Haemodynamics Flashcards
What is plasma?
Fluid collected from unclotted blood
so it includes clotting factors
What is serum?
Fluid collected from clotted blood
so it doesn’t include clotting factors
What is the relationship between plasma and serum?
Serum = plasma - clotting factors
What is blood flow?
Volume of blood per unit time through blood vessel
What are the factors affecting blood flow?
Difference in blood pressure
Resistance
What is blood pressure?
The force that is exerted on blood vessel walls by the blood
How does difference in blood pressure affect blood flow?
The bigger the difference in blood pressure
the more the blood flow
What direction of pressure does blood move in?
High pressure to low pressure
How does resistance affect blood flow?
As resistance increases
blood flow decreases
What is resistance?
Opposition to blood flow
What are the factors affecting resistance?
Length of blood vessel
Radius of blood vessel
Blood viscosity
How does the length of a blood vessel affect resistance?
As length of blood vessel increases
resistance increases
How does the radius of a blood vessel affect resistance?
As radius of blood vessel increases
resistance decreases
How does blood viscosity affect resistance?
As blood viscosity increases
resistance increases
What is peripheral resistance?
Total opposition to blood flow
offered by all the systemic vasculature
What is another term for total peripheral resistance?
Systemic vascular resistance
What type of blood vessel is mostly responsible for peripheral resistance?
Arterioles
How do arterioles change the peripheral resistance?
Vasoconstriction decreases their radius, which increases resistance
Vasodilation increases their radius, which decreases resistance
What is meant by whole blood viscosity?
How thick the blood is
What can cause a major increase in whole blood viscosity? Which is the most common cause?
Multiple myeloma - most common cause
Leukaemia
Thrombocythaemia
Polycythaemia
What component of blood does multiple myeloma affect? How is it affected?
Plasma
increases plasma viscosity
by increased number of immunoglobulins
What effect does an increase in whole blood viscosity have on blood in the peripheries? Why?
Sludging of blood in peripheries
as blood cools down in peripheries
What can cause a minor increase in whole blood viscosity?
Increased levels of acute phase proteins
What are three examples of acute phase proteins?
Complement proteins
C-reactive protein (CRP)
Fibrinogen
What causes an increase in acute phase proteins?
Inflammation
What are acute phase protein levels used to measure?
Inflammatory response
Which acute phase protein in particular is used to measure the inflammatory response?
CRP
What are the two types of blood flow?
Laminar flow
Turbulent flow
What is laminar flow?
Blood flowing in straight lines
remaining at same distance from vessel wall
Where is blood velocity greatest in laminar flow? Why?
In centre of vessel
because blood at peripheries comes into contact with vessel wall, increased friction, resistance to blood flow
What is turbulent blood flow?
Blood flowing in all directions in the vessel
mixing of blood within vessel
What are the causes of turbulent blood flow?
Blood velocity is too large
Blood passes over rough surface
Blood passes stenosis or obstruction in vessel
Blood passes a sharp turn
What is meant by stenosis of a blood vessel? And obstruction?
Stenosis means narrowing of blood vessel
Obstruction means complete blockage of blood vessel
What is it called when turbulence can be felt in a blood vessel?
Thrill
What is it called when turbulence can be heard in a blood vessel?
Bruit
What is it called when turbulence can be heard over a heart valve?
Murmur
What is blood velocity?
Speed of blood moving through blood vessel
What are the units of blood velocity?
Distance/time
What are the factors affecting blood velocity?
Blood flow
Cross-sectional area of blood vessel
How does blood flow affect blood velocity?
As blood flow increases
blood velocity increases
How does cross-sectional area of a blood vessel affect blood velocity?
As cross-sectional area of blood vessel increases
blood velocity decreases
How are blood flow and blood velocity affected distal to a stenosis? Why?
Stenosis decreases radius of blood vessel, which increases resistance, which decreases blood flow
Stenosis decreases cross-sectional area of blood vessel, which increases blood velocity
What blood vessel abnormality often forms distal to stenosis? What does it mean?
Aneurysm
refers to an abnormal dilation of a blood vessel
Why do aneurysms often form distal to a stenosis?
High blood velocity pushes on blood vessel walls
pushes them apart
How does systole affect blood velocity?
Causes rapid increase in blood velocity as heart ejects lots of blood
followed by rapid decrease as heart ejects less blood
How does diastole affect blood velocity?
Negative blood velocity
As blood enters peripheries, faces peripheral resistance, bounces back slightly
