hemodynamics Flashcards
- how is the velocity of bloodflow related to the cross sectional area of a blood vessel or group of vessels?
velocity is inversely proportional to the cross-sectional area. same flow all 3 points, velocity changes. capillaries- large cross sectional area (less velocity). aorta- small cross sectional area (large velocity)
- according to ohms law, what 2 factors determine blood flow through a blood vessel.
pressure gradient and resistance.
resistance same, increase pressure gradient = incr. flow
top same, resistance increases= decrease flow.
flow directly proportional to difference in pressure gradient
- define blood pressure
force exerted by the blood against any area of the vessel wall
- what is the conversion factor from mm-Hg(mercury) to cm-H20.
1mmHg = 1.36cm H20
- what is cerebral perfusion pressure
MAP- (CVP or ICP) whichever is higher. CPP is gradient for driving flow across brain
- what is poiseulle’s law?
flow is directly proportional to pressure gradient. flow is inversely proportional to length of tube. as radius is doubled, flow increases by 16 fold.
squeeze bag or raise IV bag- increase gradient.
increase tube length= decrease flow
- according to poiseulle’s law, what factor has the greatest impact on the rate of blood flow through a vessel?
RADIUS of vessel- doubling radius of tube causes 16 fold increase in flow
- what is resistance?
impedence to blood flow in a vessel- SVR and PVR (Ohms Law)
- can resistance be measured directly
No- must be calculated- SVR and PVR
- what is the formula for calculating SVR
MAP-CVP/COx80
- what is formula for calculating PVR
MPAP-PCWP/COx80
- how would you calculate resistance when blood vessels are arranged in a series
how would you calculate resistance when vessels are arranged in parallel
they become additive- adds length, adds resistance
Rtotal= R1+R2+R3+R4…
resistance drops when you add another piece
1/Rt= 1/R1 + 1/R2 + 1/R3…
13.if you added another blood vessel in a parallel arrangement would total vascular resistance increase or decrease and why?
TVR would drop when you add another part because increase radius has profound effect, expanded cross sectional area
14.what is laminar flow?
smooth efficient flow
15.what is turbulent flow?
colliding, all over the place, inefficient flow
16.what formula could you use to predict laminar vs turbulent flow?
Reynolds number 3000 turbulent
17.what is relationship of hematocrit to blood viscocity?
as HCT increases, viscosity increases
- as BP increases within a vessel why does blood flow increases much greater than one would expect?
as diameter increases, vessels are distensible, pressure up, flow up tremendously
19 (1). what is most important monitor in OR
YOURSELF!
20(2). name a return-to-flow technique of BP measurement
palpation, pulse ox, indwelling arterial catheter
21(3). name several insertion sites for arterial catheters
radial, brachial, femoral, dorsalis pedis, axillary, ulnar
22(4). in healthy individual with disease-free arteries, does SBP increase or decrease in leg relative to proximal aorta
increase
23(5). what is damping
undershoot of diastolic, overshoot of systolic- like bridge that collapsed
24(6). what is ringing
exaggerated waveform 40-50 above
25(7). what are 3 waves of CVP
a- contraction, c- isovolumic contraction, v- tricuspid open, filling
26(8). what are different waveworms that would be encountered when inserting a S-G from RIJ to PA
CVP, RAP, PAP, wedge
27(9). what info can be gathered from SG
CO, CI, SV02, temp, PA pressures
28(10). what steps would you take to inflate a PA catheter
slow, 1.5 cc air, watch monitor, stop with resistance, slow deflation
29(11). 2 steps to zero a transducer
opening and leveling
30(12). Fick principle of measuring CO
CO= 02 per min absorbed by lungs mL/min divided by
AV difference mL/L of blood
R heart 160mL/L– CO 5L/min - 02 used 200mL/min— L heart 200mL/L
31(13) thermodilution method of measuring CO
passing cold fluid- lot of blood flow there is small temp change- HIGH CO- small area under curve
low bloodflow, big temp change- LOW CO- big area under curve
