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87 Cards in this Set
- Front
- Back
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This is a multi-branched elastic conduit set into oscillation by each beat of the heart.
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Arterial System
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In a normal adult heart, how much blood is pumped into the Aorta with each beat?
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70 milliliters
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Describe what happens to blood pressure and flow with each contraction of the LV
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Pressure in the LV rises
AV opens once LV pressure exceeds aortic pressure Blood is ejected into the AO, causing a rise in BP |
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What happens to blood pressure with an increase in heart rate?
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BP increases
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Describe the route of blood from the LV to the RA
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LV
Aorta Large Arteries Arterioles Capillaries Venules Large Veins Vena Cava RA |
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The amount of blood ejected from the LV with each contraction is called what?
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Stroke Volume
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What effect do cardiac contractions have on the pressure gradient between arteries and veins? Why?
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Cardiac contractions increase blood volume in arteries, which helps maintain a high pressure gradient between arteries and veins.
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What determines the amount of blood in the arterial system?
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Cardiac Output
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What determines the amount of blood that leaves the arterial system?
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Arterial pressure
Peripheral Resistance |
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Where is blood pressure the greatest and least?
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> Proximal to the heart
< Distal to the heart |
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Movement of fluid between two points requires what two things?
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1. Vessel/Pathway
2. Pressure difference (between origin and destination) |
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The amount of flow depends on what two things?
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1. Pressure/Energy difference
2. Resistance |
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What is the relationship between resistance and flow rate?
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Inversely Proportional
< resistance = > flow > resistance = < flow |
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The total energy contained in moving fluid is the sum of what three energies?
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Pressure
Kinetic (Velocity) Gravity (Hydrostatic Pressure) |
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What unit is pressure expressed in?
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mmHg (millimeters of Mercury)
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What is the primary form of energy used to move blood?
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Pressure (potential/stored) Energy
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What is the relationship between heart rate and blood volume?
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Directly Proportional
> rate = > volume < rate = < volume |
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What is the lesser form of energy used to move blood?
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Kinetic Energy (Velocity)
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What is the smallest form of energy used to move blood?
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Gravitational Energy
(Hydrostatic Pressure) |
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In a supine patient, what is the hydrostatic pressure at the ankles?
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0 mmHg
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In a standing patient, what is the hydrostatic pressure at the ankles?
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100 mmHg
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Define hydrostatic pressure (gravitational energy).
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The weight of the column of blood extending from the heart to the level where pressure is measured.
0 mmHg at heart level |
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What is needed to move blood from one point to another?
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Energy gradient
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What is the relationship between energy gradient and flow?
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Directly proportional
> gradient = > flow < gradient = < flow |
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The tendency of a fluid to resist changes in velocity is called what?
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Inertia
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As blood moves farther out to the periphery, how is its energy primarily dissipated?
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Heat
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What is the equation for calculating resistance?
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Resistance = 8 * viscosity * vessel length / pi * radius(4)
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What is the relationship between resistance and viscosity/vessel length?
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Directly proportional
> viscosity/vessel length = > resistance < viscosity/vessel length = < resistance |
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What is the relationship between resistance and the radius?
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Inversely Proportional
> radius = < resistance < radius = > resistance |
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What has the greatest effect on resistance: viscosity/vessel length or radius?
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Radius
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What is internal friction within a fluid called?
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Viscosity
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Why is energy dissipated as heat?
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Viscosity: RBCs rubbing against each other
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What effect does elevated hematocrit have on blood?
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Increased Viscosity
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What effect does severe anemia have on the blood?
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Decreased Viscosity
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What is the relationship between viscosity and velocity?
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Inversely Proportional
> viscosity = < velocity < viscosity = > velocity |
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Slower layers of flow close to vessel walls with faster flowing layers closer to the center of the vessel, is called what?
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Laminar (Stable) Flow
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Layers of flow moving at the same speed, is called what?
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Plug (Blunted) Flow
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Where is plug flow typically found?
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Vessel Origin (such as bifurcations)
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Increased friction between molecules and flow layers results in what kind of energy loss?
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Viscous Energy Loss (Viscosity)
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Deviations from laminar flow, due to changes in direction and/or velocity, results in what kind of energy loss?
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Inertial Energy Loss (Kinetic)
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What happens to laminar flow as it exits a stenosis?
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Flattened flow profile, disorganized flow
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Name the equation which defines the relationship between pressure, volume flow, and resistance (answering the question of how much fluid moves through a vessel).
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Poiseuille's Equation
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Describe Poiseuille's Equation (FULL)
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F = (P1-P2)*pi*R(4) / 8*N*L
F (Volume Flow) = P1 (Proximal mmHg) - P2 (Distal mmHg) * PI * R(4) (radius) / 8 * N (viscosity) * L (length) |
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Describe Poiseuille's Equation (SIMPLIFIED)
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F = P / R
F = Flow P = Pressure R = Resistance |
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In Poiseuille's Equation, what factor has the most dramatic effect on resistance?
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Diameter/Radius
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What is the relationship between vessel radius and volume flow?
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Directly Proportional
> radius = > flow < radius = < flow |
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Will a small change in radius have a small or large effect on volume flow?
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Large
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What equation defines the relationship between velocity and area?
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Law of Conservation of Mass
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Describe the Law of Conservation of Mass
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F = A * V
F = Volume Flow A = Area V = Velocity |
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What is the relationship between area and velocity?
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Inversely Proportional
> area = > velocity < area = < velocity |
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What unitless value predicts when fluid becomes unstable/disturbed?
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Reynolds Number = 2000
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This type of flow originates from a steady driving pressure and is described by Poiseuille's Equation.
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Steady Flow
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This type of flow originates from variable driving pressures and variable systemic response
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Pulsatile Flow
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What type of pulsatile flow occurs during systole?
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Antegrade
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What type of pulsatile flow occurs during late systole and early diastole?
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Retrograde (due to a negative pressure gradient and peripheral resistance reflecting the pressure wave proximally)
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What type of pulsatile flow occurs during late diastole?
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Antegrade
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Sudden closure of the aortic valve, causes a momentary elevated rebound in the pressure reading, such that the smooth downward slope of the pressure waveform is interrupted by a very brief upward movement. What is this called?
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Dicrotic Notch
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What kind of flow resistance is found when steady flow is present?
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Low Flow Resistance
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What kind of flow resistance is found when pulsatile flow is present?
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High Flow Resistance
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What doppler finding indicates low/high flow resistance?
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Biphasic = Low Flow Resistance
Triphasic = High Flow Resistance |
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Describe the appearance of Low Flow Resistance on doppler.
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Low Flow Resistance =
Biphasic = Fast antegrade flow Slow antegrade flow |
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Describe the appearance of High Flow Resistance on doppler.
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High Flow Resistance = Triphasic =
Antegrade flow Retrograde flow Antegrade flow |
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If stenosis is present in a high resistance flow vessel, how is this identified on doppler, distal to a significant stenosis?
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Since retrograde flow disappears downstream from the stenosis, the normally triphasic profile becomes a weaker biphasic profile.
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If stenosis is present in a high resistance flow vessel, how is this identified on doppler, proximal to a significant stenosis?
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Since retrograde flow disappears downstream from the stenosis, the normally triphasic profile becomes a strong biphasic profile.
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If stenosis is present in a high resistance flow vessel, how is this identified on doppler, immediately prior to a significant stenosis?
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Monophasic profile (due to blunted antegrade flow)
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What is the constriction/dilation relationship between arteries and arterioles?
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Inversely Proportional
Arteries constrict = Arterioles dilate Arteries dilate = Arterioles constrict |
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If periphery inflow pressure falls due to arterial stenosis upstream, what is the natural response of the periphery vessels?
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Vasodilation
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What two compensatory reactions can cause relatively normal blood flow even in the presence of significant arterial stenosis or occlusion?
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1. Collateral Network
2. Reduced peripheral resistance |
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Increased volume flow, retrograde flow, increased velocity, and waveform pulsatility changes indicate what?
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Presence of a collateral network
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What effect does exercise have on the peripherals?
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Causes vasodilation, which lowers peripheral resistance increasing peripheral blood flow
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What is the best single vasodilator of resistance vessels with muscle tissue?
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Exercise
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Besides exercise, what other system can cause peripheral vasoconstriction/vasodilation? Why?
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Sympathetic Nervous System, to control body temperature
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The ability of most vascular beds to maintain constant level of blood flow over a wide range of perfusion pressures is called what?
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Autoregulation
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If systemic BP rises, what happens to peripheral vessels?
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Vasoconstriction
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If systemic BP falls, what happens to peripheral vessels?
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Vasodilation
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Vigorous exercise (or significant stenosis) will produce what type of doppler flow pattern (resistance & # of phases) in extremity arteries? Why?
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Low Resistance Flow
Monophasic (a result of vasodilation) |
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Blood flow to a cool extremity will produce what type of doppler signals? Why?
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Pulsatile (due to sympathetic vasoconstriction)
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Blood flow to a warm extremity will produce what type of doppler signals? Why?
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Steady (due to sympathetic vasodilation)
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Pulsatility changes alone do not differentiate well between what two pathologies?
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Occlusion & Severe Stenosis
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Doppler waveforms may not be altered in the presence of pathology if these are present.
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Collaterals
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Distal effects of obstructive disease may only be detectable after what?
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Exercise/Stress
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A significant stenosis causes a noticeable reduction in what two factors?
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Volume Flow and Pressure
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A cross-sectional area reduction of 75% equals a diameter reduction of what?
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50% diameter reduction
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Describe the flow profile proximal to a stenosis.
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Dampened
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Describe the flow profile within the stenosis.
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Elevated velocity
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Describe the flow profile distal to a stenosis.
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Flow disturbances (eddies, vortices)
Retrograde flow Reduced velocities |
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Post stenosis, what effect do disturbed flow patterns (eddies, vortices) have on viscosity?
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Lower Viscosity
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