7 Flashcards
whats normal BP
120 80 (16/10.7 kPq)
more than 140 is systolic marginal HT (lifestyle)
more than 160 is definite intervention threshold (drugs)
more than 90 is diastolic marginal HT (lifestyle)
more than 100 is definite intervention threshold (drugs)
Pulse Pressure
S-D
Mean Arterial Pressure
D plus 1/3 PP
whats the windkessel effect
the idea that arteries are elastic and so will distend as BP increases and will do elastic recoil when BP drops
whats classified prehypertension
120-139
or
80-89
stats about ppl w HyperT
30% of ppl who have it don’t know they do
40% of people who know they have it are not being treated
67% of those who are beingg treated don’t have it under control
whats Ohm’s law
ohm ferme pour rat
flow= Pressure/resistance
whats poseuilles law
the flow of a liquid though a tub will depend on the fourth power of the radius of the tube
so if you double radius, flow will increase by 2^4 so 16 times
what are the formula for CO
CO=Pressure/resistance but you cant measure resistance so
CO= HR x SV
measure HR with ECG measure SV using doppler
CO= cross section area of aorta x velocity of blood
how can you measure SV
doppler ultradoung
measures blood velocity through first part of aorta
measures cross section area of aorta.
non invasive good.
trasnoehsophagyl doppler
measures blood velocity through descending aorta
infers cross section area of aorta from nanogram using pt age and gender
go with probe inside trachea.
transthoraci impedance cardiogram
measures changes in electrical activity in thorax to infer SV using electrodes on thorax
unsure of accuracy
Normal CO value
5L/min
normal cross section area of aorta
10cm2
normal velocity
500cm per minute
what does preload affect
SV
how much can CO increase during exercise
about 4 times to reach 19L/min
HR can increase 2.5
SV can increase 1.5
what percentage of flow goes to kidney brain and heart
25%
14%
4%
what does resistance of capillaries depend on
hematocrit
diameter of capillary
normal hematocrits value
45%
hematocrits pathologies and values
between 60-70% is polycytheamia.
absolute if the cause is high number of RBC
relative is the cause if the drop in plasma.
capillary diameter
5 um
RBC diameter
up to 7 um
what prevents clots from forming in capillaries
when blood flow moves along it brushes against protein chains that protrude to the lumen. this action cauese the release of Ca inside the endothelium and NO formation. NO acts as a local antigcoahulatn
who’s more at risk for a stroke and why
ppl w atrial fibrillation bc of stagnant blood in auricles,
what is the end consequence of polycythemia
organ failure
what is laplace law.
the pressure that a tube can withstand depends on the tension on the walls and the diameter of the tube.
how come capillaries can withstand great pressure
bc their diameter is small
Pcan be withstood= tension on the walls/diameter
whats the most common site for an aneurysm
thoracic aorta
cerebral arteries because convoluted and twisted.
just before points where blood vessels branch out
1-8% inscidence.
atheromas cause turbulent flow which increases BP so increased risk
atheroma also cause local inflammation which causes weakening of walks
how can aneurysm be identified
incidentally during MRI
because of subarachnoid hemoorgahe
bc of symptoms
how are aneurysms managed
clipping it if its near the sruface
inserting a metal coil via carotid artery to stabilize it.
where can eddies and vortices occur
at branch points
