Blood Pressure Flashcards
What is blood flow
pressure difference between 2 points of body over resistance (measured in mL/min)
what is blood pressure
force extered by blood against vessel walls
What does blood resistance depend on
Viscosity of blood (depends on hematocrit)
Length (fixed)
Radius
What is the formula for blood flow
Blood flow = pressure difference x radius of vessels
What causes reflective waves in the blood
Fast blood in bigger arteries is coming down to hit slower blood in smaller arteries, which causes the pressure to jump back and hit the walls
Why are reflective waves not a problem in healthy arteries? Why are they a problem in diseased/stiff ones?
In healthy arteries, The forward and the reflective waves are far enough apart that they don’t overlap too much.
In diseased arteries, The foreward and reflective waves are too fast, they sit on top of each other, which causes higher blood pressure reading. However,, the higher blood pressure may not be the pressure out of the heart, it may be the pressure back to the heart.
What is augmented blood pressure
the extra pressure in arteries caused by blood wave reflections, increasing the heart’s workload.
What is impedance change
Impedance is like a roadblock that makes it harder for blood to flow smoothly.
It’s different from resistance because it affects changing (pulsatile) flow, not just steady flow.
Blood vessels create impedance when they narrow, branch, or stiffen, which changes how pressure waves move through them.
It’s measured by looking at how pressure and flow waves interact in arteries.
What are three ways to take blood pressure
- Semi Manual w the stethoscope
- Cathetor inside the heart
- Fully manual with machine
What is PTT and what does it tell us?
Pulse Transit Time (PTT) is the time it takes for a pulse wave to travel between two arterial sites, usually from the heart (ECG) to a peripheral artery (like a fingertip or earlobe).
It is usually measured as the time delay between: The R-wave on an ECG and the arrival of the pulse wave at a peripheral site (shown on PPG)
PTT is inversely related to blood pressure—as blood pressure increases, the arteries become stiffer, making the pulse wave travel faster (shorter PTT). Conversely, lower blood pressure leads to longer PTT.
What is filtering
a manipulation of a signal in the frequency domain
What are the 4 types of filters
- Low pass
- High pass
- Band pass
- Band stop
What is a low pass filter
Allows low frequencies to pass and blocks high frequencies.
What is a high pass filter
Allows high frequencies to pass and blocks low frequencies.
What is a band pass filter
Allows a specific range of frequencies to pass and blocks frequencies outside this range.
Real-life analogy: A nightclub bouncer that only allows people within a certain age range (e.g., 18-35 years) inside.
What is band stop filter
What it does: Blocks a specific range of frequencies while allowing everything else to pass.
What is the difference between higher order and smaller order filters
Higher order (more taps) → Sharper cut-off, smaller transition zone, better filter performance, but more computational cost.
Lower order (fewer taps) → Wider transition zone, less precise filtering, but computationally cheaper.
