Chapter 2- Physiology And Hemodynamics Flashcards Preview

Vascular Boards > Chapter 2- Physiology And Hemodynamics > Flashcards

Flashcards in Chapter 2- Physiology And Hemodynamics Deck (42):
1

Name the flow of blood starting from the heart

1) Left ventricle
2) Aorta
3) Large arteries
4) arterioles
5) capillaries
6) venules
7) Large veins
8) Vena cava
9) Right atrium

2

Energy: Movement of any fluid medium between two points requires two things:

1) pathway along which fluid can flow
2) pressure differential ( high pressure moves to lower pressure)

3

What does the amount of flow depend on?

1) energy difference
2) any resistance which tends to oppose such movement

4

Grey box:

Lower resistance = higher flow rate
Higher resistance = Lower flow rate

.

5

What is the major form of Energy for circulation of blood?

Pressure (potential/ stored energy)

6

What is kinetic energy?

Velocity

- small for circulating blood
- expressed in terms of fluid density and velocity measurements

7

What is Gravitational energy?

Hydrostatic pressure (HP)

Weight of the column of blood extending from the heart to level where pressure is measured

8

An energy gradient is needed to move blood from one point to another. The _________ the gradient; the _________ the flow.

Larger; greater

9

What is Inertia?

Related to tendency of a fluid to resist change in its velocity (example: body at rest stays in rest)

10

Resistance if directly proportional to what?

Viscosity (thickness of blood) and length

11

Resistance is inversely related to what?

Radius

12

What has the most dramatic effect on resistance of a blood vessel?

Vessel diameter

13

Elevated hematocrit does what to blood?

Increases blood viscosity ( thickness of blood)

Severe anemia: decreases blood viscosity

14

Grey box:

Increase in viscosity = decrease in velocity

Decrease in viscosity = increase in velocity

.

15

What is parabolic flow?

Higher frequency flow in center of vessel. Laminar flow considered stable flow

16

Where is plug flow seen?

Vessel origin as well as during initial cardiac upstroke

Blunted flow

17

What causes viscous energy loss?

Increased friction between molecules and layers which ultimately cause energy loss

18

Where do inertial losses occur?

Deviations from laminar flow, due to direction and/or velocity changes

Example: exit of a stenosis

19

What does the Poiseuille’s equation show relationships of?

Pressure, volume flow, resistance

20

What is volume flow directly related to?

Pressure

21

What is volume flow inversely related to?

Resistance

22

What is the relationship between area and velocity?

Inversely related

- increase area ; decrease velocity
- decrease area ; increase velocity (ex: stenosis)

23

What is the relationship between velocity energy and pressure energy?

Inversely related
- increase in velocity = decrease pressure

- decrease in velocity = increase in pressure

24

What is boundary layer separation?

They occur because of chAnge with or without intra-luminal disease; and because of curves

25

In presence of flow separation, what happens with the velocity and pressure?

Decrease in velocity; increase in pressure

26

What is the Reynolds number when Laminar flow becomes disturbed?

> 2000 (unitless number)

AKA Turbulent flow

27

Looking at a triphasic waveform, what does the dicrotic notch tell us?

Related to closure of the aortic valve and the influence of peripheral resistance

28

What are examples of arteries that have low resistive waveforms?

- ICA
- vertebral
- renal
- celiac
- splenic
- hepatic

** main arteries that feed organs**

29

What are some examples of low resistive arteries?

- ECA
- subclavian
- aorta
- iliac
- extremity arteries
- fasting SMA

30

What can happen to a normal high resistant signal as it approaches a significant stenosis or obstruction?

Become monophonic

31

What does the diastole in a waveform reflect in low and high resistance?

Low resistance: higher diastole, continuous blood flow
High resistance: little to no diastole

32

What is vasodilation?

Pulsatilla changes in medium/ small sized arteries of the limbs are decreased (lower resistant). When this occurs, pulsatility changes are increased in minute arteries

33

Note:

We inflow pressure falls due to stenosis; the usual response in periphery’s to maintain flow by vasodilation

.

34

What is vasoconstriction?

Pulsating changes in medium/small sized arteries of the limbs are increased. When this occurs, pulsatility changes are usually decreased in the minute arteries.

35

Know about collaterals?

1) location of the collaterals may help to determine tentative location of the stenosis/obstruction
2) arterial obstruction may alter flow in collateral channels nearby or further away from site of obstruction

Changes include: elevated velocity, increase volume flow, pulsatility changes

36

Know about effects of exercising?

1) causes peripheral vasodilation which lowers distal peripheral resistance, enhancing blood flow
2)Vasoconstriction and vasodilation of blood vessels within skeletal muscles are influenced by sympathetic nervous system for blood temperature
3)Exercise is a key vasodilator of resistance vessels within skeletal muscle

37

What is auto regulation?

Ability of most vascular beds to maintain constant level of blood flow over a wide range of perfusion pressures

38

When Blood pressure rises, what happens to the resistance vessels?

Constrict

39

When blood pressure falls, what happens to resistance vessels?

Dilatation

40

Box:

Flow to a cool extremity (vasoconstriction) = pulsatile signals

Flow to a warm extremity (vasodilatation) = continuous, signals

.

41

Box:

Pulsatility changes don’t differentiate well between occlusion and severe stenosis

Waveforms may not be altered with good collateralization

.

42

What are effects of a stenosis?

1) notable reduction in volume flow and pressure
2) cross sectional area reduction of 75% = diameter reduction of 50%