Design of the mammalian respiratory system. I. Problem and strategy.

This paper introduces a series of reports on the structure and function of the respiratory system of mammals. We propose and justify the hypothesis that structural design is a limiting factor for O2 flow at each level of the respiratory system. The background, the reasons, and the plan for the studies are described. The main approach is to compare the size of respiratory structures with maximal O2 consumption in a series of mammals spanning several orders of magnitude in body size. The papers that follow present the methods and results for maximal O2 consumption, pulmonary diffusing capacity, mitochondrial volume, and capillary density in muscles.