Equations

Question 1

Darcy’s law of flow

Answer 1

flow = Pressure/ Resistance

Question 2

Cardiac output

Answer 2

CO= BP/ VR
CO= SV x HR
CO = (ABP- RAP)/ TPR

Question 3

Poiseuille’s law

Answer 3

Resistance = (8 x length x viscosity) / radius^4

Question 4

Venous return

Answer 4

VR = (MSFP-RAP)/ RvR

Question 5

Fick’s law

Answer 5

Flow = SA of capillary x permeability of solute ([concentration in capillary- conc in If])

Question 6

Starling’s equation

Answer 6

Volume flow = hydraulic permeability {K} ((P in capillary- P in If)- colloid reflection coefficient (oncotic pressure of Capillary- oncotic p of If)

Question 7

Diffusion equation

Answer 7

Time = k x distance squared

Question 8

Net flux

Answer 8

Net flux = (change in concentration) x (area/thickness) x Diffusion coefficient

Question 9

Perfect gas equation

Answer 9

PV= nRT

Question 10

Constant pressure etc

Answer 10

P1 x (V1/T1) = P2 x (v2/T2)

Question 11

Partial pressure

Answer 11

Partial pressure = fraction of mixture occupied by gas x total pressure extorted by mix

Question 12

Expired minute volume

Answer 12

VE = tidal volume x breathing frequency

Question 13

Alveolar ventilation

Answer 13

Alveolar ventilation= (tidal vol- dead space vol) x frequency

Question 14

Vol of expired CO2 per minute

Answer 14

Vol of expired CO2 per minute= alveolar ventilation x fractional conc of CO2 in alveolar gas)

Question 15

Alveolar ventilation in BTPS

Answer 15

Alveolar vent = (VECO2/ PACO2) x K {mmHg x l/ml}

Question 16

Alveolar gas equation

Answer 16

Partial P of O2 in alveolar gas = PP of O2 inspired - PP of CO2 in alveoli [frac conc of O2 in inspired air + (1- FIO2)/ Resp exchange ratio]

Question 17

Transmural pressure

Answer 17

Pressure inside- pressure outside

Question 18

Specific compliance

Answer 18

Compliance/ FRC

Question 19

La place’s law

Answer 19

P= (2 x surface tension)/ radius

Question 20

Henry’s law

Answer 20

Conc= partial pressure x solubility

Question 21

Diffusion coefficient

Answer 21

D = solubility / square root of molecular weight

Question 22

Oxygen conc of blood

Answer 22

[Blood O2] = (1.39x [Hb] x % saturation) + (0.003 x PO2)

Question 23

Henderson hasselbach

Answer 23

pH = pKa + log(HCO3-/CO2)

As obeys Henry law, CO2 replaced by 0.03 PCO2

Question 24

Van’t hoff equation

Answer 24

Osmotic pressure x volume = nRT

Question 25

Osmolality

Answer 25

Amount of solute/ amount of solvent

Question 26

GFR

Answer 26

GFR= starlings law equation

Question 27

Renal blood flow

Answer 27

RBF= Pressure grad / (Reff + Raff)

Question 28

Filtration fraction

Answer 28

filtration fraction = GFR/ renal plasma flow

Question 29

Clearance

Answer 29

Clearance= rate of excretion/ plasma conc

Question 30

Clearance ratio

Answer 30

Clearance ratio = clearance of X/ clearance of insulin

Question 31

PKA of blood plasma

Answer 31

6.1

Question 32

potential divider internal resistance

Answer 32

Ri = external resistance [(total voltage- voltage across resistor)/ voltage across resistor]