Chapter 2 - Physiology and fluid dynamics

Question 1

Total energy made up of 3 components

Answer 1

1) Potential
2) Kinetic
3) Gravitational

Question 2

Source of potential energy (2)

Answer 2

1) heart pump

2) vessel distension (elastin)

Question 3

Kinetic energy depends on (2)

Answer 3

1) Density of blood

2) velocity of blood (squared)

Question 4

Types of laminar flow (2)

Answer 4

1) Parabolic flow (bullet shape)

2) Plug flow - all travel at same velocity

Question 5

Relationship of resistance to length and radius

Answer 5

R = 8nL / pir^4

n = viscosity
L = length
r = radius

Question 6

Define inertial loss (4)

Answer 6

1) change in direction
2) change in velocity
3) deviation from laminar flow
4) loss of energy

Question 7

Poiseuille’s Law

Answer 7

Q = P/R

Q = flow

Q = (P1 - P2) pi r^4 / 8nL

Question 8

Law of conservation of mass on velocity and volume and cross-section relationship

Answer 8

V = Q/A

V = velocity
Q = flow
A = cross sectional area

Question 9

Define eddy currents

Answer 9

small circular currents when streamline flow breaks

occurs with vortices

Question 10

Reynolds number (Re)

Answer 10

Re = Vp2r / n

V = velocity
p = density (constant)
n = viscosity (constant)
r = radius

Question 11

Reynolds number limit before turbulent

Answer 11

2000

Question 12

Bernoulli principle

Answer 12

velocity and pressure are inversely related

Question 13

Define flow separation and where it occurs

Answer 13

Defn: pressure gradients in a vessel

1) intraluminal disease
2) bifurcation
3) turn point

Question 14

Flow separation in systole and diastole

Answer 14

Systole: flow reversal
Diastole: stagnant, no movement/flow

Question 15

Define steady flow

Answer 15

1) steady driving pressure

2) energy losses described by Poiseuille’s equation

Question 16

Stages of pulsatile flow

Answer 16

1) Forward flow through periphery
2) Temporary flow reversal due to phase shifted negative pressure gradient and peripheral resistance
3) flow moves forward again
4) vessel recoil converting potential energy to kinetic energy

Question 17

Flow reversal decreases in:

Answer 17

1) vasodilation (exercise, heat)

2) stenosis

Question 18

Flow reversal increases in:

Answer 18

1) vasoconstriction

Question 19

Low resistance flow vascular beds (6)

Answer 19

1) ICA
2) vertebral
3) renal
4) celiac
5) splenic
6) hepatic

Question 20

High resistance flow vascular beds (6)

Answer 20

1) aorta
2) ECA
3) subclavian
4) iliac
5) extremity
6) fasting SMA

Question 21

Response to vasoconsctriction and vasodilation in medium, small and minute/capillaries arteries

Answer 21

Vasoconstriction:

• medium and small = increase flow
• minute/capillaries = decrease flow

Vasodilatation

• medium and small = decrease flow
• minute/capillaries = increase flow

Question 22

Effect of cardiac arrhythmia in assessing velocity

Answer 22

Difficult to accurately measure PSV

• take averages of few cycles (10)
• use velocity ratio instead

Question 23

Effect of aortic stenosis in assessing velocity

Answer 23

• delay in systolic upstroke

- decreased PSV (underestimate stenosis)

Question 24

Effect of aortic regurg/insufficiency in velocity waveform

Answer 24

1) pulsus bisferiens (double systolic peak)
2) diminished diastolic flow
3) reversed diastolic flow

Question 25

Other factors that increase peak systolic velocity

Answer 25

1) high cardiac output
2) young physically fit adults
3) anemia

Question 26

Low cardiac output on PSV waveform

Answer 26

1) lower velocity

2) rounded waveform

Question 27

Effect of intra-aortic balloon pump on PSV waveform

Answer 27

1) double peak

2) underestimate PSV

Question 28

Causes of increased systemic pulsatility in veins

Answer 28

1) upper extremilty and neck is normal
2) elevated right heart pressure (CVI, HF, tricuspid regurg/insufficiency, COPD, PH, CKD)
3) fluid overload (overhydration)

Question 29

Effect of obstruction on flow proximal and distal

Answer 29

Proximal = high resistance signal
Distal = low resistance monophasic pattern

Question 30

Hemodynamic significant stenosis requires this much diameter or lumen reduction

Answer 30

75% cross-sectional reduction

50% diameter reduction

Question 31

Effect of lesion in series

Answer 31

Worse than if single long lesion
Disturbed flow pattern at exit of lesion
- jet effect
- turbulence
- eddy formation

Question 32

Effect of lesions in parallel

Answer 32

overall resistance less than resistance in individual stenosis

Question 33

Non-narrowing factors that cause spectral broadening

Answer 33

1) Too large Doppler sample volume (sampling midstream and vessel wall together)
2) inappropriate doppler angle
3) doppler sample volume too close to wall