# Shared Flashcard Set

## Details

100
Exam 2
57
Physics
Professional
11/08/2011

Term
 Define "velocity"
Definition
 speed (distance over time)
Term
 What are the SI units for velocity?
Definition
 m/sec
Term
 What are the CGS units for velocity?
Definition
 cm/sec
Term
 What are the British units for velocity?
Definition
 ft/sec
Term
 Which units of velocity are used for echocardiograhy?
Definition
 SI: m/sec
Term
 Which units of velocity are used for vascular?
Definition
 CGS: cm/sec
Term
 What is the equation that defines the relationship among flow, velocity, and area?
Definition
 Q=A•V
Term
 If the area of the aorta is 3.3 cm², what is the diameter? (How do you obtain the diameter?)
Definition
 D = 2√(A/π)D = 2√(3.3/π) = 2.05 cm
Term
 If the diameter of the aorta is 2.05 cm, what is the area? (How do you obtain the area?)
Definition
 A = D²•0.785A = 2.05²•0.7853.3 cm²
Term
 If the velocity is 33 cm/sec, and the flow is 4.4 L/min, what is the diameter of the aorta? (How do you obtain the diameter?)
Definition
 A=Q/VFirst, convert Q to cm³/sec4.4 L/min(1000/60) = 73.33 cm³/secA=73.33/33A=2.22 cm²
Term
 If the area of the aorta is 2.7 cm², and the flow is 5.1 L/min, and the aorta branches in arteries totaling 50 cm², what is the velocity in each branch artery? (How do you obtain the velocity?)
Definition
 V=Q/Total CSA of branchesFirst, convert Q to cm³/sec5.1 L/min(1000/60) = 85 cm³/secV=85/50 = 1.7 cm/sec*The area of the aorta is insignificant information
Term
 What is the first branch off the aorta not including the coronary arteries.
Definition
 Brachiocephalic (Innominate) Artery
Term
 The velocity of blood flow in the LVOT is 88 cm/sec, and the area of the LVOT is 7.7 cm², and the velocity in the aortic valve is 4.4 m/sec. What is the valve area? (How do you obtain the area?)
Definition
 V1A1=V2A2 in this case: (V1A1)/V2 But first convert V2 to cm/sec: 4.4 m/sec • 100 = 440 cm/sec A2 = (88•7.7)/440 = 1.54 cm2
Term
 Define "laminar" blood flow
Definition
 Blood flowing in orderly, undisturbed, concentric layers.
Term
 What are the two basic velocity profiles? Where and when do they occur?
Definition
 Plug and parabolic.Plug profile occurs during acceleration in systole in larger vessles and at stenoses and branches.Parabolic profile occurs during diastole in larger vessels and throughout the smaller vessles all the time.
Term
 Describe parabolic flow profile
Definition
 Velocity is highest in the center, dropping off toward wall. Peak velocity is twice the mean velocity. Velocity at walls is theoretically zero.
Term
 Describe plug flow profile
Definition
 Velocities are the same almost all the way across the lumen. Wall drag still slows down the outer layers.
Term
 Define "turbulence" and what noises might it cause in the body?
Definition
 Chaotic and disorderly flow. In cardiac studies, turbulence is called a "murmur" and called a "brooie" in vascular studies.
Term
 What are the variables that influence the likelihood of turbulence?
Definition
 If V=velocity, d=diameter or ρ=density is increased, or η=viscosity is decreased, the likelihood of turbulence will increase.
Term
 Give the equation that predicts the likelihood of turbulence and who developed it?
Definition
 The Reynolds number equation:Re=Vρd/ηV=velocity, d=diameter, ρ=density, η=viscosityA Reynolds number >2000 predicts turbulence
Term
 What is the effect on the likelihood of turbulence with a tripling of viscosity?
Definition
 The likelihood of turbulence will decrease 1/3.
Term
 When might a cardiac murmur be normal?
Definition
 During systole
Term
 When is a cardiac murmur never normal?
Definition
 During diastole
Term
 Define "viscosity"
Definition
 An internal friction created by molecular attraction, creating a tendency to resist motion.
Term
 What degree of stenosis must be reached in most arteries to be critical?
Definition
 70% or greater
Term
 How is "critial stenosis" defined?
Definition
 A sudden reduction in flow and blood pressure.
Term
 What is the the behavior of blood flow before, within, and distal to the hemodynamically significant stenosis?
Definition
 There is no noticable change in blood flow, but within the stenosis, the velocity increase due to the narrowing of the vessel. Once the flow is distal to the stenosis, turbulence ensues.
Term
 What happens to pressure within a stenosis and why?
Definition
 There is a reduction in pressure due to the Bernoulli effect which states, "As the speed of a moving fluid increases, the pressure within the fluid decreases."
Term
 If velocity through a mitral valve is 410 cm/sec, what is the pressure gradient across the valve?
Definition
 P1-P2 = 4(V2) First, convert cm to m 410 cm/sec • 100 = 4.1 m/sec ΔP = 4(4.12) = 67 mmHg
Term
 What is the most common complication resulting from atherosclerotic diease in the coronary arteries?
Definition
 Myocardial Infarction
Term
 What is the most common complication resulting from atherosclerotic diease in the carotid arteries?
Definition
 Ischemic Stroke
Term
 What is almost always the first symptom of lower extremity PAD?
Definition
 Pain with exercise, relief with rest.
Term
 What is an aneurysm and possible causes?
Definition
 Weakening and bulging of the cardiac or arterial wall. Can be due to infarcted tissue, atherosclerotic degeneration, infection, or congenital weakness.
Term
 What is the formula for the Law of LaPlace? Define the variables. Explain its significance in the vascular system.
Definition
 T∝P•dWall tention (T) is proportional to (∝) pressure (P) multiplied by diameter(d). The larger the vessel's diameter, the more tension is required to sustain a given pressure. In the body, the mean pressure doesn't change much--it's the diameter that changes as the wall weakens, requiring more wall tension to hold things together.
Term
 What are the units for wall tention?
Definition
 dynes/cm
Term
 What happens to wall tension if the diameter is tripled?
Definition
 T∝P•dIt increases
Term
 What is usually found on the wall of an aneurysm?
Definition
 A thrombus
Term
 What are the two basic functions of the venous part of the circulatory system?
Definition
 To return blood back to the heart and venous resevior.
Term
 What are the two possible useful functions of the venous reservor?
Definition
 To provide increased flow during exercise and provide volume to the core circulation in the event of severe hemorrhage.
Term
 What is compliance?
Definition
 The ability to expand and contgain more volume with little pressure increase.
Term
 What makes veins compliant?
Definition
 Veins are compliant because of normally semi-collapsed state.
Term
 What makes arteries compliant?
Definition
 Elastin
Term
 What are the physical characteristics of veins compared to arteries.
Definition
 Roughly half the wall thickness than arteries. Veins contain less elastin and smooth muscle in the media comparted to arteries.
Term
 Define "hydrostatic pressure"
Definition
 Force of gravity acting on a column of fluid.
Term
 How much hydrostatic pressure is possible in an average person standing still for a long time?
Definition
 90 mmHg
Term
 What structures help prevent hydrostatic pressure from happening?
Definition
 Venous valves and calf muscle.
Term
 What are the 5 mechanisms that help with venous return to the heart?
Definition
 1. Venous valves2. Skeletal muscle pump3. Respiratory pump4. Cardiac suction effect5. Vasomotor tone
Term
 What are the 3 types of venous structures in the lower extremities, and how do they function?
Definition
 Flow moves from (1) superficial veins to (2) deep veins via (3) perforating veins.
Term
Definition
 1. Stasis2. Hypercoagulability 3. Vessel wall injury
Term
 How is LE DVT thought to form?
Definition
 DVT is thought to originate often in two places from stasis:1. Muscular veins in calf 2. Behind valve leaflets
Term
 What is the most serious complication of DVT?
Definition
 Pulmonary Embolism
Term
 What are the two basic types of testing for DVT?
Definition
 1. Venous outflow plethysmography2. Ultrasound
Term
 How is venous imaging performed?
Definition
 Ultrasound
Term
 What demostrates patency of the vein?
Definition
 Compress veins with ultrasound probe to provoke reflux.
Term
 What image characteristics are present for acute thrombus?
Definition
 1. Dark intraluminal echoes2. Homogeneous echoes3. Distension of vein4. Poor wall attachment ("tail")
Term
 What image characteristics are present for chronic thrombus?
Definition
 1. Bright intraluminal echoes2. Heterogeneous echoes3. Possible retracted, small lumen4. Well attached to wall5. May see recanalization collaterals6. Vein may be invisible
Term
 How is Doppler ultrasoundused to diagnose venous valvular insuffciency?
Definition
 flow direction, proximal compression, distal release.
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