Lesson 20 (Part 2)

Question 1

Where is pulsatile flow observed?

Answer 1

In arteries

Question 2

What happens to the pressure and speed of blood as the heart beats?

Answer 2

They increase then decrease

Question 3

What do we observe in compliant vessels? (2)

Answer 3

1. Added forward flow

2. Reversal of flow

Question 4

Compliance

Answer 4

Expansion and contraction of non-rigid vessels during systole and diastole

Question 5

Widkessel effect

Answer 5

Added forward flow

Question 6

What happens to the vessel during systole?

Answer 6

It expands

Question 7

What happens to the vessel during diastole?

Answer 7

It contracts

- resulting in extended flow without driving pressure from heart

Question 8

What does pulsatile flow also have?

Answer 8

Flow reversal

Question 9

What happens to pulsatile flow in the aorta during diastole?

Answer 9

Blood doesn’t flow back, because aortic valve closes

Question 10

What happens to pulsatile flow in the distal circulation during diastole?

Answer 10

In some locations, when pressure decreases and vessel contracts
- there will be reversal of flow especially with no valves to prevent back flow

Question 11

What happens to speed at the stenosis?

Answer 11

It goes up

- eg) garden hose

Question 12

Why does speed go up at the stenosis?

Answer 12

To keep volumetric flow rate (Q) constant at all 3 regions

- before, at and after stenosis

Question 13

Continuity rule

Answer 13

Trying to keep Q constant all the time in all locations

- need to compensate to keep it as even as possible

Question 14

What is the formula for the continuity rule?

Answer 14

Q = V(average) x A
Q = volumetric flow rate (mL/s)
V = average velocity (cm/s)
A = cross sectional area (cm^2)

Question 15

What is volumetric flow rate for a short segment?

Answer 15

Constant

Question 16

If area decreases by 2x, what happens to the speed?

Answer 16

It increases by 2

Question 17

What happens to the volumetric flow rate if area decreases by 2?

Answer 17

It stays the same

- complies with the continuity rule

Question 18

What percentage does the vessels resistance begin to increase?

Answer 18

75%

Question 19

What happens at 75%? (2)

Answer 19

1. Q starts going down
   - eventually becoming 0 (occlusion)
2. V keeps going up
   - compensates for decrease in A
   - goes down near occlusion

Question 20

What can velocity determine?

Answer 20

The severity of the disease

Question 21

What is distance to stenosis?

Answer 21

Turbulence

Question 22

What is the sound produced by stenosis?

Answer 22

Brute

Question 23

What happens to the area if the radius goes down by 2x?

Answer 23

It goes down by 4

- pie r^2

Question 24

What happens to the velocity if the radius goes down by 2x?

Answer 24

It goes up by 4

Question 25

What do you use the formula Q=VxA?

Answer 25

In short segments

- usually stenosis

Question 26

When do you use the formulas Q=deltaP pie d^4/128Ln?

Answer 26

In long strait tubes

Question 27

What happens when speed goes up?

Answer 27

Pressure goes down

- indirectly proportional

Question 28

Bernoulli effect

Answer 28

Decrease in pressure in regions of high flow speed

- at stenosis

Question 29

What happens to pressure before stenosis?

Answer 29

Pressure goes up to push blood through stenosis

Question 30

What happens to pressure at stenosis?

Answer 30

Pressure goes down to maintain energy

- pressure energy = flow energy

Question 31

What happens to pressure after stenosis?

Answer 31

Pressure energy is the same as flow energy

Question 32

Where is pressure the slowest?

Answer 32

At the stenosis

Question 33

Where is flow the slowest?

Answer 33

Before and after stenosis

Question 34

Where is volumetric flow rate the lowest?

Answer 34

It will be the same throughout