When capillary and interstitial hydrostatic pressures are 30 mm Hg and 10 mm Hg, respectively, and colloid oncotic pressure in capillaries and in interstitium are 22 mm Hg and 5 mm Hg, respectively, how much is the net filtration pressure?

Forces oring filtration out of the capillaries ~ (1) Capillary hydrostatic pressure (30 mm Hg) (2) Interstitial fluid colloid oncotic pressure (5 mm Hg). Thus, total force that ors filtration = 30 + 5 = 35 mm Hg. Forces that pull the fluid back into the capillaries ~ (1) Plasma colloid oncotic pressure (22 mm Hg) (2) Interstitial fluid hydrostatic pressure (10 mm Hg). Thus, total force that opposes filtration = 22 + 10 = 32 mm Hg. Hence, net filtration pressure = 35 - 33 = + 3 mm Hg.