Pulmonary edema due to increased microvascular permeability to fluid and protein.

where Qf is the net transvascular fluid flow, K is the fluid filtration coefficient, P is the hydrostatic pressure in the microvascular* lumen (mv) and perimicrovascular* interstitial fluid (pmv), respectively; a is a weighted plasma protein reflection coefficient which determines the "effective" transvascular protein osmotic pressure difference; and II is the protein osmotic pressure in the plasma (mv) and perimicrovascular (pmv) compartments, respectively. According to Equation 1, the two major types of edema are that due to increased driving pressure (high pressure edema) and that due to altered integrity of the microvascular membrane (permeability edema). High pressure edema may be of cardiac origin (increased microvascular hydrostatic pressure due to left atrial hypertension), but it also may occur when cardiac function is normal as in overexpansion of extracellular volume by crystalloid fluid infusions' (increased pulmo-