Physiology And Hemodynamics Flashcards
How much blood does the heart pump into the aorta when it makes a blood pressure pulse
70 milliliters
How does the aortic valve know to open in order to pump blood
When the left ventricle pressure exceeds the pressure in the aorta
______ heart rate delivers an ______ blood pressure.
Increase or decrease
INCREASED heart rate delivers an INCREASED blood pressure
Put the following in order from blood circulation out and back into the heart
*aorta *arterioles * venules. *Vena Cava. *left ventricle. *large arteries. *capillaries. *large veins. *right atrium
Left ventricle -> aorta -> large arteries -> arterioles -> Capillaries -> Venules -> large veins -> Vena cava -> right atrium
How does the heart help maintain a high pressure gradient between arteries and veins
The pumping action of the heart results in a high volume of blood into arteries
What determines the AMOUNT of blood entering the arterial system
Cardiac output
What determines the amount of blood leaving the arterial system
Arterial pressure and total peripheral resistance
Pressure is greatest at the ____, and decreases as it moves.
Greatest at the heart.
*the pressure difference helps maintain blood flow
Movement of any fluid medium between two points requires two things…. What are they
A pathway for fluid to flow Pressure difference (high pressure to low pressure)
The amount of flow depends on…
2
Energy difference (including losses resulting from fluid movement) Resistance that tends to oppose movement
What kind of resistance causes high flow rate
Low resistance
What kind of resistance causes lower flow rate
Higher resistance
The total energy contained in moving fluid is the sum of? (3)
Pressure
Kinetic energy
Gravitational energy
Potential/stored energy is which kind
Pressure energy
- released when walls recoil
- expressed in mmHg
Velocity is which form of energy
Kinetic energy
- small part of circulation
- expressed in fluid density and velocity (cm/s)
This type of energy is the weight of the column of blood extending from the heart to the level where pressure is measured
Gravitational energy (hydrostatic pressure…HP)
If there is a 0mmHg (HP) against arteries and veins at the ankle the patient is in what position
Supine (if patient is average size)
If an average sized supine patient decides to stand, what happens to the HP
Adds about 100mmHg to ankle vessels
Ankle pressure = circulation pressure plus 100mmHg
The tendency of fluid to resist changes in its velocity
Inertia
body at rest tends to stay at rest
As blood moves farther out to the periphery, energy dissipated largely in the form of _______
Heat
in the equation for resistance, R(resistance) is directly proportional to which two factors
Viscosity and length
*variables in the numerator of the equation
R= 8nL/(pie)r^4
In the equation for resistance, R(resistance) is inversely related to which variable?
Radius
*variable in denominator
R= 8nL/(pie)r^4
Of the three variables in the resistance equation, which one effects resistance the MOST
Viscosity, length, or radius
Radius
*a change in the radius means there was a change in the vessel diameter
The internal friction of a fluid is measured by?
Viscosity
What effect does elevated hematocrit have on the blood viscosity?
Will increase the blood viscosity bc it effects the THICKNESS of the fluid
What effect will anemia have on blood viscosity?
Decreases blood viscosity
____ viscosity = _____ velocity
Increased viscosity(friction) = DECREASED velocity While.... Decreased viscosity = INCREASED velocity
what term described flow that is evenly distributed during systole
Laminar
What kind of flow is considered “stable flow”
Laminar
______ flow is normally seen at vessel origin and/or initial cardiac upstroke
Plug flow
______ flow is usually seen downstream once the laminar flow is fully developed
Parabolic flow
Inertial energy loss occurs when this happens
2
Directional change and/or velocity change
What type of energy loss occurs at the end of a stenosis?
Viscous energy loss
Internal energy loss
Inertial energy loss
Poiseuilles equation helps define how much fluid volume moves through the vessel with these three variables
Pressure(P), volume flow(Q), resistance(R)
Q = P/R
Radius of a vessel is ______ proportional to volume flow
Directly
The law of conservation of mass explains the relationship between these two things
Velocity and area (inversely related)
Q = A x V
Benoullis law uses the relationship between what two variables
Pressure and velocity (inversely related)
Total energy contained in moving fluid is the sum of what?
the sum of pressure, kinetic and gravitational energy
What’s another name for pressure gradients
Flow separation
What can cause flow separation (pressure gradient) to occur? (3)
Regions with…
Reverse flow, stagnant flow, or little movement
EXAMPLES: valve cusp site, anastomosis of bypass graft
Reynolds Number(Re) helps to predict when fluid becomes unstable/disturbed by using these two variables
Pressure and flow relationship
With Reynolds Number (Re), laminar flow is considered disturbed when it is GREATER than this number
Greater than 2000
*unitless number
STEADY flow originates from a ____ _____ ____
Steady driving PRESSURE
This flow changes both driving pressure conditions as well as the response of the system
(Steady VS pulsatile)
Pulsatile flow
Describe what happens during systole
Aortic valve opens causing foward flow throughout the periphery (fluid acceleration)(initial release)
Describe what happens during late systole/early diastole
Temporary flow reversal due to a phase shift of negative pressure gradient and peripheral resistance
** think of the “biphasic” portion of a waveform
The dicrotic notch is related to the closing of ____ and the influence of _____ ______
Closing of aortic valve and influence of peripheral resistance
- when aortic valve closes diastole begins *
Describe late diastole
Flow is foward again
T/F
Diastole reflects where the blood is going to
TRUE
The ICA, vertebral, renal, celiac, splenic, and hepatic arteries are all examples of what resistance
LOW resistance
- organs you can’t live without *
The ECA, subclavian, aorta, iliac, fasting SMA, and arteries in extremities are all what type of resistance
High resistance
The reversal component in a high resistance waveform may disappear distal to ______ b/c of a decreased peripheral resistance
Stenosis
*this is secondary to ischemia
What is the appearance of a waveform that is distal to a significant stenosis
Can show…
low resistance
More rounded
Weaker strength
What kind of flow should we expect proximal to a significant stenosis
May become…
monophasic
Higher resistance
VasoCONSTRICTION causes medium/small arteries to have a ______ in pulsitility, and a ______ in minute arteries
Medium/small = increase Minute = decrease
VasoDILATATION causes medium/small arteries to have a ______ in pulsitility, and a ______ in minute arteries
Medium/small = decrease (lower resistance) Minute = increase
At rest, can blood flow seem normal even if there is a stenosis or complete occlusion of a main artery, why?
Yes, because of collateral networks
With arterial obstruction, the collateral channels may have an altered flow. What are the changes that occur in the collateral channel flow
Elevated velocity
Increased flow volume
Pulsatility changes
What are some causes of exercise
Peripheral vasodilation which lowers distal peripheral resistance, enhancing blood flow
Exercise helps regulate this due to the vasoconstriction and vasodilatation of the vessels in the skeletal muscles
Regulates body temperature bc of the sympathetic nervous system response
_____ is a key vasodilator of the resistance vessels in the skeletal system
Exercise
The ability of most vascular beds to maintain constant level of blood flow over a wide range of perfusion pressures is?
autoregulation
In resistant vessels, constriction causes BP to ___, and dilation causes BP to _____
Constriction = rise Dilatation = fall
A vigorous exercise causes vasodilatation, making the waveform look…
Low resistant with monophasic flow
Vasoconstriction and pulsatile waveform is seen with a warm or a cold extremity?
Cold
- warm extremity means vasodilatation and a continuous waveform
T/F
distal effects of obstructive disease may only be detectable following stress (exercise)
True
A hemodynamically significant stenosis causes a notable reduction in what two things
Volume flow and pressure
A cross sectional area reduction of 75% = a diameter reduction of what percent
50%
Effects of flow abnormality produced by a stenosis depends on factors such as…
Length/diameter/shape of narrowing
Multiple obstructions in the Same vessel
Obstructions in different vessels that are parallel
Pressure gradient
A dampened waveform is usually _____ to a stenosis
Proximal
Entrance into a stenosis produces an increased Doppler shift frequencies (DSF), which makes the waveform look like what
Spectral broadening ( wide range of velocities) Elevated velocities
Flow disturbance occurs with what kind of velocities
High velocities and eddy currents
Post-stenosis causes what kind of flow
Turbulence
(Flow reversal, flow separation, vortices/eddy currents
