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Understanding Ultrasound Physics/Edelman Ch 18
Understanding Ultrasound Physics
78
Medical
09/27/2010

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Term
Hemodynamics
Definition
The study of blood moving through the circulatory system
Term
Any volume divided by time
(L/min, ml/s, etc)
Definition
Flow is reported in what units?
Term
Flow
Volume Flow Rate
Definition
This indicates the volume off blood moving during a particular time; it answers the question, "How much?"
Term
Velocity
Definition
This indicates the speed of a fluid moving from one location to another; it answers the question, "How fast?"
Term
Any distance divided by time
(cm/s, m/min, etc)
Definition
Velocity is reported in what units?
Term
Flow
Definition
The following are forms of what?
- pulsatile
- phasic
- steady
Term
Pulsatile Flow
Definition
This occurs when blood moves with variable velocity resulting from cardiac contraction (ex: arterial circulation)
Term
Phasic Flow
Definition
This occurs when blood moves with a variable velocity resulting from respiration (ex: venous circulation)
Term
Steady Flow
Definition
This occurs when blood moves at a constant velocity (ex: venous circulation when breathing stops for a moment)
Term
Laminar Flow
Definition
What kind of flow exists when flows are aligned and parallel
Term
Laminar Flow
Definition
The following are two forms of what?
- Plug Flow
- Parabolic Flow
Term
Plug Flow
Definition
This type of laminar flow occurs when all of the layers and blood cells travel at the same velocity
Term
Parabolic Flow
Definition
This type of laminar flow occurs when velocity is highest in the center of the lumen and weakest at the vessel wall
Term
Is plug flow and parabolic flow a normal finding?
Definition
Yes
Term
Turbulent Flow
Definition
What kind of flow exists when chaotic flow pattern - in many directions and many velocities - are present?
Term
Turbulant Flow converts flow energy into other energy forms such as ___ and ___
Definition
Sound & Vibration
Term
Sound associated with turbulent flow is called a ___
Definition
Bruit
Murmur
Term
Vibrations associated with a turbulent flow is called a ___
Definition
Thrill
Palpable Murmur
Term
Energy Gradient
Definition
Blood flows when the total fluid energy at one location differs from the total fluid energy at another location. What is this difference in energy called?
Term
Which statement is more precise?blood flows due to a pressure gradient or blood flows due to an energy gradient
Definition
Blood flows due to an energy gradient
Term
The following are forms of what?
- kinetic
- pressure
- gravitational
Definition
Energy
Term
Kinetic Energy
Definition
This form of energy is associated with a moving object. It is determined by the object's mass and it's speed
Term
Pressure Energy
Definition
This form of energy is a form of stored or potential energy, which has the ability to perform work
Term
Gravitational Energy
Definition
This form of energy is a form of stored or potential energy that is associated with any elevated object.
Term
How is energy imparted to blood?
Definition
LV contraction during systole
Term
As blood flows throughout the body, name three ways its energy is lost
Definition
1. Viscous Loss
2. Frictional Loss
3. Inertial Loss
Term
Viscosity
Definition
This describes the thickness of a fluid
Term
High Viscosity
Definition
More energy is lost with the movement of (high or low?) viscosity fluids.
Term
Hematocrit
Definition
The percentage of red blood cells (and other cellular matter) in the blood is called what?
Term
What is the normal hematocrit level?
Definition
45%
Term
What happens to blood viscosity if the hematocrit level drops (anemia)?
Definition
With lower hematocrit levels, blood has reduced viscosity
Term
Frictional Energy Loss
Definition
This form of energy loss occurs when flow energy is converted to heat as one object rubs against another
Term
Viscous Energy Loss
Definition
This form of energy loss occurs when blood overcomes its own internal stickiness
Term
Inertial Energy Loss
Definition
This form of energy loss occurs when the speed of a fluid changes (regardless of whether it accelerates or decelerates)
Term
Inertial Energy Loss
Definition
What form of energy loss occurs at these three events:
- pulsatile flow
- phasic flow
- stenosis
Term
In a stenotic vessel, where does maximal velocity occur?
Definition
At the vessel's narrowest point
Term
In a stenotic vessel, where does reduced velocity occur?
Definition
Beyond the vessel's narrowest point
Term
A narrowing in the lumen of a blood vessel is called what?
Definition
Stenosis
Term
How does stenosis effect flow direction?
Definition
Flow direction can change (turbulence) as blood flows through the narrowing
Term
How does stenosis effect flow velocity?
Definition
Velocity increases flowing into the narrowing and decreases past the narrowing
Term
How does stenosis effect pressure?
Definition
Increased pressure at the narrowing, decreased pressure past the narrowing (pressure gradient)
Term
How does stenosis effect flow pattern (pulsatile, phasic, steady)?
Definition
Pulsatile flow pattern converts to a steady flow pattern
Term
With a flow OR resistence increase, what will happen to pressure gradient?
Definition
Pressure Gradient Increase
Term
With a pressure gradient increase OR a resistance decrease, what will happen to flow?
Definition
Flow Decrease
Term
The ___ the pressure difference, the ___ the flow rate
Definition
Greater
Term
What is the formula for calculating pressure gradient?
Definition
PG = Flow x Resistance
Term
The pressure gradient formula is similar to what other formula?
Definition
Ohm's Law
(voltage = current x resistance)
Term
Vein walls are (thick|thin) and (collapsible|noncollapsible)
Definition
Thin
Collapsible
Term
During normal function, veins are (high|low) pressure and (fully|partially) filled
Definition
Low
Partially
Term
The cross-sectional shape of a vein during normal function is ___
Definition
Flattened & Hourglass Shaped
Term
Are veins typically low or high resistance vessels?
Definition
Low Resistance (like arteries)
Term
How can veins handle a large volume increase without a similar increase in pressure?
Definition
Cross-sectional shape can increase to oval and then circle
Term
Normal veins increase flow to the heart with a (large|small) increase in pressure
Definition
Small
Term
The shape and volume of veins are determined by the pressure acting to expand them. What is this pressure called?
Definition
Transmural Pressure
Term
After what point do venous pressures attain their highest levels?
Definition
After veins are stretched to their maximum dimension
Term
Hydrostatic Pressure
Definition
The weight of blood pressing on a vessel measured at a height above or below heart level
Term
Hydrostatic pressure is reported in what units?
Definition
mmHg
Term
Blood pressure is accurately assessed when taken where?
Definition
At the level of the heart
Term
When blood pressure is taken above or below the level of the heart, ___ pressure introduces ___ into the measurement
Definition
Hydrostatic Pressure
Error
Term
When blood pressure is taken above the level of the heart, the measurement is too (high|low) due to ___
Definition
Low
Hydrostatic Pressure
Term
When blood pressure is taken below the level of the heart, the measurement is too (high|low) due to ___
Definition
High
Hydrostatic Pressure
Term
What is the hydrostatic pressure of a patient in the supine position?
Definition
0 mmHg
Term
Is a blood pressure measured anywhere on a supine patient accurate?
Definition
Yes
Term
A supine patient's arterial BP (measured at the arm) is 140 mmHg. What is the hydrostatic pressure at all locations within the arterial circulation?
Definition
0 mmHg
Term
140 mmHg
Definition
A supine patient's arterial BP (measured at the arm) is 140 mmHg. What is the arterial pressure at their knee?
Term
A supine patient's arterial BP (measured at the arm) is 140 mmHg. What is the arterial pressure in their carotid artery?
Definition
140 mmHg
Term
In a standing patient, where are negative hydrostatic pressures found? Positive hydrostatic pressures?
Definition
- Above the level of the heart
+ Below the level of the heart
Term
Measured BP is a combination of what two other measurable pressures?
Definition
Circulatory Pressure + Hydrostatic Pressure
Term
Downward movement of the diaphragm occurs during what portion of the respiration process?
Definition
Inspiration
Term
Upward movement of the diaphragm occurs during what portion of the respiration process?
Definition
Expiration
Term
What occurs to thoracic blood pressure and blood flow during inspiration?
Definition
1. Thoracic pressure decreases
2. Thoracic venous flow increases
Term
What occurs to thoracic blood pressure and blood flow during expiration?
Definition
1. Thoracic pressure increases
2. Thoracic venous flow decreaese
Term
What occurs to lower body blood pressure and blood flow during inspiration?
Definition
1. Lower body pressure increases
2. Lower body venous flow decreases
Term
What occurs to lower body blood pressure and blood flow during expiration?
Definition
1. Lower body pressure decreases
2. Lower body venous flow increases
Term
What happens to venous flow in the legs during inspiration?
Definition
Decreases
Term
All of the following occur during expiration except:
A. venous return to the heart decreases
B. venous flow in the legs increases
C. abdominal pressure increases
D. diaphragm rises into the thoracic cavity
Definition
C. abdominal pressure increases
Term
When venous flow in the leg decreases, venous return to the heart ___
Definition
Increases
Term
When venous flow in the leg increases, venous return to the heart ___
Definition
Decreases