concept

Unidirectional airflow

A breathing pattern in which air flows one direction through the lung instead of in and out the same door. The exchange surface is always bathed in fresh air, the pressure slope held permanently open - which is why a bar-headed goose can cross the Himalaya through air thin enough to drop a running mammal. Once thought a bird's invention, it also turns up in alligators, monitor lizards, and iguanas - an ancient answer evolution keeps re-deriving. It is almost certainly how Pandora's flyers breathe.