Hemodynamics Flashcards
What is the purpose of the cardiovascular system?
Deliver blood and nutrients to tissues, removes wastes and cellular products from the cells
What part of the circulatory system is considered to be in series?
Pulmonary circulation
What part of the circulatory system is generally considered to be a parallel system?
Systemic circulation
What are the advantages of having the systemic circulatory system in parallel?
High pressure and highly oxygenated blood flow to all organ systems, allows for autonomic nervous system to regulate blood flow to different organs, and it exerts less strain on the heart since resistance is lower
What is cardiac output?
The amount of blood in L/min that is pumped out of the heart
What condition can develop as the result of diminished cardiac output?
Congestion
How can the resting/basal cardiac output be calculated?
8% of individual’s weight in kilograms
What happens to the cardiac output while exercising?
It increases
In a normal, stable CV system, what should the cardiac outputs of the left and ride sides of the heart be relative to one another?
Should be the same
What does it indicate if venous return does not equal the cardiac output?
Blood has been losr or gained somewhere along the path
What is the mean arterial blood pressure? What is the standard value?
The pressure exerted in the aorta to pump blood into systemic circulation; 93 mmHg
How can the mean arterial blood pressure be calculated?
MABP= (diastolic blood pressure)+1/3(pulse pressure)
How can pulse pressure be calculated?
Systolic blood pressure-diastolic pressure
How is the mean arterial blood pressure maintained?
The baroreceptor reflex
What determines the percentage of flow to each organ?
The function of the tissue
How can blood flow to a certain organ be calculated?
(CO)(% of flow to that organ)
How does blood flow to the brain change during exercise?
Stays relatively constant
What causes the loss of energy as blood flows through systemic circulation?
Friction
Why is the pressure lower in the vena cava than at the beginning of circulation?
Blood loses energy due to friction in the vessels
Where does the largest decrease in blood pressure occur?
Across the arterioles
How can the pressure gradient across the systemic circuit be calculated?
MABP-RAP
How can the pressure radient across the pulmonary circuit be calculated?
MPAP-LAP
What is the formula for flow rate?
Q/F=(High pressure-low pressure)/Resistance
What is required for any kind of flow?
A pressure gradient
What is the formula for systemic circulation cardiac output?
CO= (MABP-RAP)/SVR
What is the formula for pulmonary circulation cardiac output?
CO= MPAP-LAP/PVR
What is the formula for resistance?
change in pressure/ flow
Is the systemic or pulmonary vascular resistance greater?
Systemic circulation
What is Poiseuille’s Law?
Q= (Pressure gradient x pi x radius^4)/(8 x viscosity x length)
What is the major mechanism for changing blood flow?
Changing the radius of blood vessels (Arterioles)
What is the effect of decreasing the radius on resistance and blood pressure?
Increases resistance and blood pressure
What is the effect of increasing the radius on resistance and blood flow?
Decreases resistance and leads to increased blood flow
What can affect the viscosity of blood?
Hematocrit concentration, hydration, changes in temperature
How is resistance calculated in a series system?
Rtotal= R1+R2+R3
How is resistance calculated in a parallel system?
1/Rtotal= 1/R1+1/R2+1/R3
What is the formula for resistance using a derivation of Poiseuille’s law?
Resistance= 8 x viscosity x length/ pi x radius^4
True or false: All fluid in laminar flow is flowing at the same velocity
FALSE
Where is the velocity fastest in laminar flow?
In the middle of the vessel
What kind of flow results from blood moving at a high velocity through a narrow opening?
Turbulent flow
How can velocity be calculated?
V= Flow/area
What is the velocity of blood in the capillaries relative to the velocity in the aorta? What causes this?
Flow through the capillaries is slower then the aorta; there is a greater cross-sectional area of all capillaries than in the aorta
How is Reynold’s number calculated?
Re= (velocity x diameter x density)/ viscosity
There is a tendency for turbulence when Reynold’s number is above what value?
2000
What properties of blood affect flow?
Viscosity and elasticity
What is the relationship between viscosity and hemocrit and temperature?
Proportional to hemocrit and inversely proportional to temperature
True or false: Blood is a newtonian fluid
FALSE
What is the formula for compliance?
C= volume change/ pressure change
What is the inverse of compliance?
Elastance
What percentage of blood volume is contained in veins?
60%
What happens to compliance with age?
It decreases
What is elasticity?
The ability to return to the original shape or to resist deformation
What is occuring to the elastic walls of arteries during systole? During diastole?
Streching during systole and recoiling during diastole
What acts as a secondary pump during diastole?
Elasticity (recoil) of large arteries
What are the determinants of pulse pressure?
Stroke volume, speed of ventricular ejection, and atrial compliance
What is the formula for pressure?
P=F/A
What is the formula for hydrostatic pressure?
P=density x gravity x height
What is transmural pressure?
Pressure across te wall of a vessel
