Haemodynamics Flashcards
What is the difference between plasma and serum?
Plasma is fluid collected from unclothed blood whereas serum is the fluid collected from clotted blood
What is the most common cause of increased plasma viscosity?
Multiple myeloma
What is the name given to an increase in red blood cells?
Polycythaemia
What is the term given to an increase in platelet levels?
Thrombocytosis
What is the name given to increased white blood cells?
Leukaemia
Increased RBCs, platelets and WBCs can all lead to what?
Increased whole blood viscosity and sludging of blood in peripheries
How can MINOR changes in plasma viscosity occur?
Give three examples
Raised levels of acute phase proteins
e.g. Fibrinogen
Complement factors
CRP (c-reactive protein)
What substance can be used clinically as a measure of inflammation?
C-reactive protein (CRP)
What is the difference between laminar and turbulent flow?
Laminar:
Streamline flow of blood with each layer remaining the same distance from the blood vessel wall
Turbulent:
Blood flowing in all directions in the vessel and continually mixing as a result of an obstruction, increased resistance, the rate of blood flow being too great
What causes a pulse?
The shock wave produced by distension of the aortic wall and the compliment vessels it then travels down. It arrives slightly before the blood itself
What is the difference between the flow and the velocity of blood?
The flow is the movement of a volume of blood over time whereas the velocity is the distance moved by an object over time
When laminar flow occurs, where in the vessel is the velocity of blood the greatest?
In the centre of the vessel compared to the outer edge, creating a parabolic profile
A strong pulse is often described as what?
“Bounding”
Reduced pulse volume can result from what?
Left ventricular failure
Aortic valve stenosis
Hypovolaemia
Reduced pulse volume is often described as what?
“Thready”
What does bradycardia do to the pulse pressure and how does this relate to the pulse that is felt?
It widens pulse pressure and leads to a bounding pulse
How does lowering peripheral resistance affect diastolic pressure and pulse pressure?
It lowers diastolic pressure
Therefore increasing pulse pressure
Name three things that lower peripheral resistance?
Hot bath
Exercise
Pregnancy
Serum = plasma - _______________
Clotting factors (fibrinogens)
What kind of profile does laminar flow produce?
Parabolic profile
What can cause turbulent flow in a blood vessel?
Sharp turn
Rough surface
Increased resistance to blood flow
Pulse pressure= ___________-_____________
Systolic pressure - Diastolic pressure
What is an general, average measurement of pulse pressure?
40mmHg
Mean arterial pressure is measured how?
Diastolic pressure + 1/3 Pulse pressure
Below what value is mean arterial pressure (MAP) considered to impair organ perfusion?
MAP below 70mmHg
Retrograde flow of blood in the arterial system is greatest when what feature is high?
Resistance
If the blood vessels lose their compliancy they cannot do what?
What might be a cause of this?
Transmit a shock wave, no pulse will be felt
Caused by calcification of the arterial wall
Resistance vessels are found on which side of the circulatory system?
Arteriolar side (arterioles)
What is the role of resistance vessels in the circulatory system?
To restrict blood flow to drive supply to areas of the body that are hard to perfuse
On which side of the circulatory system are capitance vessels found?
The Venous return side
What is the role of capitance vessels within the circulatory system?
To enable the system to vary the amount of blood pumped around the body
The circulation acts as two pumps in series, what are these two pumps?
How does the pressure within these two pump system vary?
The systemic circulation (high pressure)
The pulmonary circulation (low pressure)
Systole is what?
Contraction and ejection of blood from the ventricles
Diastole is what?
Relaxation and filling of the ventricles
What is the usual value for stroke volume for each ventricle?
Given this value, what is the amount of blood pumped by the heart in a minute?
Around 70ml per beat
@ 70bpm, amount pumped in 1 minute= 5L of blood
Describe the structure of cardiac muscle and how it compares to other muscle types
Specialised, striated muscle made up on individual cells (cardiac myocytes)
Somewhere between skeletal and smooth muscle
How do cardiac myocytes communicate with each other?
They are interconnected electronically by gap junctions
How does the action potential across the membrane of cardiac myocytes differ from action potentials in other cells?
Why is this the case?
The AP is longer in cardiac myocytes (around 280ms)
One AP is driving one beat of the heart, needs to be long enough to sustain the beat
What determines whether the valves of the heart are open or closed?
The difference in pressure across the valves
What structures prevent the inversion of valves on systole?
What are these structures connected to to give them their strength?
Chordae Tendineae
Papillary muscles
