Hemodynamics/Systemic Circulation Flashcards
What is the equation for calculating the Velocity of blood flow (generally)?
V = F/A
F = flow (ml/min) A = area (cm2)
What are the 2 factors that determine the rate of blood flow?
- pressure that pushes it
2. resistance to flow
What is the equation for Ohms law, which can calculate the flow of blood between 2 points along a vessel?
F = (change in Pressure)/Resistance
So using Ohms law (F = ΔP/R), if you increase pressure, will you increase or decrease flow rate?
Increase
So using Ohms law (F = ΔP/R), if you increase resistance, will you increase or decrease flow rate?
Decrease
If you increase the resistance in a vessel (like from atherosclerosis or a clot), what will happen to the organ DOWNstream from that vessel?
ISCHEMIA UP IN THIS BITCH
Let’s get weird. Give me the Poiseuilles law for blood flow.
F = (πΔPr^4)/(8nL)
ΔP= change in pressure r = radius of vessel n = viscosity of the blood L = length of tube
In Poiseuilles law, the radius of the vessel is to the 4th power. What does this mean as far as subtle changes to radius size on blood flow?
Subtle changes (inc or dec) causes a massive change in blood flow
Using Poiseulles law, if u increase the viscosity of the blood, do u increase or decrease blood flow rate?
Decrease!
remember n is on the bottom
also, making blood more viscous (thick) will be more sludgy.
So what factor can we actually test to determine the blood’s viscosity?
Hct
This feature of blood vessels allows them to accomodate the polsatile output of the heart and average them out, giving a smooth and continuous flow to the blood.
Distensibility
This is the point when blood vessels completely collapse because pressure falls below a critical level.
Critical closing pressure
This is the measurement of blood flow through a vessel for a given pressure.
Conductance (C = 1/R)
What is the R(total) for resistance of blood flow if vessels are arranged in series?
R(total) = R1 + R2 + R3 +R4…
So if you remove a series circuit from a vessel, will resistance go up or down?
Down!
Ex:
X = 2 + 2 + (2) –> X = 6
Remove 1: X = 2 + 2 –> X = 4
What is the R(total) for resistance of blood flow if vessels are arranged in parallel?
1/R(total) = 1/R1 + 1/R2 + 1/R3 + …..
So if you remove a parallel circuit from a vessel, will resistance go up or down?
Up!
Ex:
1/X = 1/2 + 1/2 + (1/2) –> X = 0.67
Remove 1: 1/X = 1/2 + 1/2 –> X = 1
This si the streamline blood flow of blood at a steady rate.
laminar flow
This is disorderly flow where blood flows cross-wise, forming whirls, causing increased resistance.
Turbulent flow
Turbulent flow increases directly in proportion to which 3 factors?
velocity of flow, diameter of the vessel, and density of the blood
Turbulent flow increases inversely proportional to which factor?
viscosity of blood
This device is where there is a recorder that is connected to a needle/catheter that’s directly inserted into an artery to measure blood pressure.
Transducer
What % deviation can a sphygmomanometer give when being compared to the measurements by a transducer?
10% deviation. it’s indirect.
This is the difference between systolic and diastolic pressures.
Pulse pressure
What is the pulse pressure if the systolic is 120mmHg and the diastolic is 80mmHg?
40
If there is a narrowed pulse pressure, what is that a sign of?
Increased resistance.
This is the avg of the arterial pressure over a period of time, determined by 60% of the diastolic and 40% of the systolic.
Mean arterial pressure (MAP)
What is the equation for MAP?
MAP = (1/3 systolic pressure) + (2/3 diastolic pressure)