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PHYS 216 > Hemodynamics > Flashcards

Hemodynamics Flashcards

1
Q

What is hemodynamics? What else does it refer to?

A

Study of blood flow in the circulatory system and refers to both power and blood

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2
Q

The circulatory is a closed circuit system that comprised of what? 4

A
  1. Heart
  2. Arteries,
  3. Capillaries
  4. Veins
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3
Q

Contracting muscles in the circulatory do what?

A

Act as the pump to get the blood back to the heart, sometimes called the venous heart

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4
Q

In the study of blood flow it is helpful to understand what? 3 (make up)

A
  1. Plasma consists (water and protein) of 55%
  2. Erythrocytes consists (RBC) of 45%
  3. Leukocytes and platelets <1%
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5
Q

What is hematocrit?

A

Perectage of blood that is red blood cell. Defined as the mass per unit volume or the resistance of an object to accelerate.

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6
Q

How much of the blood volume is referred to as hematocrits?

A

45%

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7
Q

In terms of hematocrits what is viscosity? What does this mean for velocity?

A
  1. Resistance to flow.
  2. The more viscous the blood the slower the velocity
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8
Q

The greatest amount of blood is where?

A

In the veins, it accounts for about 65%

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9
Q

Capillaries have an area of what? Compared to other vessels?

A

600-100X

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10
Q

What is the volume and velocity in the capillaries?

A

Relatively low

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11
Q

What do we need for any fluid to flow?

A

A pressure difference

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12
Q

How can a pressure difference be made created in the body?

A

Heart or gravity

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13
Q

For hemodynamics, an increase in pressure results in what?

A

Increased flow rate

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14
Q

Blood flowing in a vessel is synonymous with what?

A

Current flowing through a wire

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15
Q

What is the formula for ohm’s law?

A

Current = voltage/ resistance

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16
Q

In the body, the voltage is what?

A

The pressure gradient

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17
Q

What is the current in terms of hemodynamics?

A

Volume flow rate

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18
Q

What is pressure gradient?

A

The pressure difference divided by the distance between two pressure locations

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19
Q

What is the pressure gradient formula?

A

P gradient = (p1-p2)/L

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20
Q

What is volume flow rate (Q)?

A

The volume of blood passing a point per unit time

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21
Q

The total adult blood flow rate is what?

A

~ 5000 ml/min and is called the cardiac output

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22
Q

What is poiseuilles law for resistance? (Formula)

A

R = (8 x length x viscosity/ pie x radius^4)

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23
Q

What is poiseuilles law work on

A

Straight tubes only

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24
Q

When blood flows through vessels it can have different flow patterns depending on what? 4

A
  1. Diameter
  2. Tortuously
  3. Bifurcations
  4. Anastomoses
25
Q

What are the different types of flow patterns 5

A
  1. Plug
  2. Laminar (parabolic)
  3. Jet
  4. Disturbed
  5. Turbulent
26
Q

What is plug flow?

A

Seen at the opening of large vessels like the aorta and has almost all RBCs travelling at the same velocity

27
Q

What is laminar parabolic flow?

A

The RBC’s move in concentric layers with the ones in the Center moving faster than the ones near the wall.

28
Q

What is the most common of flow pattern in the body

A

Laminar parabolic flow

29
Q

What is Jet Flow?

A

The velocities within narrow openings are much faster then the rest

30
Q

Where do we see Jet flow?

A

When there is a significant reduction in the diameter of a vessel

31
Q

What is disturbed flow?

A

Occur naturally in the presences of vessels tapering, curvatures, bifurcations. Similar to laminar but not straight and has many different variations

32
Q

Where is an example of disturbed flow location?

A

Carotid bulbs

33
Q

What is turbulent flow?

A

Flow velocities are greatly varied as are flow directions and can be described as chaotic.

34
Q

Where do we usually see turbulent flow?

A

Past a stenosis, and is unusual in the body except in and near the heart

35
Q

What is Reynolds’s number (RN)?

A

Can predict the onset of turbulence in a vessel and is calculated from the following formula. 2000.

36
Q

What happens if RN is above 2000

A

Turbulence results

37
Q

What is the continuity rule?

A

In the presence of a stenosis the volume of flow must remain constant proximal to, at and distal to the stenosis

38
Q

How do we achieve the continuity rule?

A

The velocity of blood increases in a stenosis to keep the volume flow constant

39
Q

If the diameter of the stenosis is 1/2 of the normal vessel then what happens?

A

Velocity is doubled through stenosis to maintain the volume flow

40
Q

Bernoulli’s principles establishing a relationship between what?

A

Kinetic energy, gravitational potential energy and pressure in a frictionless fluid system

41
Q

How does Bernoulli’s system affect flow rate?

A

The volume rate is maintained and the energy within a fluid system is kept in balance as well

42
Q

Total fluid energy (E) is comprised of what?

A

Both potential energy and kinetic energy

43
Q

Potential energy is what in terms of Bernoulli’s principles?

A

The intramuscular pressure plus the gravitational potential energy

44
Q

In terms of Bernoulli’s principle pressure is produced by what? 3

A
  1. The contraction of the heart
  2. The hydrostatic pressure
  3. The static filling pressure
45
Q

At the stenosis there is what? And why is it necessary?

A

There is a pressure drop which is necessary for the fluid to accelerate through the stenosis and decelerate past the stenosis

46
Q

Pressure or potential energy is converted to what?

A

Kinetic energy (flow) on entry and back to pressure energy on exit

47
Q

The drop in pressure, in a stenosis, can be what?

A

Calculated using velocity of blood flow in the Jet with its simplified formula

48
Q

What is the formula for bernoullis principle

A

P = 4(V2)^2

49
Q

The velocity before the stenosis is small compared to what?

A

Jet and can be ignored

50
Q

Where do we use bernoullis Principle formula?

A

Echo for stenoitic heart valve

51
Q

What is tarsus parvus?

A

After a stenosis there is a drop in the acceleration time and peak systolic velocity of arterial flow

52
Q

What is the Windkessel Effect?

A

The windkessel effect is the continued forward flow in the aorta during diastole as a result of the elasticity of the vessel walls contracting back to their original diameter

53
Q

During the Windkessel effect, the flow can’t reverse back to the heart because of what?

A

The aortic valve has closed

54
Q

The pressure wave along the walls of the vessel travels what?

A

Faster then the blood travelling within

55
Q

When the wave reaches the end of the arterial system what happens?

A

There is a reflected wave that causes the vessel wall to expand and contract against the flow of blood

56
Q

If there is a increased pressure down stream and the heart is in diastole what happens?

A

Blood is reversed back towards the heart

57
Q

What part of the body is known as the venous heart?

A

Calf muscles

58
Q

The pressure wave velocity and blood flow velocity are related how?

A

Inversely

PHYS 216 (8 decks)

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