A model of the factors affecting interstitial volume in oedema. Part I: Hierarchies, some new factors and their equations.

: A mathematical model has been constructed to investigate the alterations, in amount and in importance, of the Factors controlling interstitial fluid volume in a number of steady-state oedemas. There are many so-called "Safety Factors" (at least 15), including a whole group concerned with regulating the amount of protein in the tissues (and thus tissue colloidal osmotic pressure). They are often in long hierarchies (of even up to 11 Factors), each influencing the next. Sometimes a Factor is recursive, i.e., it influences itself (either positively or negatively) via a Hierarchy of other Factors. The effects of some Factors differ in different Hierarchies, i.e., an increase in the Factor will increase VI via some of the Hierarchies and decrease it via some other Hierarchies. Which effect is most important varies with the Hierarchies and conditions existing at the time. The Factors are best compared if expressed in the same units: ml/min/100g of tissue. This is possible via appropriate multiplication factors derived from the relevant equations.