Oedema, Starling and pulse reverse osmosis: towards a possible biochemical marker for oedema

Several conflicting theories have been proposed to explain the development of oedema. Pulse reverse osmosis (PRO) suggests that oedema occurs when the mean pulse capillary pressure exceeds the osmotic gradient between the plasma and the interstitial fluid. In order to test this concept mean arterial blood pressures and colloid osmotic pressures were taken in a group of healthy volunteers, a group of patients with bilateral ankle oedema and a group of treated hypertensives. Patients with oedema were found to have colloid osmotic pressures (COP's) which were significantly less than those of the healthy volunteers (p <0.001) and the treated hypertensives (p <0.001). The results support the oedema mechanism proposed by PRO and indicate that the relationship between blood pressure and COP may be a useful biochemical marker of oedema and its treatment. Further study is required to numerically quantify this relationship.