hemodynamics Flashcards
as cross sectional area increases, velocity
increases
olm - what two factors determine blood flow thru vessel
voltage diff and resistance. (PressureArterial - pVenous) / resistance.
according to olm, increasing resistance ___ flow
decreases
according to olm, increasing resistance ___ pressure
increases
define BP
the force exerted by the blood against any unit area of the vessel wall
conversion factor from mmHG to cmH20
1mm=1.36cm h20 pressure
cerebral perfusion pressure
MAP - CVP or ICP (whichever is higher)
what dose poiseullies law talk about
flow
according to poissuellie, flow is ___ proportional to the pressure gradient
directly
according to possueille, flow is ____ proportional to the radius
directly
according to poiseuillie, flow is INDIRECTLY porportional to
viscosity and length
***according to poiseulles law what factor has the greatest impact on the rate of blood flow thru a vessel
radius to 4th power
if radius is tripled,
64 fold
can resistance be measured directly
no
SVR formula
MAP-CVP/ CO x 80
PVR
MAP-PCWP / CO x 80
blood vessels in series =
r1+r2+r3..
blood vessels in parallel =
1/r1 + 1/r2 + 1/r3
flow thru each of the parallel vessels is determined by
the pressure gradient and its own resistance
if you add another blood vessel what happens to total vascular resistance
decreases
laminar flow is most related to
viscosity
turbulent flow is most related to
density
laminar flow - blood near vessel wall is ___, blood in middle is ___
slow, fast
what formula predicts laminar vs turbulent
reynolds. when its above 2000, turbulence usually occurs
reynolds number formula
(density x tube diameter x mean velocity) / viscosity
increasing hematocrit ____ viscosity
increases
reduced hematocrit causes low viscosity, which causes ____ turbulence
high. because viscosity is indirectly related to reynolds number
higher viscosity , ___ reynolds #
lower.. double check this
as blood pressure increases within a vessel.. why does FLOW increase much greater than one would expect?
because of DILATION (arterial resistance down) and sympathetic stiumulation (increasing pa-pv gradient)
flow takes the path of
least resistance.
whats a predictor of when laminar flow becomes turbulent?
reynolds #
