Exam 1 FORMULAS

Question 1

Clearance

Answer 1

C(x) = [U(x) * V̇] / P(x)

Question 2

GFR

Answer 2

GFR= [U(creatinine) x V̇]/P(creatinine)

Question 3

Calculating MAP

Answer 3

MAP = DBP + 1/3 (SBP-DBP)

Question 4

Pulse Pressure

Answer 4

SBP - DBP

Question 5

Compliance

Answer 5

C= ΔV/ΔP

Question 6

Distensibility

Answer 6

ΔV/[ΔP * Original Volume]

Question 7

Conductance (BLOOD FLOW) and relationship to diameter

Answer 7

Conductance ∝ Diameter ^4

Question 8

If we have a pressure gradient (ΔP) of 50 mmHg with a blood flow of 100 mL/min, what would be the new flow if the radius (or diameter) were to increase x2? Assume vessel length and the pressure gradient were to remain constant.

Answer 8

100 mL/min
Diameter increases by 2 (two times the original diameter)
2^4 = 16
100 mL/min * 16 = 1600 mL/min of blood flow with a doubled diameter

Question 9

If we have a pressure gradient (ΔP) of 50 mmHg with a blood flow of 100 mL/min, what would be the new flow if the radius (or diameter) were to decrease in half? Assume vessel length and the pressure gradient were to remain constant.

Answer 9

100 mL/min
Diameter decreases by half (0.5 times the original diameter)
0.5^4 = 0.0625
100 mL/min * 0.0625 = 6.25 mL/min of blood flow with a diameter reduced by half

Question 10

Poiseulle’s Equation

Answer 10

• He didn’t teach this equation per se, he did include Guyton review questions that covered this so I would memorize it!
• Q = flow
• η = viscosity
• l = pipe (vessel length)

Question 11

Conductance (in relation to resistance)

Answer 11

Conductance = 1/resistance

• There is an INVERSE relationship between the two

Question 12

Ohm’s Law

Answer 12

ΔP = F x R

Question 13

Calculating vascular resistance in mmHg/L/min

Answer 13

R= ΔP/F

or

R= (MAP-CVP)/CO

Question 14

Velocity of flow

Answer 14

V= F/A

A= cross-sectional area

Question 15

Reynold’s Number

A number greater than ____ indicates turbulent flow.

Answer 15

Re = (V * d * p) / η

V= velocity
d= diameter
p = density
η= viscosity

2,000

Question 16

Cardiac Index

Answer 16

(SV*HR)/BSA

BSA = body surface area (m^2)

Question 17

What’s the average BSA for a 70kg adult?

Answer 17

1.7 m^2

Question 18

SVR

Answer 18

[(MAP-CVP)/CO] * 80

Question 19

What are the two units we may use for SVR?

Answer 19

cgs (centimeters, grams, seconds) or dynes*sec/cm^5

Question 20

Peripheral Resistance Unit (PRU)

Answer 20

ΔP/flow

*** flow is calculated in mL/sec, NOT L/min

Question 21

What is the conversion factor to convert PRU’s into cgs or dynes*sec/cm^5?

Answer 21

Multiply PRU’s by 1333

Question 22

Resistance to Venous Return (RVR)

Answer 22

(mPsf-RAP)/C.O.

*this was from the Guyton review book. Units are mmHg/L/min. Can simply multiply by 80 and it should give you the answer in cgs if the Prophet Schmidt asks for it

Question 23

Venous Return

Answer 23

(mPsf-RAP)/RVR

Question 24

Pulmonary Vascular Resistance

Answer 24

[(mPAP-PAWP)/C.O.] * 80

Question 25

What is a normal cardiac index in a 70 kg patient?

Answer 25

5L/min / 1.7m^2 = 2.9 L/min/m^2 About 3 L/min/m^2

Question 26

Renal Blood Flow

Answer 26

Renal Plasma Flow/ 1-Hct

Question 27

Laplace Law

Answer 27

T= Pr/w T= tension (ventricular wall tension) P= systolic BP r= ventricular radius w= ventricular wall thickness