Hemodynamics

Question 1

What is the study of blood moving through the circulatory system called?

Answer 1

Hemodynamics

Hemodynamics focuses on the movement and circulation of blood.

Question 2

What does flow indicate in hemodynamics?

Answer 2

Volume of blood moving during a particular time

Flow measurements answer the question ‘how much?’.

Question 3

What are the units for measuring flow?

Answer 3

/min (volume/time)

Flow is typically measured in volume per unit time.

Question 4

What are the three types of flow in hemodynamics?

Answer 4

• Pulsatile Flow
• Phasic Flow
• Steady Flow

These flow types describe how blood moves under different conditions.

Question 5

What does velocity measure in hemodynamics?

Answer 5

Speed or swiftness of a fluid moving from one location to another

Velocity answers the question ‘how fast?’.

Question 6

What are the units for measuring velocity?

Answer 6

cm/s (distance/time)

Velocity is measured in distance per time.

Question 7

What is pulsatile flow?

Answer 7

Blood moves with a variable velocity due to cardiac contraction

Commonly appears in arterial circulation.

Question 8

What is phasic flow?

Answer 8

Blood moves with a variable velocity due to respiration

Often appears in venous circulation.

Question 9

What is steady flow?

Answer 9

Fluid moves at a constant speed or velocity

Present in venous circulation when breathing stops briefly.

Question 10

What characterizes laminar flow?

Answer 10

Flow streamlines are aligned and parallel with layers of blood at individual speeds

It is known as silent flow.

Question 11

What are the two types of laminar flow?

Answer 11

• Plug flow
• Parabolic flow

These types describe specific profiles of laminar flow.

Question 12

What is the Reynolds number for laminar flow?

Answer 12

< 1,500

A Reynolds number below this value indicates laminar flow.

Question 13

What is plug flow?

Answer 13

All layers and blood cells travel at the same velocity

It results in a flat profile across the vessel.

Question 14

What is parabolic flow?

Answer 14

Velocity is highest in the middle and decreases at the vessel wall

It creates a bullet-shaped profile.

Question 15

What does the Reynolds number predict?

Answer 15

Whether flow is laminar or turbulent

It is a ratio between viscosity and inertia.

Question 16

What characterizes turbulent flow?

Answer 16

Chaotic flow patterns with multiple directions and speeds

Associated with cardiovascular pathology.

Question 17

What is the Reynolds number for turbulent flow?

Answer 17

> 2,000

A Reynolds number above this value indicates turbulent flow.

Question 18

What is a murmur in hemodynamics?

Answer 18

Sound associated with turbulent flow

It can indicate abnormal blood flow.

Question 19

What is a thrill in hemodynamics?

Answer 19

Tissue vibration associated with turbulent flow

Also known as a palpable murmur.

Question 20

What is the energy gradient in hemodynamics?

Answer 20

Blood moves from regions of high energy to low energy

This is driven by the contraction of the heart during systole.

Question 21

What determines kinetic energy in hemodynamics?

Answer 21

An object’s mass and speed

Kinetic energy is calculated using the formula KE = 1/2 MV².

Question 22

What is Pressure Potential Energy?

Answer 22

A form of stored energy; has the ability to perform work; a major form of energy for circulating blood and creates flow by overcoming resistance

Potential Energy (PE) = Mass x Gravity x Height

Question 23

Define Gravitational Energy.

Answer 23

A form of stored or potential energy associated with any elevated object

This energy is dependent on the height of the object above a reference point.

Question 24

What does Viscosity describe?

Answer 24

The thickness of a fluid

Units: Poise

Question 25

What is Viscous Energy Loss?

Answer 25

More energy is lost with movement of high viscosity fluids; viscous loss is associated with blood overcoming its internal stickiness; determined by Hematocrit ## Footnote Higher viscosity leads to greater energy loss.

Question 26

What does Hematocrit measure?

Answer 26

The percentage of blood made up of RBCs; normal value = 45% ## Footnote Hematocrit is crucial for understanding blood viscosity.

Question 27

What is Frictional Energy Loss?

Answer 27

Occurs when flow energy is converted to heat as one object rubs across another, i.e: blood rubbing/sliding against vessel walls

Question 28

What is Inertial Energy Loss?

Answer 28

Energy is lost when the speed of a fluid changes, regardless of whether the fluid speeds up or slows down; occurs during 3 events: * Pulsatile flow (arterial) * Phasic flow (venous) * Velocity changes at a stenosis

Question 29

Define Inertia in fluid dynamics.

Answer 29

Relates to the tendency of a fluid to resist changes in its velocity

Question 30

What is Stenosis?

Answer 30

A narrowing in the lumen of a vessel

Question 31

What occurs during Post-stenotic turbulence?

Answer 31

Turbulent flow downstream from the stenosis

Question 32

What does Bernoulli's Principle describe?

Answer 32

A modified law of conservation of energy; describes the relationship between velocity (kinetic energy) and pressure in a moving fluid (blood) ## Footnote When velocity is high, pressure is low and vice versa.

Question 33

Fill in the blank: The pressure gradient is equal to _______.

Answer 33

flow X resistance

Question 34

What happens to resistance to flow during stenosis?

Answer 34

Resistance to flow increases whenever there is a stenosis; in the circulatory system, the resistance vessels are called arterioles

Question 35

Describe Veins in the circulatory system.

Answer 35

Thin-walled, collapsible, low-resistance vessels; allows for large volume increases with very small pressure increases by changing shape from an hourglass, to oval, to round as inflow increases.

Question 36

What is Hydrostatic Pressure?

Answer 36

Pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level; units: mmHG

Question 37

True or False: Hydrostatic pressure is 0mmHG everywhere in a supine patient.

Answer 37

True

Question 38

What is the effect of Hydrostatic Pressure on measured pressures in an upright patient?

Answer 38

Hydrostatic pressure is negative at locations above the heart, creating erroneously low measured pressures; positive at locations below the heart, creating erroneously high measured pressures ## Footnote Measured pressure = circulatory pressure + hydrostatic pressure

Question 39

What happens to flow direction in a stenosis?

Answer 39

Change in flow direction ## Footnote Flow direction changes as the vessel narrows.

Question 40

What occurs to velocity as a vessel narrows due to stenosis?

Answer 40

Increased velocity ## Footnote Velocity increases as the vessel narrows.

Question 41

What type of flow is observed downstream from a stenosis?

Answer 41

Turbulence ## Footnote Turbulence is a common effect following a stenosis.

Question 42

What is the pressure gradient across a stenosis?

Answer 42

Pressure gradient exists ## Footnote A pressure gradient is present across the stenosis.

Question 43

What is lost due to stenosis?

Answer 43

Loss of pulsatility ## Footnote Pulsatility is diminished in the presence of a stenosis.

Question 44

According to Ohm's Law for fluid, what is measured at the ankle?

Answer 44

Pressure ## Footnote Pressure measurements can be taken at various points, including the ankle.

Question 45

What is the measurement site for pressure at the knee?

Answer 45

Knee ## Footnote Pressure is also measured at the knee level.

Question 46

What is the significance of the measurement at the waist?

Answer 46

Pressure ## Footnote Waist pressure measurements are relevant for understanding hemodynamics.

Question 47

What happens to thoracic pressure during inspiration?

Answer 47

Thoracic pressure decreases ## Footnote Inhalation leads to a decrease in thoracic pressure.

Question 48

What is the pressure measurement example mentioned?

Answer 48

140 mmHg ## Footnote 140 mmHg is referenced multiple times as a pressure measurement.

Question 49

What is the relationship between abdominal pressure and venous return?

Answer 49

Abdominal pressure increases, venous return decreases ## Footnote Increased abdominal pressure can lead to decreased venous return.

Question 50

What happens to the diaphragm during expiration?

Answer 50

Diaphragm moves upward into thorax ## Footnote The diaphragm's movement affects thoracic and abdominal pressures.

Question 51

Fill in the blank: During systole, flow reversal is seen during _______.

Answer 51

diastole ## Footnote Flow reversal occurs in diastole due to pressure changes.

Question 52

What is observed at area B in a stenosis?

Answer 52

Velocity is maximum, pressure is lowest ## Footnote Area B represents the site of maximum velocity and minimum pressure.

Question 53

What happens to venous flow in the legs during inspiration?

Answer 53

Venous flow in legs decreases ## Footnote Inspiration impacts venous return dynamics.

Question 54

What is the pressure at the top of the head in the context provided?

Answer 54

Pressure is variable ## Footnote The specific pressure values vary based on the reference point.

Question 55

What is the measured pressure at the far below heart level?

Answer 55

O mmHg ## Footnote Pressure measurements can be affected by hydrostatic factors.

Question 56

True or False: Pressure is higher in Area C than in Area B.

Answer 56

True ## Footnote Area C has higher pressure compared to Area B.