Hemodynamics Flashcards
Hemodynamics is the study of what?
blood moving through the circulatory system.
What is flow?
aka: volume flow rate
indicates the volume of blood moving during a particular time.
Flow answers what question?
How much
Flow answers what question?
How much
what does velocity indicate?
the speed of moving fluid from one location to another.
Velocity answers what question?
how fast
What are the 3 basic forms of flow
- pulsatile
- phasic
- steady
what is pulsatile flow?
blood flow with a variable velocity.
As a result of cardiac contraction
What is phasic flow?
as a result of respiration
Steady flow is what?
fluid moving at a constant speed.
What are the 2 forms of laminar flow?
- Plug flow
- parabolic flow
What is plug flow
all layers of blood travel at the same velocity.
Often seen at the beginning of vessels.
what is parabolic flow?
velocity is highest in the center of the lumen.
What does the reynolds’s number predict?
whether flow is laminar t or turbulent.
what reynolds’s number predicts turbulent flow?
<2000
turbulent flow is often characterized by what?
chaotic flow patterns in many different directions and speed.
What is a sound associated with turbulence?
murmur or bruit
What is a vibration associated with turbulence?
A thrill
blood moving from regions of higher energy to lower is called what?
an energy gradient
What are the three forms of energy?
- Kinetic
- Pressure
- gravitational
kinetic energy is associated with what?
a moving object
Pressure energy is a form of what?
stored or potential energy
Potential energy has the ability to do what?
Perform work
gravitational energy is associated with what?
any elevated object
What are the 3 ways energy is lost through circulation?
- viscous loss
- frictional loss
- inertial loss
what is viscous energy loss?
has to do with the thickness of blood
In what 3 ways does inertia energy loss happen?
- pulsatile flow
- phasic flow
- velocity changes at a stenosis
What are 5 effects of a stenosis?
- change in flow direction
- increased velocity as vessel narrows
3 turbulence downstream from the stenosis - pressure gradient across the stenosis
- loss of pulsatility
Bernoulli describes the relationship between what?
between velocity and pressure in a moving fluid
What is the law of conservation of energy
energy is neither created nor destroyed.
States that pressure energy is lowest wherever the kinetic energy is the highest, at the narrowest part of the lumen.
What is the formula for pressure gradient?
Pressure gradient=flow x resistance
What is the relationship between pressure gradient and flow/resistance?
Directly.
When Pressure gradient increases, flow and resistance increases.
What is hydrostatic pressure?
pressure related to the weight of blood pressing on a vessel.
What is the hydrostatic pressure of a supine individual?
0
what is the formula for measured pressure?
Measured pressure= circulatory pressure + hydrostatic presure.
What is the arterial pressure measured in the toe of the upright patient?
240mmHG
Hydrostatic pressure= 100mmHG
Pressure generated by the heart is 140 mmHG
100+140=240mmHG
What is the arterial pressure measured at the standing patients upper arm?
140mmHG
Hydrostatic pressure = 0mmHG
Pressure generated by the heart = 140mmHG
0+140=140mmHG
What is the arterial pressure measured at the finger when the patient fully extends an arm toward the sky?
90mmHG
Hydrostatic pressure= -50mmHG
Pressure generated by the heart= 140mmHG
-50+140=90mmHG
Normally, what happens to venous flow in the legs during inspiration?
Venous flow in the legs decreases.
What is the primary reason blood moves from on location to another?
energy gradient
Which of the following causes the greatest amount of inertial energy loss?
pulsatile flow
flow through a stenosis
phasic flow
steady flow
parabolic flow
Flow through a stenosis
flow through a stenosis causes the greatest velocity changes and greatest inertial loss.
What happens to the diaphragm when an individual breathes in?
diaphragm descends into the abdomen
What happens to venous return to the heart when an individual inhales?
venous return to the heart increases.
What happens to venous flow in the legs during inhalation?
Venous flow in the legs decreases
What happens to the diaphragm when an individual breathes out?
It moves up into the chest cavity
What happens to venous return to the heart during exhalation?
Venous return to the heart decreases.
