Equations Flashcards
Darcy’s law of flow
flow = Pressure/ Resistance
Cardiac output
CO= BP/ VR CO= SV x HR CO = (ABP- RAP)/ TPR
Poiseuille’s law
Resistance = (8 x length x viscosity) / radius^4
Venous return
VR = (MSFP-RAP)/ RvR
Fick’s law
Flow = SA of capillary x permeability of solute ([concentration in capillary- conc in If])
Starling’s equation
Volume flow = hydraulic permeability {K} ((P in capillary- P in If)- colloid reflection coefficient (oncotic pressure of Capillary- oncotic p of If)
Diffusion equation
Time = k x distance squared
Net flux
Net flux = (change in concentration) x (area/thickness) x Diffusion coefficient
Perfect gas equation
PV= nRT
Constant pressure etc
P1 x (V1/T1) = P2 x (v2/T2)
Partial pressure
Partial pressure = fraction of mixture occupied by gas x total pressure extorted by mix
Expired minute volume
VE = tidal volume x breathing frequency
Alveolar ventilation
Alveolar ventilation= (tidal vol- dead space vol) x frequency
Vol of expired CO2 per minute
Vol of expired CO2 per minute= alveolar ventilation x fractional conc of CO2 in alveolar gas)
Alveolar ventilation in BTPS
Alveolar vent = (VECO2/ PACO2) x K {mmHg x l/ml}
Alveolar gas equation
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]
Transmural pressure
Pressure inside- pressure outside
Specific compliance
Compliance/ FRC
La place’s law
P= (2 x surface tension)/ radius
Henry’s law
Conc= partial pressure x solubility
Diffusion coefficient
D = solubility / square root of molecular weight
Oxygen conc of blood
[Blood O2] = (1.39x [Hb] x % saturation) + (0.003 x PO2)
Henderson hasselbach
pH = pKa + log(HCO3-/CO2)
As obeys Henry law, CO2 replaced by 0.03 PCO2
Van’t hoff equation
Osmotic pressure x volume = nRT
Osmolality
Amount of solute/ amount of solvent
GFR
GFR= starlings law equation
Renal blood flow
RBF= Pressure grad / (Reff + Raff)
Filtration fraction
filtration fraction = GFR/ renal plasma flow
Clearance
Clearance= rate of excretion/ plasma conc
Clearance ratio
Clearance ratio = clearance of X/ clearance of insulin
PKA of blood plasma
6.1
potential divider internal resistance
Ri = external resistance [(total voltage- voltage across resistor)/ voltage across resistor]
