Cardio Equations

Question 1

Cardiac Output (CO)

Answer 1

HR x SV

SV=EDV-ESV

Question 2

Flow (Q)

Answer 2

volume/time; velocity (v)= displacement / time

v=Q/A or Q=A x v

A=area

Question 3

La Place’s Law

Answer 3

T=PR (cylindrical vessel)

T=PR/2 (spherical vessel)

Question 4

Ohm’s Law

Answer 4

ΔP = F x R or

F = ΔP / R or

R= ΔP / F

F = flow, R= Resistance, ΔP= pressure difference

Question 5

3 Pressure Types

Answer 5

Driving pressure: difference between points in tube

Transmural pressure: difference between pressure inside vessel and outside vessel

Hydrostatic pressure: Horizontal- consistent pressure from gravity; Vertical- increased at bottom

Question 6

Pressure Difference across CV system

Answer 6

ΔP = LV - RA

Question 7

Compliance

Answer 7

Ca = dVa / dPa

Question 8

Bernoulli Effect

Answer 8

dynamic component of pressure will take away from the lateral pressures

Ptotal = P lat + P dyn where

P dyn = pv^2 / 2

P dynamic = outside flow, P lateral = inside vessel flow

Question 9

Resistance

Answer 9

R = 8 x n x l / π x r^4

Doubling r decreases R by factor of 16
Viscosity (n) altered by changing hematocrit (thickens blood)
Length usually constant

Question 10

Viscosity (n)

Answer 10

n = shear stress / shear rate

Question 11

Reynolds number (NR)

Answer 11

NR = pDv / n

p = density, D = diameter, v = velocity, n = viscosity

NR < 2000 laminar
NR 2000-3000 some turbulence
NR > 3000 turbulent

Question 12

Total Peripheral Resistance (TPR)

Answer 12

TPR = ΔP / CO

ΔP = P aorta - P veins

Question 13

Vessels in Series and Parallel

Answer 13

Series: R total = R1 + R2 + R3…

Parallel: R total = 1/R1 + 1/R2 + 1/R3….

Question 14

Fick’s Law of Diffusion

Answer 14

J = S x Px x ([C]o - [C]i)

J=flux per unit time
S = Surface Area
Px = capillary permeability to X
C = difference between capillary concentration in and out

Question 15

Hydrostatic Pressure

Answer 15

ΔP = (P c -P if)

If P c > P if, then fluid leaves capillary (filtration)
Factors affecting Pc: resistance, change in pressure US or DS, gravity, time and location

Question 16

Oncotic Pressure

Answer 16

Δπ = (π c - π if)

Helps retain fluid in vessel

Question 17

Net filtration pressure (NFP)

Answer 17

NFP = (P c -P if) - (π c - π if)

Arterial: +10 mmHg (+ = filtration)

Venous: - 8mmHg (- = absorption)

Question 18

Cardiac Cycle

Answer 18

Duration (s/bt) = 60 (s/min) / heart rate (bts/min)

Question 19

Fick Principle

Answer 19

Arterial - Venous difference * F = substance utilized

Whole body (CO) 
F = amount (x) used per unit time / A-V difference

Question 20

Ejection Fraction (EF)

Answer 20

EF = SV / EDV

Question 21

If Preload increases…

Answer 21

EDV increased, no change in contractility

SV increased, FS Law

PV Graph extends up and to the right

Question 22

If Afterload increases…

Answer 22

same as increase in aortic pressure

greater force to contract against, decreased SV

PV Graph’s left side will shift right and top will extend up

Question 23

If contractility increases…

Answer 23

preload and afterload remain same

EDV: no change, ESV: decreased

PV Graph will extend to left and slight extension up

Question 24

Mean Arterial Pressure (MAP)

Answer 24

Pa = Pd + 1/3(Ps - Pd)

Pa (arterial pressure)
Pd (diastolic pressure)
Ps (systolic pressure)

Question 25

Myocardial O2 Consumption (MO2C)

Answer 25

MO2C = coronary blood flow x (AO2 - VO2)

Question 26

Blood volume (BV)

Answer 26

BV = plasma volume x 100 / 100 - Hematocrit

OR

BV = plasma volume / 1 - Hematocrit

Question 27

ECF Osmolarity

Answer 27

ECF Osmolarity = 2[Na+]

ICF = 2/3 bw

ECF = 1/3 bw