The Effects of the Tracheal Pressure Upon Flow: Pressure Relations in the Vascular Bed of Isolated Lungs

Banister, Jean; Torrance, R. W.

doi:10.1113/expphysiol.1960.sp001491

Cited by 73 publications

(22 citation statements)

References 6 publications

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“…6 Swan-Ganz catheter, passed through a hindlimb artery, in the descending aorta of the ewe; a No. 4 Fogarty embolectomy catheter in the fetal descending aorta; and a balloon catheter, 1.4 cm in diameter, constructed from a polyvinyl tube (o.d., 0.254 cm) in the inferior vena cava of the ewe proximal to the entry of the uterine veins. The end hole of a No.…”

Section: Methodsmentioning

confidence: 99%

Relationships between pressure and flow in the umbilical and uterine circulations of the sheep.

Berman¹,

Goodlin²,

Heymann³

et al. 1976

Circulation Research

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SUMMARY We studied the relationship of fetal and maternal vascular pressures to umbilical and uterine blood flow in the unanesthetized ewe and in the sheep fetus in utero by placing electromagnetic flow transducers around both the common umbilical and uterine arteries. Reductions in umbilical arterial pressure or elevations in umbilical venous pressure decreased umbilical blood flow without affecting either the uterine arterial blood flow or other maternal cardiovascular variables which were studied. Elevations in uterine venous pressure or reductions in uterine arterial pressure decreased uterine arterial flow but these interventions had no effect on umbilical blood flow until fetal hypoxemia and bradycardia occurred. When the bradycardia of the fetal hypoxic response was inhibited by atropine, alterations in maternal vascular pressure had no effect on umbilical arterial flow. These data do not support the presence of a "sluice" or "waterfall" effect in the umbilical-placental circulation of the sheep fetus in utero.THE Poiseuille-Hagen law, which describes the relationship of flow, resistance, and perfusion pressure in rigid tubes, conventionally is used to analyze organ blood flow.' Recently both theoretical 2 -3 and other experimental'-5 analyses have defined another hemodynamic system variously termed the waterfall, 5 capilleron, 6 or sluice 7 model. This model states that blood flow (Q 1 ) through a system of collapsible channels which are surrounded by a pressure (P c ) exceeding venous outflow pressure (P o ) is directly proportional to the difference between inflow pressure (P t ) and surrounding pressure (P c ), and inversely proportional to the resistance of the rigid vascular elements (/?), but is unaffected by outflow pressure (P o ) as long as P o is lower than Pc-Q' = (Pt -Pc)/R, when P c > P o .Power and Longo 7 and Motoyama et al. 8 proposed that the uterine vascular system that surrounds the umbilical circulation of the sheep fetus generates a placental tissue pressure; this exceeds umbilical venous pressure and thereby regulates umbilical blood flow by this sluice mechanism. Their conclusions are based on experimental data obtained from acute studies, most of which involved perfusion of isolated placentomes.To test the validity of the waterfall theory in vivo and study the relationship of fetal and maternal vascular pressures to umbilical and uterine blood flow in the sheep, we developed a preparation for the study of variables affecting placental flows in the standing, unanesthetized ewe and the fetal lamb in utero. MethodsOperations were performed on 18 pregnant Western ewes with time-dated gestations of 100-140 days. They were Received June 23, 1975; accepted for publication October 28, 1975. fasted 24-48 hours, given epidural anesthesia with 2 ml of 1% tetracaine HC1 (20 mg), and placed supine on the operating table. Polyvinyl catheters (inner diameter, 0.132 cm; outer diameter, 0.229 cm) were inserted through the maternal femoral artery and vein and advanced into the descending aorta a...

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Section: Methodsmentioning

confidence: 99%

Relationships between pressure and flow in the umbilical and uterine circulations of the sheep.

Berman¹,

Goodlin²,

Heymann³

et al. 1976

Circulation Research

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“…Most of the lungs (34) were frozen while being perfused under vascular waterfall conditions (zone II, analagous to flow through a Starling resistor model), that is, inflow pressure exceeded alveolar pressure, but alveolar pressure was greater than outflow pressure. Under these conditions the collapsible vessels exposed to alveolar pressure (capillaries or very small arterioles or venules depending on the direction of flow) develop a constriction in their downstream end (7,8); this we refer to as the collapse point. Driving pressure is thus inflow-alveolar pressure rather than the conventional inflow-outflow pressure.…”

Section: Methods Preparationmentioning

confidence: 99%

Sites of pulmonary vasomotor reactivity in the dog during alveolar hypoxia and serotonin and histamine infusion

Glazier¹,

Murray²

1971

J. Clin. Invest.

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“…To solve the equation (6) and (7) under the boundary conditions (9) and (10), we make use of the following non-…”

Section: Solution Of the Problemmentioning

confidence: 99%

“…This understanding is based upon the analogy of the steady flow through a vascular system with the flow through an elastic tube (see for details, Guyton [7], Brecher [8], Banister and Torrance [9] and Permutt et al [10]). Such a tube is named a Starling resistor because of its introduction as a laboratory device for simulating the resistance of the vascular system (see Knowlton and Starling [11]).…”

Section: Introductionmentioning

confidence: 99%

Mathematical model for a Herschel-Bulkley fluid flow in an elastic tube

et al. 2011

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Abstract:The constitution of blood demands a yield stress fluid model, and among the available yield stress fluid models for blood flow, the Herschel-Bulkley model is preferred (because Bingham, Power-law and Newtonian models are its special cases). The Herschel-Bulkley fluid model has two parameters, namely the yield stress and the power law index. The expressions for velocity, plug flow velocity, wall shear stress, and the flux flow rate are derived. The flux is determined as a function of inlet, outlet and external pressures, yield stress, and the elastic property of the tube. Further when the power-law index = 1 and the yield stress τ 0 → 0, our results agree well with those of Rubinow and Keller [J. Theor. Biol. 35, 299 (1972)]. Furthermore, it is observed that, the yield stress and the elastic parameters ( 1 and 2 ) have strong effects on the flux of the non-Newtonian fluid flow in the elastic tube. The results obtained for the flow characteristics reveal many interesting behaviors that warrant further study on the non-Newtonian fluid flow phenomena, especially the shear-thinning phenomena. Shear thinning reduces the wall shear stress.

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The Effects of the Tracheal Pressure Upon Flow: Pressure Relations in the Vascular Bed of Isolated Lungs

Cited by 73 publications

References 6 publications

Relationships between pressure and flow in the umbilical and uterine circulations of the sheep.

Relationships between pressure and flow in the umbilical and uterine circulations of the sheep.

Sites of pulmonary vasomotor reactivity in the dog during alveolar hypoxia and serotonin and histamine infusion

Mathematical model for a Herschel-Bulkley fluid flow in an elastic tube

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