Pressure and Flow in Arteries Flashcards
How can you measure arterial pressure?
By inserting an arterial line (thin catheter) into an artery
When measuring arterial pressure, where would you usually insert the arterial line (thin catheter)?
Radial artery at the wrist
or
Brachial artery at the elbow.
What are the advantages and disadvantages of using an arterial line?
Advantages- continuously measures BP, very accurate
Disadvantage- invasive
As using an arterial line is invasive, how would we usually measure someone’s arterial pressure?
Auscultation of Korotkoff sounds using a sphygmomanometer and stethoscope
What are the advantages and disadvantages of using Korotkoff sounds?
Advantages- non-invasive, cheap
Disadvantages- discontinuous, less accurate, requires skill and care.
Auscultation?
Listening w a stethoscope
What are Korotkoff sounds?
Turbulent blood flow
What does a sphygmomanometer measure?
BP
When using a sphygmomanometer, what will you here on the brachial artery before inflating the cuff?
Nothing as there is no turbulent blood flow.
What do you hear when you inflate the cuff to beyond systolic pressure?
You hear nothing as you completely occlude the vessel so no turbulent blood flow.
When will you start to hear Korotkoff sounds?
When the pressure in the cuff falls below systolic pressure as blood starts flowing back into the artery
What is the pattern of sounds you will hear in your stethoscope when manually taking blood pressure?
Silence -> Tapping -> Thumping -> Muffled -> Silence
What is the point at which you first hear the tapping sound known as?
Systolic blood pressure
What is the point where the sounds completely disappear known as?
Diastolic blood pressure.
What are oscialltions?
Vibrations generated from turbulent blood flow.
Do automatic machines measure Korotkoff sounds or oscillations?
Oscillations
Describe some of the advantages and disadvantages of using Oscillatory blood pressure measurement.
Advantages- non-invasive, cheap, easier to use
Disadvantages- discontinuous, accuracy, needs care
What happens to the aorta when the left ventricle contracts during systole?
Blood is ejected into the aorta and the walls of the aorta stretch.
Aorta acts as a pressure reservoir.
What happens to the aorta during diastole?
Elastic recoil from the walls of the aorta which pushes on the blood and closes the aortic valve.
What is the pressure wave affected by?
Stroke volume
Velocity of ejection
Elasticity of arteries
Total peripheral resistance
What is the value of normal arterial pressure?
120/80
What happens when the aorta acts as a pressure reservoir?
Damps down pressure variations
What can cause arteries to lose their elasticity?
Age
What is the effect of arteries losing their elasticity?
Systolic pressure will rise
Diastolic pressure will fall
What happens to arterial pressure overall with age?
It increases
->elderly more likely to have hypertension etc.
What happens to pressure throughout the vascular tree?
It drops
Quantify the drop in pressure as blood travels through the artery
Small drop… from 95 to 90 mmHg
Quantify the drop in pressure as blood travels through the arterioles.
Large drop (from ~90 to 40 mmHg)
Therefore, what is pressure like when the blood reaches the arteries?
Is this good or basd?
Low bp
Good as very thin walls
What pressure is the blood when it reaches the venules?
About 20 mmHg
What happens to the bp when the blood goes into the right atrium?
Drops to about 5 mmHg
Which system requires a lower BP for blood to be pumped- systemic or pulmonary?
Pulmonary
Where is velocity high?
In the aorta
What happens to velocity as blood travels through the arteries and arterioles?
It decreases
What happens to velocity when blood reaches the vein and venules?
It increases
What is velocity related to?
Cross-sectional area
Why is velocity fastest in the aorta?
Small cross-sectional area so has to be quick to get all the blood through
Where is velocity slowest?
Capillaries
