Formulas and Equations

Question 1

Modified Bernoulli equation

Answer 1

Pressure = 4(Vmax)^2

Question 2

Cardiac output
MAP
SVR
PVR

Answer 2

CO = SV x HR
MAP = CO x SVR or [(DBP x2) + SBP]/3
SVR = [MAP-CVP/CO] x80
PVR = [(10)(TR peak velocity)/RVOT VTI] + 0.16 or [(80)(mPAP - PCWP)/CO]

Question 3

RAP estimate based on IVC size and collapsibility

Answer 3

< 2.1 cm and > 50% = 3
< 2.1 cm and < 50%, or > 2.1 cm and > 50% = 8
> 2.1 cm and < 50% = 15

Question 4

RVSP

Answer 4

RVSP = RAP + 4x(TRmax)^2
RVSP = SBP - 4x(VSDmax)^2

RVSP = sPAP if no pulmonic stenosis

If PS, then sPAP = RVSP - 4x(PSmax)^2

Question 5

mPAP, dPAP, and RVEDP

Answer 5

mPAP = RAP + 4x(PRmax)^2, or
mPAP = 1/3 sPAP + 2/3 dPAP

dPAP = RAP + 4x(PRend-diastolic velocity)^2

RVEDP = LVEDP - 4x(VSDdiastolic velocity)^2

Question 6

PVR

Answer 6

PVR = [(10)(TRmax)/RVOT VTI] + 0.16, or
PVR = [(80)(mPAP - PCWP)/CO]

Question 7

LAP

Answer 7

LAP = E/e' + 4, or
LAP = SBP - 4x(MRmax)^2, or
LAP = 1.24 x E/e' + 1.9

Question 8

LVSP

Answer 8

LVSP = 4(MRmax)^2 + LAP

LVSP = SBP

Question 9

LVEDP

Answer 9

LVEDP = DBP - 4(AR end diastolic velocity)^2

Question 10

Stroke volume formula from VTI

Answer 10

SV = CSA (cm2) x VTI (cm) = volume (cm3)

Question 11

PISA area

PISA flow

Answer 11

PISA area = 2pir^2

PISA flow = PISA area x Valiasing

Question 12

EROA

Regurgitant volume

Answer 12

EROA = Qpisa/MRvmax

RVol = EROA x MR VTI

Question 13

Continuity equation

Dimensionless index

Answer 13

A1V1 = A2V2, Area1 = (Area2)(VTI2)/(VTI1)

DI = LVOT VTI/AV VTI

Question 14

MVA derived from PHT and deceleration time

Answer 14

MVA = 220/PHT

MVA = 759/DT

Question 15

PHT calculation for MS

Answer 15

PHT = 0.29 x DT

Question 16

Oxygen content

Delivery of O2

Answer 16

CaO2 = (1.39 x Hgb x SaO2) + (.003)(PaO2)

DLO2 = CO (1.39 x Hgb x SaO2) + (.003)(PaO2)

Question 17

Fractional shortening

Answer 17

(LVIDd - LVIDs)/LVIDd

Question 18

Wavelength
Velocity
Frequency

Answer 18

V=fλ

f=v/λ

λ=v/f

Question 19

Period

Power

Intensity

Answer 19

Period = 1/frequency

Power = joules/sec = watts

Intensity = Power/area

Power and intensity proportional to amplitude^2

Question 20

Formula for velocity at 1/2 max pressure (used for PHT)

Answer 20

v = (P/4)^1/2

When using PHT; pressure is 50% max pressure, but velocity is 70% max velocity

Question 21

Doppler shift equation

Answer 21

Doppler shift = (V cosΘ 2FT)/(C)

V = blood flow velocity
FT = transmitted frequency
C = 1540 m/s
Cos 0 = 1
Cos 90 = 0

Question 22

Speed of sound in tissue? Air?

Answer 22

Tissues: 1540 m/s or 1.540 mm/microsecond

Air = 330 m/s

Question 23

Equation for depth
Equation for PRF?
Equation for Nyquist limit?

Answer 23

Depth = (time/2)(c)

PRF = 1/PRP

NL = 1/2 PRF