16 Hemodynamics Flashcards
What is flow?
Movement of fluid from one location to another
What is steady flow?
Fluid moving at a constant speed or velocity
What is pulsatile and phasic flow?
Fluid moving at a variable velocity
What is the difference between pulsatile vs phasic flow?
Pulsatile - arterial, cardiac contraction, high rate, higher P
Phasic - venous, respiration, low rate, lower P
What is the difference between flow and velocity?
Flow - volume, how much?, vol/time (L/min)
Velocity - speed, how fast?, distance/time (m/s)
What is laminar flow?
Flow streamlines that are layered, aligned, and parallel
What are the different patterns for laminar flow?
Plug or parabolic
What is turbulent flow?
Chaotic flow in many directions and speeds
What is turbulent flow associated with?
CV pathology and increased velocities (stenoses)
What is flow energy converted to in turbulent flow?
Sound - murmurs, bruits
Vibration - thrill
What can turbulent be identified as?
Spectral broadening
What is a vortex?
A swirling pattern of rotational flow
What are eddy currents?
Turbulent flow
What is Reynold’s Number?
A unitless number indicating whether flow is laminar or turbulent
2000 = turbulent
What is the energy gradient?
When total fluid energy at one location differs from the total fluid energy at another location
What is kinetic energy?
Motion energy associated with object’s speed and mass
What is pressure energy?
Form of potential or stored energy that has the ability to perform work
What are 3 forms of energy loss?
Frictional loss
Viscous loss
Inertial loss
What is friction?
Conversion of other forms of energy into heat
What is viscosity?
Thickness of a fluid
Units = Poise
What is inertia?
Tendency of fluid to resist changes in its velocity
What does stenosis cause?
Change in flow direction Increased velocity, highest at max narrowing Turbulent flow at exit Pressure gradient Loss of pulsatility
What are the factors that determine resistance?
Radius of lumen
Length
Viscosity of fluid
What is Bernoulli’s Principle?
Law of Conservation of Energy At the most narrowed location - Velocity is highest Kinetic energy is highest Pressure energy is lowest
