subjects, the effect of 2½, 5, and 10 min of arterial occlusion was studied. Blood flow was obtained with the venous occlusion plethysmograph, and oxygen uptake was calculated using the Fick principle. Arterial occlusion resulted in the production of an oxygen debt which was subsequently repaid. With progressively longer periods of anoxia there was a proportionate increase in the magnitude of the debt. Similar conclusions could not be drawn from blood flow studies alone, since the vascular change represented only one means of repayment of the oxygen debt during reactive hyperemia, the other being a greater extraction of oxygen from each unit of blood early in the postocclusion period. The constant overswing on either side of the control base line, observed in the records of oxygen uptake, suggested the absence of delicately balanced and efficient checks on the mechanisms responsible for repayment of the oxygen debt incurred in the period of tissue anoxia. Submitted on March 27, 1961

Diaphragmatic perfusion heterogeneity during exercise with inspiratory resistive breathing

1990 ◽  
Vol 68 (5) ◽  
pp. 2177-2181 ◽  
Author(s):  
M. Manohar
Keyword(s):  
Blood Flow ◽  
Exercise Capacity ◽  
Vascular Resistance ◽  
Maximal Exercise ◽  
Perfusion Pressure ◽  
Work Of Breathing ◽  
Regional Distribution ◽  
Resistive Breathing ◽  
Exercise Induced

Regional distribution of diaphragmatic blood flow (Q; 15-microns-diam radionuclide-labeled microspheres) was studied in normal (n = 7) and laryngeal hemiplegic (LH; n = 7) ponies to determine whether the added stress of inspiratory resistive breathing during maximal exercise may cause 1) redistribution of diaphragmatic Q and 2) crural diaphragmatic Q to exceed that in maximally exercising normal ponies. LH-induced augmentation of already high exertional work of breathing resulted in diminished locomotor exercise capacity so that maximal exercise in LH ponies occurred at 25 km/h compared with 32 km/h for normal ponies. The costal and crural regions received similar Q in both groups at rest. However, exercise-induced increments in perfusion were significantly greater in the costal region of the diaphragm. At 25 km/h, costal diaphragmatic perfusion was 154 and 143% of the crural diaphragmatic Q in normal and LH ponies. At 32 km/h, Q in costal diaphragm of normal ponies was 136% of that in the crural region. Costal and crural diaphragmatic Q in LH ponies exercised at 25 km/h exceeded that for normal ponies but was similar to the latter during exercise at 32 km/h. Perfusion pressure for the three conditions was also similar. It is concluded that diaphragmatic perfusion heterogeneity in exercising ponies was preserved during the added stress of inspiratory resistive breathing. It was also demonstrated that vascular resistance in the crural and costal regions of the diaphragm in maximally exercised LH ponies remained similar to that in maximally exercising normal ponies.

Analysis of oxygen delivery and uptake relationships in the Krogh tissue model

1989 ◽  
Vol 67 (3) ◽  
pp. 1234-1244 ◽  
Author(s):  
P. T. Schumacker ◽  
R. W. Samsel
Keyword(s):  
Blood Flow ◽  
Critical Point ◽  
Real Data ◽  
Whole Body ◽  
O2 Uptake ◽  
Highly Sensitive ◽  
O2 Extraction ◽  
O2 Supply ◽  
Experimental Findings ◽  
O2 Delivery

Normally, tissue O2 uptake (VO2) is set by metabolic activity rather than O2 delivery (QO2 = blood flow X arterial O2 content). However, when QO2 is reduced below a critical level, VO2 becomes limited by O2 supply. Experiments have shown that a similar critical QO2 exists, regardless of whether O2 supply is reduced by progressive anemia, hypoxemia, or reduction in blood flow. This appears inconsistent with the hypothesis that O2 supply limitation must occur by diffusion limitation, since very different mixed venous PO2 values have been seen at the critical point with hypoxic vs. anemic hypoxia. The present study sought to begin clarifying this paradox by studying the theoretical relationship between tissue O2 supply and uptake in the Krogh tissue cylinder model. Steady-state O2 uptake was computed as O2 delivery to tissue representative of whole body was gradually lowered by anemic, hypoxic, or stagnant hypoxia. As diffusion began to limit uptake, the fall in VO2 was computed numerically, yielding a relationship between QO2 and VO2 in both supply-independent and O2 supply-dependent regions. This analysis predicted a similar biphasic relationship between QO2 and VO2 and a linear fall in VO2 at O2 deliveries below a critical point for all three forms of hypoxia, as long as intercapillary distances were less than or equal to 80 microns. However, the analysis also predicted that O2 extraction at the critical point should exceed 90%, whereas real tissues typically extract only 65–75% at that point. When intercapillary distances were larger than approximately 80 microns, critical O2 extraction ratios in the range of 65–75% could be predicted, but the critical point became highly sensitive to the type of hypoxia imposed, contrary to experimental findings. Predicted gas exchange in accord with real data could only be simulated when a postulated 30% functional peripheral O2 shunt (arterial admixture) was combined with a tissue composed of Krogh cylinders with intercapillary distances of less than or equal to 80 microns. The unrealistic efficacy of tissue O2 extraction predicted by the Krogh model (in the absence of postulated shunt) may be a consequence of the assumed homogeneity of tissues, because real tissues exhibit many forms of heterogeneity among capillary units. Alternatively, the failure of the original Krogh model to fully predict tissue O2 supply dependency may arise from basic limitations in the assumptions of that model.

Lower vascular tone and larger plasma volume in Parkinson's disease with orthostatic hypotension

2011 ◽  
Vol 111 (2) ◽  
pp. 443-448 ◽  
Author(s):  
J. T. Groothuis ◽  
R. A. J. Esselink ◽  
J. P. H. Seeger ◽  
M. J. H. van Aalst ◽  
M. T. E. Hopman ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Blood Flow ◽  
Orthostatic Hypotension ◽  
Vascular Resistance ◽  
Plasma Volume ◽  
Venous Pressure ◽  
Dilution Method ◽  
Significant Difference ◽  
Head Up Tilt

The pathophysiology of orthostatic hypotension in Parkinson's disease (PD) is incompletely understood. The primary focus has thus far been on failure of the baroreflex, a central mediated vasoconstrictor mechanism. Here, we test the role of two other possible factors: 1) a reduced peripheral vasoconstriction (which may contribute because PD includes a generalized sympathetic denervation); and 2) an inadequate plasma volume (which may explain why plasma volume expansion can manage orthostatic hypotension in PD). We included 11 PD patients with orthostatic hypotension (PD + OH), 14 PD patients without orthostatic hypotension (PD − OH), and 15 age-matched healthy controls. Leg blood flow was examined using duplex ultrasound during 60° head-up tilt. Leg vascular resistance was calculated as the arterial-venous pressure gradient divided by blood flow. In a subset of 9 PD + OH, 9 PD − OH, and 8 controls, plasma volume was determined by indicator dilution method with radiolabeled albumin (125I-HSA). The basal leg vascular resistance was significantly lower in PD + OH (0.7 ± 0.3 mmHg·ml−1·min) compared with PD − OH (1.3 ± 0.6 mmHg·ml−1·min, P < 0.01) and controls (1.3 ± 0.5 mmHg·ml−1·min, P < 0.01). Leg vascular resistance increased significantly during 60° head-up tilt with no significant difference between the groups. Plasma volume was significantly larger in PD + OH (3,869 ± 265 ml) compared with PD − OH (3,123 ± 377 ml, P < 0.01) and controls (3,204 ± 537 ml, P < 0.01). These results indicate that PD + OH have a lower basal leg vascular resistance in combination with a larger plasma volume compared with PD − OH and controls. Despite the increase in leg vascular resistance during 60° head-up tilt, PD + OH are unable to maintain their blood pressure.

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