Safety Factors in the Design of Gas Exchangers

Abstract

The extent to which natural selection has produced concordance between the functional capacities of structural systems and their demands was termed ‘symmorphosis’ by Taylor and Weibel (1981). The concept has become a highly debatable and controversial subject in morphology, physiology and evolutionary biology (e.g. Weibel et al. 1991). As regards O₂ delivery systems (e.g. Weibel et al. 1991; Maina 1998b), it has been found that symmorphosis is tenable only as far as the system’s components are quantitatively proportional to the maximal organismal functional requirements and loading. Since gas exchangers must meet the metabolic needs for O₂ by the body under shifting conditions, that is, rest to exercise, under thermal stress or under hypoxia, they must be structurally and functionally tractable. Highly trained human athletes and some elite animals such as the horse, the dog, the pronghorn antelope, Antilocapra americana, and the cheetah, Acionyx jubatus, can increase their O₂ consumption above rest by factors 20–30 times (e.g. Lindstedt et al. 1991).

Three guidelines of modern architecture are equally valid for biological forms: a building should be the realisation of clear, elegant structural ideas; it should be solid and economic; and it should be aesthetically harmonious with the environment. Tributsch (1984)