DMS 219

• Flow is also called volume flow rate.
• Velocity indicates the speed or swiftness of a fluid moving from one location to another.
• Three basic forms of blood flow are:

  Pulsatile, phasic, and steady
• Pulsatile flow occurs when blood moves with variable velocity as a result of cardiac contraction.
• Pulsatile flow is most commonly seen in arterial circulation.
• Phasic flow occurs when blood moves with variable velocity due to respiration.
• Phasic flow is most often seen in venous circulation.
• Steady flow occurs when a fluid moves at a constant speed or velocity.
• Steady flow is present in the venous circulation when individuals stop breathing for a moment.
• What is laminar flow ?

  When flow is aligned and parallel
• What are the two types of laminar flow ?

  Plug flow and parabolic flow
• Plug flow occurs when all of the layers and blood cells travel at the same velocity.
• What is parabolic flow ?

  Bullet shaped profile; velocity is highest in the center and gradually decreases to its minimum at the vessel wall.
• What does the Reynolds number predict ?

  whether flow is laminar or turbulent
• What is the Reynolds number for laminar flow ?

  less than 1500
• What is turbulent flow ?

  Irregular and chaotic flow of a fluid.
• Small hurricane-like, swirling, rotational patterns that appear in turbulent flow are called what ?

  Eddy current or vortex
• Sound associated with turbulent flow is called what ?

  murmur or bruit
• Tissue vibration associated with turbulence is called a:

  thrill
• What is the Reynolds number for turbulent flow ?

  Greater than 2000
• What forms of energy are associated with blood ?

  Kinetic, pressure, and gravitational
• Heavy, fast moving objects will have high kinetic energy; light, slow moving objects will have low kinetic energy
• Kinetic energy is associated with a moving object.
• Pressure energy is a form of potential energy
• Gravitational energy is a form of potential energy.
• Gravitational energy is associated with any elevated object.
• Blood loses energy in three ways: viscous loss, frictional loss, and inertial loss.
• What is viscosity ?

  thickness of a fluid
• Viscous energy loss in blood is determined by hematocrit.
• Frictional losses occur when flow energy is converted to heat as one object rubs against another.
• In inertial loss, energy is lost when the speed of a fluid changes.
• Inertia relates to the tendency of a fluid to resist changes in its velocity.
• Inertial energy loss occurs during 3 events: pulsatile flow, phasic flow, and when velocity changes at a stenosis
• Velocity increases as the vessel narrows. Maximum velocity exists where the vessel is narrowest.
• Velocity decreases as blood flows out of the stenosis into a vessel segment of normal diameter.
• A stenosis is a narrowing in the lumen of a vessel.
• What effects does stenosis have on blood flow ?

  Change in flow direction, increased velocity within stenosis, turbulence after stenosis, pressure gradient across stenosis, and conversion of pulsatile flow to steady flow
• Bernoulli's Principle describes relationship between velocity and pressure in a moving fluid.
• Bernoulli's Principle is derived from the law of conservation of energy.
• When pressure increases, velocity will decrease.