quick study guide 2

Reynold’s Number

• used to quantify the degree of turbulence

  • turbulence flow- when blood is flowing too fast

• Re >2000 = true turbulent flow

• ↑ in velocity, diameter, density —> ↑ Re

• ↑ in viscosity —> ↓ Re

Duty Factor between CW and PW

Hydrostatic Pressure (highest, lowest, at 0)

• the relationship between gravity, density, of the blood and a reference point

  • negative: ABOVE heart (top of head)

  • at 0: heart level

  • positive: BELOW heart level (ankles)

Bernoulli’s Principle

Hemodynamics: what it is

• the study of blood moving through the circulatory system

• can be lost in 3 ways:

  • Viscous Loss

    • ↑ viscosity —> ↑ energy loss —> ↓ blood flow

  • Frictional Loss

    • energy is converted to heat as blood slides across vessel walls

    • small vessel radius = ↑ friction and ↓ flow

    • friction causes laminar flow

  • Inertial Loss

    • energy is lost when there is a change in speed (ex: blockage)

Kinetic and Potential Energy

• Kinetic Energy- motion energy (a moving object)

• Potential Energy- pressure/stored energy (the ability to perform work)

• TOGETHER: equal 100%, when one goes ↑, the other goes ↓

Velocity: what causes it to increase/decrease Increase due to Stenosis

Relationship between Velocity and Radius

Lamina Flow and Friction

Doppler Shift and cos angles

cos angle for max:

cos angle for min:

Frasfarie: how it is analyzed

Images and how to fix

Correlation?

Doppler Shift Equation

fr (reflected frequency) - fo (transmit frequency)

Aliasing

Wall Filter- equivalent to rejecting low level signals

Spectral Broadening

Spectral Window

What affects Venous Flow

Viscosity and Unit

Pascal-seconds (Pa·s) or Poise (P)

Relationship between Flow and Resistance (smoothie and straw)

What affects blood flow resistance

• in blood flow, the resistance is in the arterioles

• Determined by:

  • length of vessel

    • longer vessel —> ↑ resistance

  • blood viscosity

    • ↑ viscosity —> ↑ resistance

  • radius of vessel

    • smaller radius —> ↑ resistance

    • has the most affect on resistance bc it is calculated to the 4th power (r^4)

What affects blood flow

• cardiac function

• compliance and capacitance

• cardiac muscle and vessel wall stiffness or tension

• vessel diameter change and branching patterns (vessel size)