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66 terms

HEMODYNAMICS

STUDY
PLAY
-The Doppler Effect is explained by a change in ____ due to ____ of the ____ or ____
-There is also a change in ____
-frequency, motion, sound source, reflector
-wavelength
-A reflector moving towards the source leads to an ____ in frequency
-A reflector moving away from the source leads to a ____ in frequency
-increase (positive shift)
-decrease (negative shift)
Doppler shift is the difference between?
the frequency going into the body and the frequency returned to the transducer
Blood Flow:
-blood is composed of? (4)
-blood is about ___% cells
-plasma, erythrocytes, leukocytes, and platelets
-40 (hematocrit)
-If your hematocrit is too low what will happen? (hypovolemia)
-If your hematocrit is too high what will happen? (hypervolemia)
-bleed
-clot
Fluid Characteristics: Density is
Mass per unit volume
--Mass: An object's resistance to acceleration
Fluid Characteristics: Viscosity is
resistance to flow
Fluid Characteristics: Inertia is
resistance to acceleration
The more mass/vol (density) the more
inertia
Fluid Characteristics: Pressure is
force per unit area
Fluid Characteristics: Pressure
-pressure is Equally exerted in all directions in a ____ fluid (omnidirectional)
-A pressure difference is required for
-Increased pressure difference, ____flow rate
-Flow travels from the ____ to the ____ pressure-end
-static
-flow to occur
-increased
-higher, lower
Volume Flow Rate is the
-measured in
-determined by
Volume of blood that passes a given point per unit time
-mL/m (or s)
-pressure difference and resistance to flow (If resistance increases, volume flow rate decreases)
Volume Flow Rate:
-Flow resistance is determined by
-the formula is
-Poiselle's Law (or a variant of it)
-FR = 8 X Length X viscosity/ p X r^4
Volume Flow Rate:
-Flow rate is determined by
-flow rate depends on what 4 things?
-Poiselle's Law
-pressure difference, vessel length, vessel diameter and fluid viscosity
Poiselle's law tells us that the amount of blood is...
constant
Poiselle's Law Equation
Q = π p r^4/8 l n
Poiseuille's Law:
Q = Quantity of blood
π = constant (3.14)
p = pressure difference
r = vessels radius
l = vessel length
n = blood viscosity
-Quantity of blood
-constant (3.14)
-pressure difference
-vessels radius
-vessel length
-blood viscosity
Flow is regulated by
pressure and vessel size variations
What is the most important factor in determining volume flow rate?
vessel radius
Flow Resistance Relationships:
-Increase tube length, ____ resistance
-Increase viscosity, ____ resistance
-Increase tube (vessel radius), ____ flow resistance
-increase
-increase
-decrease
Flow Rate Relationships:
-Increase pressure difference, ____ flow rate
-Increase diameter, ____ flow rate
-Increase vessel length, ____ flow rate
-Increase viscosity, _____ flow rate
-increase
-increase
-decrease
-decrease
Types of blood flow (5)
-Plug
-Laminar
-Parabolic
-Disturbed
-Turbulent
Laminar flow: Where is blood flow faster and slower?
faster in the center, slower away from center
Parabolic flow:
perfect laminar flow
Plug flow: where is blood flow faster and slower?
very slow at the walls, but still faster in the center
Blood Flow: Shape depends
-small and medium vessels produce a ____ shape.
-larger vessels produce a ____ or ____ flow shape.
vessel size
-parabolic
-plug or blunted flow- fairly constant flow speed across vessel
Laminar Blood Flow:
-Occurs in a ____ substance
-____ substance
-non uniform flow velocities fastest in
-fluid
-viscous
-center of vessel
Laminar Blood Flow:
-non uniform flow velocities with flow faster in the center of vessel occurs due to
-viscous drag
-friction
Parabolic Blood Flow:
-Steady, laminar flow in a ___ & ___ tube
-Does or doesn't occur very often in the body? Because?
-long and straight
-doesn't because vessels are not long enough
What blood flow is seen commonly in the body?
non parabolic laminar blood flow
Average blood flow speed=
½ maximum flow speed (at center of vessel)
Disturbed Flow:
-____ streamlines are altered
-Occurs at ____ or ____
-Flow is still in the ____ direction
-A type of ____
-Is disturbed flow an indicator of pathology?
-parallel
-bifircations or stenosis
-forward
-laminar
-not nessecarily
Turbulent Flow:
-The direction of this flow is
-circular flow is called
-where would you see turbulant flow?
-in many directions (chaotic and random), but remains forward overall
-eddie currents
-distal to Dx
Turbulent Flow:
-The flow speed at which turbulent flow occurs is determined by the ____
--which is dependent upon ____ and ____ of fluid and ____ of tube
-Reynolds number
-density, viscosity, diameter
Sounds caused by turbulance, heard with a stethoscope are called
bruits
Reynold's Number:
-formula?
-A reynold's number above ____ indicates turbulence
-R = average flow speed X tube diameter X density/viscosity
-2000 (Critical reynold's number)
Compliance
-arterial walls are ____
-measured with ___
-elastic
-PI
Pulsatility:
-is the ability of a structure to
-depends upon
-allows for
-expand and contract
-stroke volume, ventricular ejection time, peripheral resistance and vascular compliance
-flow reversal
The Continuity Rule:
-states that volume flow rate remains
-the continuity rule =
-if vessel lumen is decreased, flow speed at areas of stenosis will ____
-constant throughout a vessel
-average flow speed X cross sectional area of the vessel
-increase
The Continuity Rule:
-Expressed with a variant of Poiselle's Law:
-Doppler shift is directly related to
-Average flow speed = Pressure difference X diameter2/ 32 X Length X viscosity
-flow speed
Poiselle's Law vs. The Continuity Equation:
-Poiselle's Law: deals only with ____
-which means no ____
-as diameter decreases, flow speed ____
-long straight vessels
-stenosis
-decreases
Poiselle's Law vs. The Continuity Equation:
-Continuity Rule: describes a
-as diameter decreases, flow speed ____
-short (stenotic) region of a vessel
-increases
Bernoulli's Equation:
-All KE, PE and work are ____
-Energy is lost through ____
-conserved
-friction (changed to heat (inertial loss))
***p + rgh + 1/2 rv2 = B
Bernoulli's Equation:
-Pressure at a region of stenosis is less than
-As flow energy increases, pressure energy ____
-A drop in pressure associated with high flow speeds at a ____
-proximal or distal to that region
-decreases
-stenosis
Bernoulli's Equation:
-formula
-P1 - P2 = 4 V2
--Pressure Drop = ½ X density X (flow speed )^2
Arterial vs. Venous Flow:
Pulsatility vs. Respiratory Changes
-Arteries have a higher or lower pressure than veins?
-wall composition
-higher
-Internal Elastic Lamina, External Elastic Lamina
Hemodynamics:
-Intravascular Pressure
-Cardiac Output
-heart contraction
static filling
hydrostatic pressure
-volume per minute
Venous Flow:
-are veins more muscular or elastic?
-As resistance in peripheral arteries increased venous return ____
-Vary with ____ and show ____ changes
-larger veins will have ____
-muscular
-decreases
-pressure, respiratory
-valves
Flow Variations:
-Normal flow is considered
-As lumen size increases you can what kind of flow?
-Also as lumen size increases, you can get varied flow patterns (3)
-laminar
-plug flow (more uniform velocities)
-eddy flow
high velocity flow
stagnant flow
Flow Variations:
-As vessels turn the velocities will be higher where?
at the outer edges of the vessel
Resistive Index:
-the resistance of the distal ____ ____ to fill with blood
-RI=
-anything less than ___ is low resistance, and anything above ___ is high
-capillary bed
-Ps - Ed/ Ps
-0.7, 0.7
Resistance:
-the less capillaries available, the ____ resistance and the ____ the RI
-high resistance signals lack ____ flow or have ____ diastolic flow
-more, higher
-diastolic, reverse
High resistive index diastole will touch or cross the
baseline
Flow Variations:
-As vessels near critical stenosis you may see ____ ____
--filling in of the ____ ____
--velocities are increased or decreased?
-spectral broadening
--systolic window
-increased
Flow Variations: As vessels stenoes
-effects vary with degree of ____ and normal vessel ____
-effects do not affect hemodynamics until about ___% stenosis
-If a vessel started as low resistance generally the vessel loses ____ flow as pathology worsens
-stenosis, characteristics
-60
-diastolic
Flow Variations:
High resistance signals tend to lose ____ as pathology increases
phasicity
Pulsatility:
-applies to ____ only
-describes the amount of ____ of walls
-PI=
-arteries
-elasticity
-Ps - Ed / mean velocity
The Doppler Effect:
-Changes in relative motion are seen as changes in ____
-Scanning angle should be as ____ to vessel as possible
-FREQUENCY
-parallel
The Doppler Effect:
-The Fd =
-the frequency difference is measured in ___ and the inital and returned frequency are measured in ___
-F r - F i
-KHz, MHz
The Doppler Effect:
-The frequency difference is in KHz because sound is shifted to
audible sound
The Doppler Equation:
-Fd =
or
-V(scatter speed)=
-2 FoV cos θ / C
-77 Fd/Fo cos θ
The Doppler Equation: Relationships
-Increase Fd, ____ scatter speed
-Increase Fo, ____ scatter speed
-Increase Cos, ____ scatter speed
-increase
-decrease
-decrease
The Doppler Equation:
-As angle goes up the cos of the angle goes
-Cos 90 =
-Cos 0 =
-Increase Doppler angle, ____ scatter speed
-down
-0
-1
-increase
Doppler Ultrasound:
-Increase Fo, ____ detectable Fd
-increase
Doppler Ultrasound:
-Set angle between ____ degrees
-Largest Doppler return at ___ degrees
(Cannot determine forward vs. reverse flow)
-No Doppler return at ___degrees
-30-60
-0
-90
Other Doppler Applications: Radar and motion detectors
-Use ____ frequencies
-Approximately ___ kHz
-lower
-25