The Starling equation
describes capillary filtration
FR = Lp x S [ (Pc – Pi) – s (Pc – Pi) ]
FR   filtration rate
S   capillary surface area
Pc   capillary pressure
Pi   interstitial pressure
s   reflection coefficient
Pc   plasma colloid osmotic pressure
Pi   interstitial colloid osmotic pressure
alveolus
Pi
Pi
Pc
Pc