Haemodynamics Flashcards
What is serum?
Plasma minus the clotting factors (in particular fibrinogen)
What can a marked increase in plasma viscosity mean for the blood as a whole?
Increase in blood viscosity and slugging of blood in peripheries
What is the most common cause for increased plasma viscosity?
Multiple myeloma (cancer of the plasma cells)
What is an increase in red blood cells called?
Polycythaemia
What is an increase in red blood cells called?
Thrombocythaemia
What is an increase in white blood cells called?
Leukaemia
What can polycythaemia/thrombocythaemia/leukaemia all lead to?
Increased whole blood viscosity and sludging of blood in peripheries
What is used to measure inflammation?
C-reactive protein (CRP)
How can minor changes in plasma viscosity be used to measure inflammation?
Changes to plasma viscosity arise from raised levels of acute phase plasma proteins which increase in response to inflammation.
The two things are indirectly linked
What is the difference between laminar and turbulent flow?
Which flow type is typical for blood?
Laminar- straight lines
Turbulent- all directions
Laminar
When laminar flow occurs where does the blood have the greatest velocity? What kind of profile does this cause?
Centre of vessel
Parabolic profile
When might the blood flow in a turbulent manner? (5)
- blood flow too great
- passing an obstruction
- sharp turns
- passing over rough surfaces
- increased resistance to blood flow
How do we measure flow?
In terms of volume per unit time
How is blood fed into the coronary arteries?
Due to peripheral resistance, the elastic walls of the aorta stretch. Some blood is pushed back towards the heart and into the coronary arteries. This mechanism also causes the valves to snap shut
When does the pressure in the aorta increase during the cardiac cycle?
When the L ventricle ejects
Diagrammatically speaking what is the rise in pressure in the aorta pressure tracing called?
Anacrotic limb (caused by LV contraction)
Diagrammatically speaking what is the drop in pressure in the aorta pressure tracing called?
Dicrotic limb (LV relaxation)
There is a blip in the dicrotic notch when looking at the aortic pressure tracing, what is this called and what causes it?
Dicrotic notch
Point at which the aortic valve shuts
The shutting of the aortic valve signifies the end of what in the cardiac cycle?
Systole
What is pulse pressure? (How is it calculated)
(The peak systolic pressure)-(end diastolic pressure)=pulse pressure
Or more commonly: systolic pressure-diastolic pressue= 120-80=40mmHg
How can the mean arterial pressure be estimated?
Diastolic pressure + 1/3 of the pulse pressure
Roughly: 80 + 13 = 93mmHg
Is the MAP falls below 70mmHg what is said to be impaired?
Organ perfusion
At the beginning of diastole, what kind of flow is common particularly in the arterial peripheries? And why?
Retrograde flow (reverse flow) Due to peripheral resistance- blood 'bounces back'
If there is a constriction in a vessel, where is the pressure greatest?
Before the obstruction
When there is a constriction in a vessel what happens to rate of flow?
It decreased after the constriction
When there is a constriction in a vessel what happens to the velocity of the blood?
It is increased after the constriction
What is a narrowing in an artery called?
A stenosis
When there is a stenosis in an artery, what happens to the distal flow?
It is decreased
When there is a stenosis in an artery, what happens to the distal velocity?
It increases
What do you call an enlargement of an artery?
Aneurism
As we get older what can happen to our arteries and what effect does this have on the pulse?
They calcify
Th pulse cannot be felt as well
When you feel an artery with a stenosis in what do you feel, how do you describe this?
Turbulence in blood flow
Called a thrill
When listening with a stethoscope to an artery with a stenosis, there is an abnormal sound created by turbulent flow, what is this sound called?
A bruit
What two things effect the strength/volume of the pulse?
- force of LV ejecting blood
- pulse pressure
What does a greater pulse pressure mean?
There is a stronger bulse- bounding
What can cause a reduce pulse strength/volume causing a thread pulse? (3)
LV failure
Aortic valve stenosis
Hypovolaemia (severe hydration, bleeding)
How can bradycardia lead to a bounding pulse?
It widens pulse pressure therefore pulse felt is stronger
Dicrotic limb is extended
What effect does a lower peripheral resistance have on the diastolic pressure?
It lowers it
Why do pregnant women often have lower BP?
Because the foetus produces lots of heat and it needs to be gotten rid of through vasodilation- lowers peripheral resistance, causing a lower diastolic pressure
How does low peripheral resistance causes a bounding pulse?
It lowers diastolic pressure- widens pulse pressure- pulse volume= increased
Why is it important to use the correct size cuff when taking BP?
Too small a cuff= too high a BP
