CH 18 - Hemodynamics Flashcards
the study of blood moving through the circulatory system
hemodynamics
flow / volume flow rate
indicates the volume of blood moving during a particular time
units - L/min
velocity
speed of a fluid moving from one location to another
units - cm/s
three basic forms of blood flow
pulsatile
phasic
steady
type of flow that occurs when blood moves with a variable velocity
pulsatile flow
blood has a variable velocity because of
cardiac contraction
pulsatile flow commonly appears in the ___ circulation
arterial
this type of flow also occurs when blood moves with a variable velocity, but because of respirations
phasic flow
phasic flow often appears in ___ circulation
venous
occurs when a fluid moves at a constant speed or velocity
steady flow
steady flow is present in the venous circulation when ___
individuals stop breathing for a brief moment
when the flow streamlines are aligned and parallel
laminar flow
laminar flow is characterized by layers of blood that travel at …
individual speeds
laminar flow patterns are normal or abnormal
normal
laminar flow has 2 terms
plug flow
parabolic flow
occurs when all of the layers of blood cells travel at the same velocity
plug flow
parabolic flow
bullet shaped profile
velocity is highest in the center of the lumen and gradually decreases at the walls of the vessel
Reynolds number
predicts whether flow is laminar or turbulent
laminar is less than 1500
flow that is characterized by chaotic flow patterns in many different directions and many speeds
turbulent flow
turbulence is often associated with a ___
pathology
sound associated with a turbulence
murmur
bruit
vibration associated with turbulence
thrill
a palpable murmur that you can feel with your fingertips
thrill
Reynolds number of turbulent flow
greater than 2000
why does blood move from one location to another
energy gradient - moves from high to low energy
what event provides energy to the circulating blood
systole
forms of energy in blood
kinetic
pressure
gravity
kinetic energy is associated with a moving object
has 2 factors
an objects mass (high mass, high kinetic energy)
the speed at which it moves (high speed, high kinetic energy)
pressure energy is a form of ___ or ___ energy
stored or potential energy
a form of stored or potential energy associated with any elevated object
gravitational energy
energy is lost in 3 ways in curculation
viscous loss
frictional loss
inertial loss
the thickness of a fluid
viscosity
viscosity units
Poise
the percentage of blood made up of red blood cells
hematocrit
how do we determine viscous energy loss in blood
hematocrit
normal hematocrit level
45%
occurs when flow energy is converted to heat as one object rubs against another
frictional energy loss
energy loss when speed of a fluid changes regardless of whether the fluid speeds up or slows down
inertial energy loss
the tendency of a fluid to resist changes in its velocity
inertia
inertial energy loss occurs during 3 events
pulsatile flow
phasic flow
stenosis
velocity increases as the vessel widens/narrows
narrows
narrowing in the lumen of a vessel
stenosis
a type of turbulence downstream from the stenosis
post-stenotic turbulence
describes the relationship between velocity and pressure in a moving fluid
Bernoulli’s principle (states that the sum of kinetic energy and pressure energy remains constant)
pressure-flow relationship
relationship between flow, resistance, and pressure gradient
pressure gradient increases when
flow increases or when
resistance increases
flow increases when
pressure gradient increases or
resistance decreases
Ohm’s Law
voltage = current x resistance
fluids
pressure
flow
resistance
electricity
voltage
current
resistance
electrical resistance units
ohms
resistance vessels in the circulatory systems are called
arterioles
what is the typical resistance of veins
low resistance vessels
how do veins adapt to increased inflow during periods of exercise?
the CSA of the vessel changes to oval and then round to accommodate a large volume increase
pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level
hydrostatic pressure
units - mmHg
clinical significance of hydrostatic pressure
when taking a patients blood pressure
supine
laying flat on back
during supine position, the hydrostatic pressure is
zero everywhere
