CVT 100 #7 Physics PP Flow Behavior

Question 2

Laminar blood flow:

Answer 2

moving in concentric layersLaminar flow is orderly,undisturbed flow.

Question 3

Two configurations of laminar flow:

Answer 3

1. Parabolic profile 2. Plug or blunt profile

Question 4

Spectral Doppler from internal carotid artery:

Answer 4

Systolic upstroke has very narrow range of velocities (plug) Diastolic component has wider range of velocities (parabolic)

Question 5

Parabolic flow profile: Velocity highest in center…

Answer 5

Velocity highest in center,dropping off toward walls

Question 6

Parabolic flow profile: Peak velocity is twice…

Answer 6

Peak velocity is twice the mean velocity

Question 7

Parabolic flow profile: Velocity at walls is…

Answer 7

Velocity at walls is (theoretically) zero

Question 8

Plug flow profile: Velocities are the same…

Answer 8

Velocities are the same almost all the way across the lumen (Wall drag still slows down the outer layers)

Question 9

Parabolic flow profile:

Answer 9

All the time in steady flow Throughout cardiac cycle in small arteries (< 3 mm) During diastole in larger arteries

Question 10

Plug flow profile:

Answer 10

Systole in larger arteries (> 3 mm) Also, entrances to branches, entrance to stenosis

Question 11

Disorderly flow:Turbulence

Answer 11

Breakdown of laminar, orderly character of flow Many velocities, many directions Chaotic flow character

Question 12

Turbulence in the heartcauses

Answer 12

a murmur

Question 13

Turbulence in the vascular systemcauses

Answer 13

a bruit (broo-ee) (French word for “noise”)

Question 14

A cardiac murmur during systole is…

Answer 14

Systolic cardiac murmurcan be normal. (“functional murmur”)

Question 15

A cardiac murmur during diastole is…

Answer 15

Diastolic murmuris never normal.

Question 16

Factors that increase the likelihood of turbulence:

Answer 16

the Reynolds number Dimensionless number predicting likely onset of turbulence

Question 17

“Flow disturbance”suggests some degree of

Answer 17

interaction of the laminae (layers)in laminar flow

Question 18

Turbulence is the extremeof flow disturbance:

Answer 18

many velocities, many directions.

Question 19

Loss of laminar flow due to metal pin at top, creating “vortex streets”—… The degree of disturbance depends on several factors in the Reynolds equation, Coming soon.

Answer 19

the semi-orderly disturbance downstream.

Question 20

Basilar artery joins the… then bifurcates into… There is little mixing of the flow from right and left vertebrals within the basilar artery.

Answer 20

Basilar artery joins the two vertebral arteries, then bifurcates into right and left posterior cerebral arteries. There is little mixing of the flow from right and left vertebrals within the basilar artery.

Question 21

There is little mixing of the flow from____________ within the basilar artery.

Answer 21

right and left vertebrals

Question 22

The Reynolds equation: V= p= d= n=

Answer 22

Re = Vpd ——- n V = velocity p = density d = diameter n = viscosity

Question 23

If velocity,density, or diameteris increased,

Answer 23

the likelihood of turbulence is increased.

Question 24

Bigger diameter—>

Answer 24

—>more room for un-laminar flow to get started(walls help to stabilize flow)

Question 25

Higher density—>

Answer 25

—>more particles to bump together and disturb flow

Question 26

Higher velocity—>

Answer 26

—>more chance for particles to bump together, layers to interact,and disturb flow

Question 27

Flow in aorta can get somewhat turbulent in an

Answer 27

exercising person—bigger diameterand faster velocities(due to stronger LV contractions—remember?)

Question 28

Viscosity is internal friction created by

Answer 28

molecular attraction,creating a tendency to resist motion.

Question 29

If viscosity is increased,the likelihood of turbulenceis…

Answer 29

decreased. (Molasses vs. waterin the upper Kern River)

Question 30

What happens to Reynolds number if viscosity is cut in half?

Answer 30

Re = Vpd = (2) (2) (2) —> (2) (2) (2) ——- ————– ————- n (2) (1) Inversely proportional: Re is doubled. (More likelihood of turbulence)

Question 31

What happens to Reynolds number if velocity is doubled?

Answer 31

Re = Vpd = (2) (2) (2) —> (4) (2) (2) ——- ———— ————- n (2) (2) Directly proportional: Re is doubled. (More likelihood of turbulence)

Question 32

Stenosis:

Answer 32

Reduction of area causes increased velocity within stenosis(in arteries, usually the result of plaque)

Question 33

Proximal to stenosis:

Answer 33

Laminar flow, normal pressure

Question 34

Within stenosis:

Answer 34

Increased velocity, lower pressure against walls

Question 35

Distal to stenosis:

Answer 35

Turbulence and decreased velocity depending on severity of stenosis (along with decreased pressure and decreased flow distally if the stenosis is “critical”)

Question 36

Also: Waveforms distally will manifest ____ _____ ______ due to stenosis, depending on the severity.

Answer 36

loss of energy

Question 37

Note:Two separate phenomena The pressure drop WITHIN a stenosis is due to… The pressure drop DISTAL to a critical stenosis is due to…

Answer 37

Bernoulli effect (high velocity over the surface);it is local. the loss of energy created by the stenosis; it shows up everywhere beyond the stenosis

Question 38

Bernoulli effect, it’s time to meet Daniel Bernoulli (1700-1782)Discovered that …

Answer 38

Discovered that pressure in a flowing fluid is lowest where the speed is greatest. (Blow over top of paper) This keeps airplanes up in the air.

Question 39

Air has farther to travel over top of wing, so has to go faster. Faster flow over top—>

Answer 39

—> lower pressure Higher pressure pushes up

Question 40

The boomerang:

Answer 40

the Bernoulli effect makes it fly,and gyroscopic precession makes it go in a circle (return)

Question 41

The frightening Bernoulli equation

Answer 41

E = 1/2 d v2 + dgh + P — V The important thing: v and P are inversely proportional, since energy must remain the same.(dgh is gravitational potential energy)

Question 42

Real-life application:Modified Bernoulli equation

Answer 42

P1-P2 = 4 (V2) Finds pressure gradient across a cardiac valve in mmHgbased on velocity in m/sec

Question 43

If velocity = 200 cm/sec= 2 m/sec

Answer 43

∆P = 4 (22) = 4 ( 4 ) = 16 mmHg pressure gradient across the valve

Question 44

If velocity is 3 m/sec

Answer 44

∆P = 4 (32) = 36 mmHg gradientacross the valve (Again, stenosis causes loss of energy distally depending on severity of narrowing.)

Question 45

Velocity in an aortic valve is5.2 m/sec What is the pressure gradientacross the valve?

Answer 45

solve

Question 46

Another real-life implication: Greatly increased velocities within an arterial stenosis can help to disrupt the surface of the plaque and promote embolic activity.

Answer 46

(“Bernoulli effect sucking on the plaque.”)