Haemodynamics Flashcards
What is the difference between plasma and serum?
The fluid collected from unclotted blood is called plasma
The fluid collected from clotted blood is called serum.
Serum has plasma and clotting factors (in particular fibrinogen)
In what diseases does whole blood viscosity occur?
Multiple myeloma is the main cause of whole blood viscosity.
This is because the protein content increases.
Leukaemia -increase in white cells
polycythaemia -Increase in red blood cells
thrombocythaemia - Increase in platelets
can all also cause whole blood viscosity
What is the difference between plasma viscosity and whole blood viscosity?
Minor changes in plasma viscosity can result from raised levels of acute phase plasma proteins (eg fibrinogen, complement factors and C-reactive protein) which are released in response to inflammation.
Whereas, whole blood viscosity is a lot more serious.
What is used to ‘measure’ inflammation?
Minor changes in plasma viscosity can be used to ‘measure’ inflammation because the level of acute phase proteins in the blood rises with inflammation. In recent years, we have been able to measure the levels of CRP (C-Reactive Protein) to ‘measure’ inflammation.
What is the difference between laminar and tubiland flow?
Laminar - Blood flows in streamlines with each layer of blood, remaining the same distance form the wall.
When laminar flow occurs, the velocity of the blood in the centre of the vessel is greater than towards the other edge. This creates a parabolic effect.
Turbulent - blood flow in all directions and continually mixing within the vessel.
What causes turbulent flow?
Turbulent flow occurs when:
- The rate of blood flow becomes too great
- It passes an obstruction in a vessel
- It makes a sharp turn
- It passes over a rough surface
- Increased resistance to blood flow
How do you measure flow?
Volume per unit time
What is a rise in pressure called?
Anacrotic limb. This occurs during systole.
What is it called as pressure decreases?
Dicrotic limb. This occurs during diastole.
What causes the dicrotic notch?
The closing of the aortic valve
What is pulse pressure?
Pulse pressure = peak systolic pressure - end diastolic pressure
This is equal to
systole pressure - diastolic pressure because of the way we measure BP with a sphygmomanometer.
So, most commonly pulse pressure is 120mm/Hg - 80mm/Hg = 40mm/Hg
What is the mean arterial pressure?
It can be estimated as diastolic pressure + 1/3 of the pulse pressure.
Therefore, most commonly, mean arterial pressure is 80mm/Hg + 13mm/Hg = 93mm/Hg.
If the mean arterial pressure falls below 70mm Hg then organ perfusion is impaired.
What is a stenosis? What happens to velocity at this point?
A stenosis is the narrowing of the artery. Velocity will increase at the point of stenosis
What happens to velocity, pressure, energy and flow after a stenosis?
After stenosis, velocity will increase,
Flow will decrease,
Pressure will decrease,
energy will increase
What do we feel when were feeling a pulse?
We feel a shock wave that arrives slightly before the blood itself.