Arterial Physiology and Hemodynamics Flashcards
Cardiac contraction begins:
Pressure in the left ventricle rises rapidly.
Left ventricle pressure exceeds that in the aorta.
aortic valve opens, blood is ejected, BP rises
The heart pump:
Generates the pressure to move the blood.
Results in a pressure wave that travels rapidly throughout the system, demonstrating a gradual transformation as it travels distally.
Each beat pumps about how many milliliters of blood into the aorta causing a blood pressure pulse?
70
What governs the amount of blood that enters the arterial system?
Cardiac output
What determines the amount of blood that leaves the arterial system?
arterial pressure and total peripheral resistance
movement of any fluid medium between two points requires what two things?
A pathway along which the fluid can flow.
Difference in energy levels (pressure difference)
The amount of flow depends upon what?
Energy difference.
Any resistance which tends to oppose such movement.
Flow depends upon resistance and flow rate:
lower resistance=
higher resistance=
higher flow rate
lower flow rate
Total energy contained in moving fluid is the sum of what energies?
pressure, kinetic, and gravitational
What is the major form of energy for circulating blood?
pressure energy (mmHg)
What energy is small for circulating blood? Expressed in terms of fluid density and its velocity measurements.
kinetic energy
What is equivalent to the weight of the column of blood extending from the heart to level where pressure is measured?
gravitational energy or hydrostatic pressure
When supine there is 0 mmHg against the arterires and veins at the ankle. When standing the HP increases to what?
100 mmHg
An energy gradient is needed for what?
moving blood from one point to another. greater the gradient, the greater the flow.
R= 8nL/πr^4
R= resistance n= viscosity r= radius L= vessel length R is directly proportional to variables in numerator and indirectly to the variable in the denominator.
What has a more dramatic effect on resistance than viscosity and vessel length?
vessel diameter
factors affecting resistance to flow?
physical properties of the fluid and what its moving through
viscosity ans velocity
greater viscosity=
less viscosity=
less velocity
greater velocity
viscous energy loss is due to what?
increased friction between molecules and layers
Inertial losses occur with deviations from laminar flow due to what?
Changes in direction and/or velocity. occurs at the exit of a stenosis
Poiseuilles equation helps answer the question of how much fluid moves through vessel and defines the relationship between what?
Pressure, volume flow, and resistance
Q=P/R
area and velocity
greater area=
less area=
less velocity
greater velocity
pressure/velocity relationships
sum of pressure, kinetic, and gravitational energies. If one changes the others make up for the difference in order to maintain the original total fluid energy.
velocity and pressure
greater velocity=
less velocity=
less pressure
greater pressure
Systole:
Late systole/early diastole:
Late diastole:
Forward flow
Temporary flow reversal
Forward flow again
low resistance flow consists with what? continuous
ICA, vertebral, renal, celiac, splenic, hepatic
high resistance flow occurs in what? pulsatile
ECA, subclavian, aorta, iliac, extremity arteries, fasting SMA
Doppler flow distal to a significant stenosis is?
lower resistance, more rounded, and weaker in strength
Doppler flow prox to stenosis is what?
Higher resistance
A normally high resistant signal may become monophasic closer to stenosis.
Pulsatile changes in medium/small sized arteries of the limbs are increased. Pulsatility changes usually decreased in the minute arteries.
vasoconstriction
decreased pulsatile changes in medium/small arteries of the limbs. Pulsatility changes are increased in minute arteries.
vasodilatation
As the inflow pressure falls as a result of stenosis, the natural responsein periphery is to what?
Vasodialte to maintain flow
collateral effects
Increased flow volume Reversed flow direction Increased velocity Waveform pulsatility changes Location of collaterals helps provide tentative area of obstruction
Exercise should induce peripheral ______ which lowers distal peripheral ______, increasing blood flow.
vasodilatation, resistance
What is the best single vasodilator of resistance vessels within skeletal muscles?
exercise
What is the ability of most vascular beds to maintain constant level of blood flow over a wide range of perfusion pressures.
Autoregulation
BP rise:
BP fall:
Constriction of resistance vessels.
Dilatation of resistance vessels.
vasodilatation
vasoconstriction
what type of signals?
continuous, lower
pulsatile, higher
Entrance into stenosis increase in doppler shift frequencies resulting in what?
spectral broading and elevated velocities
post-stenotic turbulence
Flow quality is comprised of multiple changes in direction and spectral broadening as displayed by the spectral pattern.
Energy expended as heat.
