Hemodynamics

Question 1

blood flow

Answer 1

Q (L/min) = velocity * cross sectional area

A = pie r^2

Question 2

equation of continuity

Answer 2

system is closed amt of blood flowing is constant

Qa=Qb=Qc or vA=vA=vA

Question 3

Poiseulle’s equation

Answer 3

describes fluid flow through rigid pip

Q = (diffPpier^4) / (8lengthviscosity)

Question 4

relationship bet Q and P

Answer 4

Q is proportional to diff P

no pressure no flow = heart failure

Question 5

relationship bet Q and vessel radius

Answer 5

Q proportional to r^4
small change in dia = great change in flow
resistence arterioles
so, 2r = 16x inc in Q
and 1/2r = 16x dec in Q

Question 6

relationship bet vessel length and Q

Answer 6

Q proportional to 1/L
irrelevant bc w cant change it
greater dist = greater R = less flow

Question 7

relationship bet viscosity and Q

Answer 7

Q = 1/viscosity

more viscous greater resistance to flow

Question 8

life at high altitudes

Answer 8

inc hematocrit to comp for dec O2 availability

inc RBC -> inc viscosity = dec Q

Question 9

polycythemia vera

Answer 9

overproduction of red blood cells

increased viscosity decreased flow

Question 10

severe dyhydration

Answer 10

decrease of plasma

thus inc viscosity and dec flow

Question 11

sickle cell anemia

Answer 11

reduce pliability of RBCs - increase resistence, increase apparent viscosity , so decreases flow

Question 12

resistence in series

Answer 12

Rtotal= R1+R2+R3 etc

1+2+3=6

Question 13

resistence in parallel

Answer 13

decreases total R
change one R doesnt affect others or total R
Resistance is at resistance arterioles (capillaries don’t contribute)
1/Rtotal = 1/R1 + 1/R2 + 1/R3 etc
=o.55

Question 14

systemic vascular resistance (SVR)

total peripheral resistance (TPR)

Answer 14

sum of all resistances that lie bet aorta and vena cava
TPR/SVR = (mean art P - central venous P) / CO
normal; 15-18mmHg

Question 15

pulse pressure =

Answer 15

PP = SystolicBP - DiastolicBP

Question 16

mean arterial pressure =

Answer 16

MAP = DiastolicBP + (PP/3)

note; this is not an average bc the heart spends more time relaxed (2/3) than contracted (1/3)

Question 17

shock and TPR/SVR

Answer 17

most shock = Increase in TPR

septic shock = lrg Decrease in TPR

Question 18

cardiogenic shock

Answer 18

inc Preload, dec CO, inc SVR

Question 19

hypovolemic shock

Answer 19

dec Preload, dec CO, inc SVR

Question 20

distributive/septic shock

Answer 20

dec/normal Preload, and CO change, Dec SVR

Question 21

obstructive shock

Answer 21

inc Preload, dec CO, inc SVR

Question 22

pulmonary embolism shock

Answer 22

dec Preload, dec CO, inc SVR

Question 23

deviations from Poiseuille’s Law

Answer 23

1) laminar vs. turbulent flow
2) viscosity changes w velocity
3) compliance of blood vessels

Question 24

streamline/laminar flow

Answer 24

velocity center>velocity at edge
flow:pressure
fluid in middle flows the fastest

Question 25

turbulent flow

Answer 25

chaotic velocities (as velocity inc pattern becomes unstable and breaks down into turbulence)
flow : sqr root of Pressure
so, greater P require to push same amt of blood (to get same amt of Q)

Question 26

Reynolds number

Answer 26

dimensionless number analyzes flow through tubes
Nr > 2000 = turbulent flow

Nr = (veldiadensity) / viscosity

so ratio of;
inertial forces (disrupt laminar flow)
to, viscous forces (stabilize laminar flow)

Question 27

murmurs

Answer 27

the sounds of turbulent flow

Question 28

relationship between viscosity and velocity

Answer 28

viscosity - 1/velocity
low velocity gets gunky
speed up, breaks those interactions - less viscous (more like water)

Question 29

relationship of compliance

Answer 29

compliance = how much they dilate - the change in volume for a given pressure change
veins - highly compliant
= change in Vol / change in Pressure

Question 30

Poiseulles equation

Answer 30

Q = (diff P* pie * r^4) / (8 * length * viscosity)

fluid flow through a rigid pipe