Physiologic stability and physiologic state.

Several disease states (e.g., disseminated inflammation) demonstrate physiologic stability: they resolve only slowly and are resistant to both specific and symptomatic therapies. The existence of multiple stable physiologic states, including both health and disease states, is not anticipated by classical, linear descriptions of physiologic control mechanisms. Multiple stable states are, however, predicted by a simple nonlinear model in which the resistance to perturbation derives from interconnections among the model's elements. If the stability of selected disease states derives from nonlinear interactions among cells, tissues, and organs, then some therapies aimed at supporting or normalizing performance of specific organs may be misdirected.