Carbon dioxide-oxygen relationships in gas exchange of animals. In memory of Hermann Rahn

In external gas exchange of vertebrates, behavior of the respiratory gases CO2 and O2 can in many cases adequately be explained by the different physico-chemical properties of the gases, including solubility, chemical combination in blood and tissue, and diffusivity. In particular, the differences in behavior between CO2 and O2 are often of particular relevance. This is demonstrated on a number of examples of gas exchange mechanisms in vertebrates, including (1) exchange ratio after changes in ventilation, (2) local variations of pulmonary ventilation/perfusion ratio, (3) absorption of gas from gas pockets, (4) water vs. air breathing, (5) multimodal breathing, (6) skin breathing, (7) gas exchange of avian eggs, (8) anomalous gas/blood CO2 equilibration, (9) blood/gas CO2 equilibration in avian lungs, (10) pulmonary diffusing capacity, (11) blood/water CO2 equilibration in fish gills, (12) deposition of gas into fish swim bladder.