Hemodynamics Ballam Flashcards
the rate at which blood is pumped from the ventricles is called the
cardiac output
cardiac output =
SV X HR
CO%: Cerebral
15%
CO%: Coronary
5%
CO%: Renal
25%
CO%: Gastrointestinal
25%
CO%: Skeletal muscle
25%
CO%: skin
5%
Three main mechanisms of distributing blood to the major organ systems: 1
CO is constant, but blood flow is redistributed among the organ systems by the selective alteration of arteriolar resistance
Three main mechanisms of distributing blood to the major organ systems: 2
CO increases or decreases, but %’s remain the same
Three main mechanisms of distributing blood to the major organ systems: 3
CO is altered AND %s are altered
Stressed Volume
the volume of blood in the arteries (under high pressure)
where is the site of highest resistance to blood flow
arterioles
arterioles have what kinds of receptors that do what
alpha 1 adrenergic receptors that cause vasoconstriction. vasoconstriction increases resistance
beta adrenergic receptors
at any given moment the greatest amount of blood is contained in the
veins
unstressed volume
% of blood in the veins (!00%)
veins have ____ receptors
adrenergic receptors, causing contraction and reducing their capacitance, therefore, reducing unstressed volume
velocity of blood flow =
v = Q/ A
Q = flow ml/s A = cross sectional area (cm squared)
A = pi(r^squared), r= radius
the units of velocity are
cm/s
as vessel diameter increases, velocity
decreases, because radius in the calculation for Area is squared, so it continually gets bigger
the relationship between pressure, resistance, and flow: formula
Flow (Q) / Delta Pressure/ R
Q = P/R
the magnitude of blood flow is directly proportional to
size of pressure difference
Q = P/R
Blood flow is _____ proportional to resistance
inversely proportional
Q = P/R
TPR
total peripheral resistance
can be measured by substitution Q (flow) with CO, and the pressure difference between vena cava and aorta
SVR
systemic vascular resistance (SVR) = TPR
Poiseuille equation tells us what
the relationship between resistance, blood vessel diameter and blood viscosity
the Poiseuille equation allows us to determine the resistance of the a blood vessel to blood flow.
Poiseuille equation: formula
R = (8 * viscosity of blood * length of blood vessel)/ (radius of blood vessel raised to fourth power * pi)
What big picture relationshops of the Poiseuille equation can we talk about without seeing numbers?
direct and indirect relations, and that with each increase in the radius of the blood vessel, the numerator is reduced by fourth power of the radius
when radius increases, resistance decreases
Total resistance of the system arranged in series is
equal to the sum of the individual resistances
R+R+R
Which factor in total vascular resistance is the most determinant?
arteriolar resistance
the greatest decrease in pressure occurs in the
arterioles, because they contribute the most to resistance
Parallel resistance
I/R (total) = 1/R + 1/R etc
as you add R’s, total R decreases
1500 foot level insights about parallel R and in series R
in series R: the total flow through all of the them will be equal, pressure decreases progressively
in parallel R: flow will be cumulative, each contributing a fraction to the overall flow, but the pressure in them all remains the same
Mean pressure of the Aorta
100 mmHg
Mean pressure of the Large arteries
100, 120 systolic, 80 diastolic
Mean pressure of the arterioles
50
Mean pressure of the capillaries
20
Mean pressure of the vena cava
4
Mean pressure of the Right Atrium
0-2
Mean pressure of the Pulmonary arteries
15: systolic 15, diastolic 8
Mean pressure of the pulmonary capillaries
10
Mean pressure of the pulmonary veins
8 mmHg
Mean pressure of the left atrium
2-5 mmHg
Which vessel has the most area? What is its volume?
capillaries have the most area but very little volume
Which vessel has the most volume? what is its area?
Veins have the most volume and the second most area after capillaries
Cardiac output = (Ballam’s formula)
(arterial pressure - venous pressure)/TPR (total peripheral resistance)
Laminar Flow
blood flow in the cardiovascular system is parabolic
blood towards the center is faster than blood near the vessel walls, as a result each successive layer of blood near the centers is a little bit faster
Velocity of blood at the vessel wall is __ and the blood at the center is
0
maximal
Turbulence
occurs when vessel wall has disturbances. fluid streams do not remain in a parabolic shape and begin to mix
often accompanied by murmurs
What is the energy profile of turbulence compared to laminar flow?
requires more energy to pump (in terms of pressure)
often
Reynolds number
dimensionless number that predicts whether blood flow will be laminar or turbulent
Reynolds number =
(density of blood)(diameter of blood vessel)(velocity of blood flow)/ viscosity of blood
2000
if reynold’s is above 2000, blood flow will be turb
if reynolds is below 2000, blood flow will be laminar
Increasing what 3 factors will increase Reynold’s number?
density of the blood
diameter of the blood vessel
velocity of the blood
Decrease what factor will increase Reynold’s number
viscosity of the blood
bruits
heart sounds made when reynold’s is turbulent
ateriosclerosis
lesions
Compliance of bloodvessels
how much the vessel can expand in response to a given chance in lumen hydrostatic pressure
compliance =
(change in volume)/(change in pressure)
compliance of arteries vs veins
vein > arteries
C = V/P
What kind of compensation does an old artery need in order to hold the same volume as a young artery?
it has to have more pressure
Diacrotic notch
is a slight dip in aortic pressure below systole when the aortic valve closes. closure produces momentary retrograde movement of blood back toward valve, causing pressure dip.
Pulse pressure
the pressure difference between systole and diastole
mean arterial pressure =
diastolic pressure + 1/3 Pulse Pressure
increasing smooth muscle causes
shift in compliance, moving blood from veins to arterial side and increasing pressure
compliance itself doesnt really change but shifts curve downward
lesions of the arteries will cause
decrease in compliance = pressures in the arteries will be increased
compliance is determined by the _____ pressure
pulse pressure , which is the difference is between diastole and systole
Equation for
Velocity
Resistance
Reynold’s number
Blood flow
compliance
v = Q/A
R = (L * viscosity * 8)/(pi r^4) so think R = 1/ r^4
Reynolds = (Density * Velocity * diameter of vessel)/viscosity of blood
Q = deltaP/R
Compliance = V/P
effect of aortic stenosis on arterial pressure
causes a decreases in aortic pressure
effect of arteriosclerosis on arterial pressure
increases pressure
how would an increase in resistance effect the pulse pressure?
it wouldnt change, but the mean pressure would increase
Swansgans catheter
put in the jugular vein, goes
vein —> right atria –> right ventricle —> pulmonary artery: balloon opens here
tells us pressure in left atrium, left ventricle but actually a little bit greater than left ventricle pressure
