  In this work we present a mathematical framework that quantifies the
gas-exchange processes in the lung. The theory is based on the solution of the
one-dimensional diffusion equation on a simplified model of lung septum. Gases
dissolved into different compartments of the lung are all treated separately
with physiologically important parameters. The model can be applied in magnetic
resonance of hyperpolarized xenon for quantification of lung parameters such as
surface-to-volume ratio and the air-blood barrier thickness. In general this
model provides a description of a broad range of biological exchange processes
that are driven by diffusion.
