Model schematic representing O₂ uptake, transport and consumption.

<p>O₂ stores are represented by the alveolar, arterial, and venous compartments. Two dynamically-independent levels of O₂ uptake are denoted: pulmonary O₂ uptake () and metabolic consumption (). R-L shunt is also included. T_a is the arterial transit time. Symbols are described in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1000588#pcbi-1000588-t001" target="_blank">Table 1</a>.