Chapter 18: Hemodynamics

Question 1

Definition of flow

Answer 1

Amount of blood flowing through an area. Also known as volume flow rate

Question 2

What are the 3 types of flow

Answer 2

Pulsatile, phasic and steady

Question 3

What are the characteristics of pulsatile flow

Answer 3

Variable velocity, results from cardiac contraction, found in arterial circulation

Question 4

What are the characteristics of phasic flow

Answer 4

Variable velocity, caused by respiration, found in venous circulation

Question 5

What are the characteristics of steady flow

Answer 5

Constant speed, found NORMALLY in portal system. If found in arteries or veins then it is because of changes in respiration or disease

Question 6

Describe laminar flow

Answer 6

Consists of parallel streamlines, found in normal physiology

Question 7

What are the 2 types of laminar flow

Answer 7

Plug flow and parabolic flow

Question 8

Describe plug flow

Answer 8

Seen at the beginning of a vessel, happens when all of the layers travel at the same velocity

Question 9

Describe parabolic flow

Answer 9

When blood flow starts traveling in different velocities, and forms like a bullet shape

Question 10

Describe turbulent flow

Answer 10

Chaotic streamlines, seen following pathology, causes swirling patterns called eddy

Question 11

Palpable turbulent flow is called

Answer 11

Thrill

Question 12

Audible turbulent flow is called

Answer 12

Bruit

Question 13

What is the Reynolds number for laminar flow

Answer 13

<1500

Question 14

What is the reynolds number for turbulent flow

Answer 14

> 2000

Question 15

Blood moves from ____ energy areas to ____ energy areas

Answer 15

High, low

Question 16

What are the 3 forms of energy

Answer 16

Kinetic energy, pressure energy, and gravitational energy

Question 17

Describe kinetic energy

Answer 17

Any moving object, determined by object mass and speed

Question 18

Describe pressure energy

Answer 18

Stored or potential energy, has the ability to perform work, creates flow by overcoming resistance

Question 19

Describe gravitational energy

Answer 19

Stored or potential energy, has the ability to do work, associated with any elevated object (above earth)

Question 20

Energy gets lost in circulation in 3 ways:

Answer 20

Viscous loss, frictional loss, and inertial loss

Question 21

Describe viscous loss

Answer 21

Measured in units of Poise, it’s the thickness of blood, determined by hematocrit

Question 22

Describe frictional loss

Answer 22

Caused by blood sliding across vessel walls, creating heat and loosing energy

Question 23

Describe intertial energy loss

Answer 23

When energy is lost when the speed of blood changes (resisting velocity)

Question 24

What is stenosis

Answer 24

Narrowing of lumen of a vessel

Question 25

What are the 5 changes to blood flow that a stenosis causes

Answer 25

1.Change in flow direction 2.Increased velocity through narrowing 3. Turbulence after narrowing 4. Pressure decreases across the stenosis 5. Loss of pulsatility (from pulsatile to steady)

Question 26

Bernoullis principle describes the relationship between _______ and ________ in a moving fluid

Answer 26

Velocity and pressure

Question 27

If velocity increases, pressure ______

Answer 27

Decreases. And viceversa

Question 28

In a stenosis, velocity increases, so pressure _______

Answer 28

Decreases

Question 29

Electrical resistance is reported in units of ____

Answer 29

Ohms

Question 30

Hydrostatic pressure is reported in units of

Answer 30

mmHg

Question 31

Pt lying in supine position, hydrostatic pressure is ____ everywhere

Answer 31

Zero

Question 32

Hydrostatic pressure at heart level is ____

Answer 32

Zero

Question 33

Hydrostatic pressure below heart level is

Answer 33

Positive

Question 34

Hydrostatic pressure above heart level is

Answer 34

Negative

Question 35

During inspiration, the diaphragm goes ____

Answer 35

Down

Question 36

During inspiration, the pressure in the abdominal cavity ______

Answer 36

Increases. Reducing flow from lower body

Question 37

During inspiration, the pressure in the thorax_____

Answer 37

Decreases. Allowing blood flow from upper body

Question 38

During expiration the diaphragm goes___

Answer 38

Up

Question 39

During expiration, the pressure in the abdominal cavity____

Answer 39

Decreases. Allowing flow from lower body

Question 40

During expiration, the pressure in the thorax _____

Answer 40

Increases, reducing blood flow from upper body