CVT 100 #3 &4 Hemodynamics

Question 1

Flow requiresa

Answer 1

difference of energy, an energy gradient,usually apparent to us asa difference of pressure:DP

Question 2

What does the aortic walls do during Systole?

Answer 2

aortic walls expand and store energy

Question 3

What does the aortic walls do during Diastole?

Answer 3

aortic walls rebound, propelling blood distally to systemand keeping pressure up during diastole

Question 4

Aortic valve also keeps aortic pressure from

Answer 4

falling to zero by preventing backflow into LV

Question 5

There are pressure drops throughout the circulatory system—

Answer 5

there must be DPfor flow to occur

Question 6

Assessing valvular stenosis

Aortic stenosis

Answer 6

• Measure velocity at systole
• Measure pressure in LV and Ao
• Increased pressure in LV

Question 7

Assessing valvular stenosis

MV stenosis

Answer 7

• Measure velocity at diastole
• Measure pressure in LA and LV
• Increased pressure in LA

Question 8

LE segmental pressure measurements

Answer 8

Put 4 cuffs on each leg
Get systolic pressures using Doppler
Look for significant pressure gradient
   between adjacent cuffs: >20-30 mmHg
A significant gradient suggests stenosis 
   BETWEEN   the cuffs

Question 9

Claudication:

Answer 9

pain with exercise,
relieved by rest

Usually calf, possibly progressing to thigh, hip, buttock

Question 10

Should the pressures on either side of the MV be different?

Answer 10

When the mitral valve is open, the pressure should be the same on both sides.A pressure gradient across the valve suggests mitral stenosis.(Common cath lab procedure)

Question 11

Jean Léonard Marie Poiseuille

Answer 11

Investigated relationships of factors involved with fluid flow
through tubes.

Question 12

Poiseuille’s Law

Answer 12

Factors involved in
steady laminar flow of
Newtonian fluid (i.e., water)
through rigid tubes

Question 13

Differences betweenlab and human body flow:

Answer 13

Steady flow vs. pulsatile flow

Newtonian fluid vs. blood

Rigid tubes vs. distensible arteries

Question 14

FLOW is Defined as

Answer 14

volume per unit time.
e.g., L/min, cc/hour, mL/min
etc.

(“Flow rate” is from the
Department of Redundancy Department.)

Question 15

The basic flow equation:

Answer 15

Q = DP
R

R = DP DP = Q x R
Q

Question 16

Q is

Answer 16

flow

Question 17

R is

Answer 17

resistance the force opposing flow

Question 18

DP is

Answer 18

the pressure gradient.

Question 19

How does flow work in the body?

Answer 19

The heart pumps ≈ 5 L/min.
Body tries to keep Q constant.
Heart can pump harder: increase DP
or
Body can tinker with peripheral resistance (vasomotor state): 
decrease R

Question 20

Cardiac cath lab (or ICU):

Answer 20

Determine cardiac output (Q)
Determine mean arterial pressure (P)
Find systemic vascular resistance: R = P
Q
(Can find pulmonary vascular resistance too)

Question 21

UNITS for
Pressure:

Flow:

Resistance:

Answer 21

Pressure: dyne/cm2

Flow: cm3/sec

Solve for R unitsbyMultiplying the numerator and the denominator by the inverse of the denominator:

Question 22

Resistance: What are the factors?
(Poiseuille again)
i.e., What influences resistance?

Answer 22

Length
Viscosity
Radius

Question 23

The resistance equation:

Answer 23

R = 8 L h
π r4

L = length       
h = viscosity
r = radius

Question 24

The powerful influence:radius (due to that power of 4)

Answer 24

Cut radius in half,
you get 16x the resistance.
Double the radius,
you get 1/16 the resistance

Question 25

Why 16 in regards to radius?

Answer 25

Double radius is x2
Take that doubling to the 4th power:
2x2x2x2 = 16
(Or 1/16 if you cut radius in half)

Triple the radius? Flow up 3x3x3x3,
or 81 times.

Question 26

Substitute the resistance factors in the simple flow equation and you get the big Poiseuille’s equation:

Answer 26

Q = DP π r4

8 L h

Question 27

What happens to flow if you double length or viscosity?

Answer 27

You cut flow in half.
Inverse relationship.
(Below the veeblefetzer)

Question 28

What happens to flow if you double the DP?

Answer 28

You double the flow.
Direct relationship.
(Above the veeblefetzer)

Question 29

What happens to flow if you double the radius?

Answer 29

It’s r to the 4th power:

24 = 2x2x2x2 = 16

Flow increases x 16:
very powerful relationship.

Question 30

What if you increase the radius x4?

Answer 30

4 x 4 x 4 x 4 = 256!

Question 31

And what if you increase the radius x10?

Answer 31

10 x 10 x 10 x 10 =
104 =
10,000!!

Question 32

Radius is implications for

Answer 32

1. vasomotor control of resistance
2. collaterals
3. those great big needles atthe blood bank

Question 33

In the human body, which factors are constant, and which variable?

Answer 33

Q = DP π r4

8 L h

Question 34

Calculate systemic vascular resistance:

Answer 34

CO = 5 L/min

MAP = 100 mmHg
RA = 10 mmHg

THE UNITS OF THE ANSWER
WILL BE….?

Question 35

MAP-RA = P1 - P2

Answer 35

100 - 10 = 90 mmHg for DP
across the systemic circulation

R = DP
Q