103- Fundamental Hemodynamics Flashcards
Includes concepts from Hemodynamics simulation session
Suppose a rigid tube gets 10% longer while its radius increases by 10%.
Will the resistance increase or decrease? Why?
The resistance will decrease
The increase in radius will decrease resistance more than the increased length will increase resistance
What is diastolic pressure?
The lowest pressure attained during a cardiac cycle
Occurs right before the ventricles begin to contract
Are the pulmonary and systemic ciruculations in series or in parallel?
In series
What is the most important reason for maintaining sufficient cardiac output?
To maintain the diffusion gradient at the capillary beds
What is the equation for total resistance when resistors are in parallel?
The total resistance will be less than any one resistor in the system
(Think about students leaving a lecure hall when there are 3 doors open - students have multiple doors to go through, so the total resistance to students leaving is less than the resistance through any one door on its own)
What is the relationship between flow (Q), velocity (v), and cross-sectional area (A) of a blood vessel?
What is Pouiselle’s equation?
What does it help us understand?
Pouiselle’s law helps us understand factors that affect vascular resistance in a rigid tube
- Increased length and viscosity = increased resistance
- Increased radius = decreased resistance
- 4th power -> radius is the most powerful determinant of resistance
What is the pulse pressure in a patient with a blood pressure of 110/60?
50
Pulse pressure = SBP - DBP
110 - 60 = 50
Which blood vessls are considered “capacitance vessels” in the systemic cirulation?
Veins
They can stretch to accomodate more blood if necessary
What factors might cause tubulent blood flow?
- Physiologic
- Blood pressure measurement
- When we hear Korotkoff sounds, flow through the vessel is turbulent, because it is partially occluded by the blood pressure cuff
- Increased velocity
- Blood pressure measurement
- Pathologic
- Heart murmur
In a rigid tube, what happens to resistance as the length increases?
As the length increases, resistance increases
Which number predicts whether flow will be laminar or tubulent?
What is the equation?
Reynolds Number
(density X diameter X velocity)/(viscosity
Transition from laminar to turbulent flow at Reynolds number of ~2000
Which organ recieves circulation from both the systemic and pulmonary circuits?
The lungs
- Oxygenate blood recieved from the pulmonary circulation
- Need oxygen from systemic circulation blood in order to function
Which blood vessels are considered “conduit vessels” in the circulation?
Arteries, venules
Which blood vessels are considered “resistance vessels” in the systemic ciruclation?
Arterioles
They have a substantial smooth muscle layer that can contract to increase resistance
What is the equation for total resistance when resistors are in series?
What happens to flow (Q) if resistance (R) decreases, and the pressure gradient (P) stays the same?
Flow increases
What is compliance?
How is it calculated?
Compliance is the change in volume due to change in pressure
Basically, the stretchiness of a blood vessel
More compliant vessels will increase in volume in response to increased pressure (resulting in minimal pressure increase inside the blood vessel)
What is the equation that relates flow (Q), pressure (P), and resistance (R)?
Hint: The central dogma of cardiovascular medicine
How do you calculate the pressure in a hydrostatic column?
Why would we ever want to do this?
Pressure = density * gravitational constant * height of column
The jugular vein acts as a hydrostatic column; pressure in the jugular vein is a proxy for pressure in the right atrium
