Starling forces describe the movement of fluids between the vasculature and interstitial spaces. Fluid movement is determined by the balance of hydrostatic and osmotic pressure gradients 1.
Net pressure = [ (Pc - Pi) - (pc - pi) ]
- Pc = hydrostatic pressure of the capillary
- Pi = hydrostatic pressure of the interstitium
- pc = osmotic pressure of the capillary
- pi = oncotic pressure of the interstitium
The balance between these forces determines the net pressure which dictates the direction of fluid movement 1.