Instrumentation, Hemodynamics, and Doppler Flashcards
Tardus parvus indicates which of the following? A. Severe outflow disease B. Severe inflow disease C. Downstream arteriolar dilatation D. Showering emboli
B. Tardus parvus is the waveform appearance in which the systolic upstroke is delayed. This waveform is indicative of severe proximal, or inflow, disease.
The venous system contains what percent of all of the blood in the body? A. 20% to 30% B. 50% C. 60% to 70% D. 99%
C. The venous system holds approximately 66% of the blood in reserve at any one time.
With inspiration, which of the following is true?
A. Abdominal pressure increases and intrathoracic pressure decreases
B. Abdominal pressure decreases and intrathoracic pressure increases
C. Abdominal pressure increases and intrathoracic pressure increases
D. Abdominal pressure decreases and intrathoracic pressure decreases
A. With inspiration, the diaphragm moves inferior, compressing the IVC and causing increased abdominal pressure. At the same time, the intrathoracic pressure decreases, causing blood to be sucked into the thorax from the upper extremities and head.
As the blood vessel decreases in size, which of the following is true?
A. There is an increase in velocity and an increase in pressure
B. There is a decrease in velocity and a decrease in pressure
C. There is an increase in velocity and a decrease in pressure
D. There is a decrease in velocity and an increase in pressure
C. The continuity equation (Q=VA) indicates that where area decreases, velocity increases. According to Bernoulli, where velocity increases, pressure decreases.
Which of the following is true in the presence of a nonhemodynamically significant stenosis?
A. There is a corresponding pressure increase at the point of stenosis
B. There is a corresponding pressure decrease distal to the point of stenosis
C. There is a corresponding pressure increase proximal to the point of stenosis
D. There is a corresponding pressure decrease at the point of stenosis
D. Pressure decreases at the point of a stenosis. In a nonhemodynamically significant stenosis, the pressure returns to normal distal to a stenosis because the velocity decreases to the prestenotic velocity.
Monophasic flow in a resting lower extremity artery
A. Is indicative of normal flow
B. Is indicative of moderate to severe disease
C. Is normal if the patient is >60 years of age
D. Is normal with ABIs of 0.9 or greater
B. Phasicity of the arterial waveform indicates the resistiveness of the distal bed. In a resting lower extremity, the distal arterioles are high-resistance. Therefore, a high-resistance multiphasic waveform is expected. Monophasic flow indicates dilatation of the distal arterioles, indicative of moderate to severe disease.
Which of the following will increase the hemodynamic resistance? A. Decrease the viscosity of the blood B. Increase volumetric flow rate C. Decrease the vessel length D. Increase vessel length
D. If resistance increases, flow decreases. Resistance is caused by a decrease in vessel radius, an increase in vessel length, or an increase in viscosity.
With laminar flow in a straight vessel, what part of the flow is said to be the fastest?
A. The center of the stream
B. At the boundary layer
C. Velocities are the same across the stream
D. Toward the edges
A. In laminar flow, blood travels fastest in the center of the vessel, and becomes progressively slower as it nears the edges.
In the venous circulation, which of the following is the only variable of hydrostatic pressure? A. Height B. Gravity C. Density D. Viscosity
A. In the venous system, height, or distance from the heart, is the only variable in the equation.
Which of the following occurs with deep inspiration?
A. There is an increase in blood flow from the lower extremities to the right heart
B. There is an increase in blood flow from the upper extremities and head to the right heart
C. There is a decrease in subdiaphragmatic pressures
D. There is an increase in pressure in the thorax
B. With deep inspiration, there is increased flow from the upper extremities and head as a result of decreased pressure in the chest.
A delay in the systolic upstroke is termed A. Monophasic flow B. Laminar flow C. Turbulence D. Tardus parvus
D. Tardus parvus is a sloped, or delayed systolic upstroke as a result of proximal arterial disease. Healthy arteries should have a sharp systolic upstroke.
According to Poiseuille's law, an increase in the pressure difference causes A. A decrease in flow B. An increase in viscosity C. An increase in flow D. An increase in resistance
C. Poiseuille’s law relates flow to changes in pressure, the radius of the vessel, the length of the vessel, and viscosity of the blood. As the pressure difference (i.e., gradient) increases, flow increases.
Which of the following will have the greatest impact on resistance in a vessel? A. Viscosity B. Pressure difference C. Vessel length D. Vessel radius
D. In Poiseuille’s law, the radius component is to the fourth power. Therefore, changes in radius will have a dramatic impact in flow.
If the radius of a blood vessel is halved, what is the corresponding change in flow?
A. The flow is one-fourth of what it was before the narrowing
B. The flow is one-half of what it was before the narrowing
C. Blood flow is decreased by a factor of 16
D. Blood flow is decreased by a factor of 20
C. In Poiseuille’s law, the radius component is to the fourth power. A change in radius by one-half is equivalent to a 16-fold decrease in flow.
What effect does increasing vessel length have on flow?
A. The longer the vessel, the more flow there is
B. The longer the vessel, the lower the flow
C. The longer the vessel, the fewer the frictional losses
D. The longer the vessel, the less resistance there is
B. Length is directly related to resistance. The longer a vessel, the more resistance there is due to frictional losses, and therefore, decreased flow.
According to Bernoulli,
A. There is no relationship between pressure and velocity
B. Velocity increases as pressure increases
C. Pressure and velocity are inversely related to each other
D. Velocity and pressure are directly related to each other
C. Bernoulli’s principle states that pressure and velocity have an inverse relationship as part of the law of conservation of energy.
What type of flow is commonly seen at the entrance of large vessels? A. Laminar B. Parabolic C. Chaotic D. Plug
D. Plug flow, which resembles a flat wave front before the flow assumes a more parabolic shape, is typically seen in the proximal aorta and at the entrance of large vessels.
What waveform is monophasic with a large amount of diastolic flow consistent with? A. A distal low-resistance bed B. A distal high-resistance bed C. A multiphasic waveform D. Turbulent flow
A. Monophasic with a large amount of diastolic flow is indicative of a distal low-resistance bed.
What is the type of flow most commonly seen in vessels in the body? A. Laminar B. Turbulent C. Plug D. Stenotic
A. Laminar flow is considered to be the predominant type of flow present within the blood vessels of the body. In laminar flow, blood is fastest in the center, with flow slowing progressively toward the vessels’ walls.
When tardus parvus is present, it indicates
A. Mild disease more distally
B. Normal flow
C. Disease proximal to the point of sampling
D. Severe disease distal to the point of sampling
C. Tardus parvus is a delayed systolic upstroke consistent with proximal arterial disease. The normal arterial waveform has a sharp upstroke.
Which of the following increases as vessel area decreases? A. Pressure B. Velocity C. Flow D. Cardiac output
B. According to the continuity equation(Q=VA), velocity increases where area decreases.
The stationary red blood cells along the vessel walls are called the A. Viscosity layer B. Boundary layer C. Friction layer D. Cellular layer
B. The boundary layer is a stationary layer of red blood cells (RBCs) adjacent to the vessel wall. RBCs progressively increase in velocity until the fastest flow in the center of the vessel is reached.
Distal to a nonhemodynamically significant stenosis
A. The velocity decreases and the pressure increases
B. The velocity and pressure decrease
C. There is a pressure drop
D. The velocity increases and the pressure decreases
A. Distal to a nonhemodynamically significant (or “critical”) stenosis, the velocity decreases (i.e., returns to normal), and there is a corresponding pressure increase consistent with Bernoulli’s principle.
Ohm's law is analogous to Poiseuille's law, where current is represented by A. Flow B. Resistance C. Pressure difference D. Gravity
A. Ohm’s law is analogous to Poiseuille’s law. Pressure is represented by voltage, flow is current, and resistance is the same for both.
Increasing resistance has what effect on flow?
A. Flow is increased with an increase in resistance
B. Flow is decreased with an increase in resistance
C. Flow and resistance are unrelated
D. There are too many other variables to tell
B. Poiseuille’s law states that flow is inversely proportional to resistance. As resistance increases, flow decreases.
In which blood vessels do nutrient and waste exchange occur? A. Arterioles B. Capillaries C. Venules D. Arteries
B. Capillaries are the microscopic vessels connecting arterioles and venules, and are the location for nutrient/waste exchange.
Which of the following is true about hydrostatic pressure?
A. In a supine patient the hydrostatic pressure is greater at the ankles than at the heart
B. In a standing patient, with arm raised over head, the arm has a positive hydrostatic pressure
C. In a completely supine patient, the hydrostatic pressure is zero across all levels
D. In a standing patient, the hydrostatic pressure at the heart is 100 mm Hg
C. Hydrostatic pressure is based on vertical distance from the heart (the effect of height in the equation). When supine, everything is the same level as the heart, so the hydrostatic pressure is zero. When standing, anything below the heart is a positive hydrostatic pressure and anything above the level of the heart is negative hydrostatic pressure.
Which of the following can be predicted by Poiseuille's law? A. Volume flow in a tube B. Flow velocities in a tube C. Pulsatility in arteries D. Turbulence distal to a stenosis
A. Poiseuille’s law predicts volume flow (Q) when the radius and length of the vessel, viscosity of the blood, and pressure gradient are known.
A 50% reduction in the radius of a blood vessel results in what factor of energy loss? A. 2x B. 5x C. 16x D. 25x
C. In Poiseuille’s law, volume flow is proportional to the radius to the fourth power. A 50% reduction, or halving, of the radius results in a decrease in flow of 16x.
A 50% reduction in diameter is equal to what percent reduction in area? A. 10% B. 25% C. 50% D. 75%
D. A 50% reduction in diameter results in a 75% reduction in area.
Why is blood slowest in the capillaries?
A. To permit maximum exchange of nutrients and wastes
B. To be slow enough to enter the venules
C. Due to increased right heart pressures
D. Due to decreased left heart pressures
A. Capillaries are about the same size as red blood cells (RBCs). The friction caused by the RBCs touching the vessel walls causes the cells to move very slowing, permitting maximum exchange of nutrients and wastes.
Spectral broadening is A. An abnormal flow pattern B. Common in tortuous vessels C. Unusual in the carotid bulb D. Never seen with CW Doppler
B. Spectral broadening is seen whenever may flow velocities are present in a sample volume. Spectral broadening is common with the use of large spectral gates and CW Doppler, and also in the presence of turbulence, which may be a result of stenosis, areas of vessel dilatation, and tortuous vessels. Spectral broadening will also be seen if the spectral gain is too high.
Red blood cells increase scatter by 16 times if the frequency is doubled because they are A. Weak reflectors B. Raynaud's scatterers C. Rayleigh scatterers D. Specular reflectors
C. Rayleigh scatterers are very small reflectors compared to the wavelength of the beam. Red blood cells, which are a type of Rayleigh scatterer, scatter to the fourth power of the frequency, so a doubling of frequency causes 16x more scatter. Scatter is a type of attenuation because the sound energy is directed into all directions, leaving less energy to be transmitted through the tissue.
Which of the following is representative of normal lower extremity peripheral venous flow? A. Pulsatile flow B. Respiratory phasicity C. High transmural pressure D. Nonspontaneous flow
B. Lower extremity peripheral venous flow should be spontaneous, have respiratory phasicity, be noncontinuous, and be nonpulsatile. Veins typically have low transmural pressure, and will appear elliptical when supine due to the increased pressure outside the vessel compared to the pressure inside the vessel.
In order to eliminate mirror image artifact, which of the following techniques can be employed? A. Increase angle closer to 90 degrees B. Increase color or spectral gain C. Increase acoustic power D. Reduce angle to flow
D. Mirror-image artifact occurs when there is a close to 90-degree angle to flow, or when the color/spectral gain is too high.
The spectral waveform is too dark. Which of the following would be the best method to improve the image? A. Increase the output power B. Increase the spectral gain C. Decrease the spectral gain D. Increase the PRF
B. Spectral gain is the control that makes the spectral waveform brighter or darker. Increase the spectral gain if the spectral signal is too dark, but be careful not to increase the spectral gain too much.
A sonographer switches to a higher frequency transducer. What effect will that have on aliasing?
A. Increased risk of aliasing
B. Decreased risk of aliasing
C. Aliasing will definitely not occur
D. Transducer frequency does not affect aliasing
A. Frequency shift is directly proportional to operating frequency. The higher the frequency shift, the greater the risk for aliasing. Aliasing occurs when the frequency shift exceeds the Nyquist limit, equal to one-half of the PRF.
Which of the following will reduce the risk of aliasing? A. Increase the depth B. Decrease the PRF C. Increase the Doppler angle D. Lower the scale
C. In the Doppler equation, frequency shift is directly proportional to the cosine of the Doppler angle. Increasing the angle causes the cosine of the angle to decrease, resulting in a lower frequency shift. Decreasing the frequency shift reduces the risk of aliasing.
All of the following are components of the Doppler shift equation except for A. Frequency B. Spatial pulse length C. Doppler angle D. Propagation speed
B. The Doppler equation includes everything listed except spatial pulse length. In addition to frequency, Doppler angle, and propagation speed, the Doppler equation also includes frequency shift and velocity of the blood.
