3.2.2. Hemodynamics Flashcards

1
Q

How does pressure relate to flow and resistance?

A

Delta P = Q x R

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2
Q

How does pulmonary resistance compare to that of peripheral resistance?

A

Pulmonary resistance is a lot lower than peripheral resistance.

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3
Q

What is 1 Peripheral Resistance Unit (PRU)

A

mmHg/(ml/sec)

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4
Q

How does flow relate to the radius of the vessel?

A

Q̇ α r4; the radius makes a huge difference in regard to flow

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5
Q

How does flow relate to vessel length?

A

Q̇ α 1/L

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6
Q

What is Poiseuille’s Law

A

Q̇ = kr4ΔP/L

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7
Q

What are 4 assumptions of Poiseuille’s Law?

A
  1. Flow is laminar
  2. Flow is through smooth cylindrical rigid tubes
  3. Velocity does not change
  4. Viscosity of the fluid is constant
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8
Q

In a vessel, where is the velocity the fastest?

A

The center.

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9
Q

How would you determine turbulent flow?

A

Depends on: radius of tube, density and viscosity of fluid
The mean velocity are combined into a dimensionless Reynolds Number (Re)
Allows you to estimate conditions producing turbulent flow
Re = 2r⊽ρ/η
⊽ = mean velocity
η = viscosity
If Re > 2000, turbulence is probable

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10
Q

Why is turbulent flow bad for the heart?

A

Wastes energy and makes the heart work harder for the same flow.

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11
Q

What qualities of a vessel contradict the assumption that blood flows through smooth cylindrical rigid tubes?

A
  1. Arterial plaques disrupt smooth arterial walls
  2. Diameter changes between diastole and systole
  3. Vessel diameter changes with pressure
  4. Branching
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12
Q

What is compliance? Formula?

A

A property of blood vessel undergoing a change in volume when subjected to an applied pressure.

C = ΔV/ΔP

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13
Q

How does compliance compare among arteries and veins?

A

The compliance of a systemic vein is ~24 times that of its corresponding artery

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14
Q

How does calcification affect vessel compliance?

A

Calcification increases wall stiffness and decreases vessel compliance.

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15
Q

How does the sympathetic activity affect compliance?

A

Stimulation causes decreased compliance. Inhibition causes increased compliance.

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16
Q

How does compliance change with age?

A

With age, compliance begins to decrease in the normal range of blood pressures
The heart is unable to eject its stroke volume as rapidly into the rigid vascular system.

17
Q

How does compliance relate to elastance?

A

Elastance = 1/Compliance

18
Q

When are Poiseuille’s assumptions better?

A

As you move further from the heart.

19
Q

What is a Newtonian fluid?

A

A fluid with a viscosity that is independent of the forces on it and the velocity of flow. Blood is a Newtonian fluid.

20
Q

At constant P, L and r, how does viscosity affect flow?

A

Increases in viscosity decrease flow

21
Q

The kidneys and GI tract are examples of resistances in…

A

Series

22
Q

The cardiovascular system is an example of resistances in …

A

Parallel

23
Q

Adding a resistor to resistance in series increases or decreases the total resistance?

A

Increases.

24
Q

Adding a resistor to resistance in parallel increases or decreases the total resistance?

A

Decreases