Physiology equations

Question 1

What is the Bohr equation?

Answer 1

Dead space

Vd/Vt = (PaCO2 - PeCO2) / PaCO2

Question 2

What is the Ficks equation for flow?

Answer 2

Flow = (delta P x A x diffusion coefficient) / thickness

Diffusion coefficient = solubility / square root of molecular weight

Question 3

What are the equation for SV and ejection fraction?

Answer 3

SV = EDV - ESV

Ejection fraction = (SV/EDV) x 100

Question 4

What are the equations for SVR and PVR?

Answer 4

SVR = (MAP - CVP) / CO

PVR = (Mpasp - PCWP) / CO

Both x 80

PCWP = LA pressure

Question 5

How do we calculate VO2 max and how do we rearrange this to calculate CO?

Answer 5

VO2 = CO x (CaO2 - CvO2)

CO = VO2 / (CaO2 - CVO2)

Question 6

How do we calculate oxygen content of blood and O2 delivery?
And extraction?

What are normal values?

Answer 6

Content = (Hb x 1.34 x sats) + (0.225 x PaO2)

Delivery = CO x CaO2

Extraction = VO2/DO2

Normal arterial O2 = 13.3 and 20ml
Venous = 5.3 and 15ml pre Dl

Question 7

What is the alveolar gas equation?

Answer 7

FiO2 x (101 - 6.3) - PaCO2/R

R = VCO2/CO2

Question 8

What is the shunt equation?

Answer 8

Qs/Qt = (CCO2 - CaO2)/ (CCO2 - CVO2)

Question 9

What is the equation for osmotic pressure and what is its symbol?

Answer 9

Symbol = Pi

Pi = RTC
C = osmolarity

Question 10

What is the startling equation?

Answer 10

(Arterial hydrostatic - venous end hydrostatic) - (venous osmotic - arterial osmotic)

Question 11

What is the Nernst equation?

Answer 11

(RT)/FZ x loge (sodium inside/sodium outside)

F = faraday constant and Z = valency of Na

Question 12

What are the laplace equations for the heart and alveoli?

Answer 12

Heart = 2th/r

Alveoli = 2t/r