hemodynamics

Question 1

1. how is the velocity of bloodflow related to the cross sectional area of a blood vessel or group of vessels?

Answer 1

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)

Question 2

2. according to ohms law, what 2 factors determine blood flow through a blood vessel.

Answer 2

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

Question 3

3. define blood pressure

Answer 3

force exerted by the blood against any area of the vessel wall

Question 4

4. what is the conversion factor from mm-Hg(mercury) to cm-H20.

Answer 4

1mmHg = 1.36cm H20

Question 5

5. what is cerebral perfusion pressure

Answer 5

MAP- (CVP or ICP) whichever is higher. CPP is gradient for driving flow across brain

Question 6

6. what is poiseulle’s law?

Answer 6

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

Question 7

7. according to poiseulle’s law, what factor has the greatest impact on the rate of blood flow through a vessel?

Answer 7

RADIUS of vessel- doubling radius of tube causes 16 fold increase in flow

Question 8

8. what is resistance?

Answer 8

impedence to blood flow in a vessel- SVR and PVR (Ohms Law)

Question 9

9. can resistance be measured directly

Answer 9

No- must be calculated- SVR and PVR

Question 10

10. what is the formula for calculating SVR

Answer 10

MAP-CVP/COx80

Question 11

11. what is formula for calculating PVR

Answer 11

MPAP-PCWP/COx80

Question 12

12. how would you calculate resistance when blood vessels are arranged in a series

how would you calculate resistance when vessels are arranged in parallel

Answer 12

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…

Question 13

13.if you added another blood vessel in a parallel arrangement would total vascular resistance increase or decrease and why?

Answer 13

TVR would drop when you add another part because increase radius has profound effect, expanded cross sectional area

Question 14

14.what is laminar flow?

Answer 14

smooth efficient flow

Question 15

15.what is turbulent flow?

Answer 15

colliding, all over the place, inefficient flow

Question 16

16.what formula could you use to predict laminar vs turbulent flow?

Answer 16

Reynolds number 3000 turbulent

Question 17

17.what is relationship of hematocrit to blood viscocity?

Answer 17

as HCT increases, viscosity increases

Question 18

18. as BP increases within a vessel why does blood flow increases much greater than one would expect?

Answer 18

as diameter increases, vessels are distensible, pressure up, flow up tremendously

Question 19

19 (1). what is most important monitor in OR

Answer 19

YOURSELF!

Question 20

20(2). name a return-to-flow technique of BP measurement

Answer 20

palpation, pulse ox, indwelling arterial catheter

Question 21

21(3). name several insertion sites for arterial catheters

Answer 21

radial, brachial, femoral, dorsalis pedis, axillary, ulnar

Question 22

22(4). in healthy individual with disease-free arteries, does SBP increase or decrease in leg relative to proximal aorta

Answer 22

increase

Question 23

23(5). what is damping

Answer 23

undershoot of diastolic, overshoot of systolic- like bridge that collapsed

Question 24

24(6). what is ringing

Answer 24

exaggerated waveform 40-50 above

Question 25

25(7). what are 3 waves of CVP

Answer 25

a- contraction, c- isovolumic contraction, v- tricuspid open, filling

Question 26

26(8). what are different waveworms that would be encountered when inserting a S-G from RIJ to PA

Answer 26

CVP, RAP, PAP, wedge

Question 27

27(9). what info can be gathered from SG

Answer 27

CO, CI, SV02, temp, PA pressures

Question 28

28(10). what steps would you take to inflate a PA catheter

Answer 28

slow, 1.5 cc air, watch monitor, stop with resistance, slow deflation

Question 29

29(11). 2 steps to zero a transducer

Answer 29

opening and leveling

Question 30

30(12). Fick principle of measuring CO

Answer 30

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

Question 31

31(13) thermodilution method of measuring CO

Answer 31

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