In biology,<unk>  is a measurement of the lung's ability to transfer gases. Oxygen uptake may be limited by<unk>  in circumstances low ambient oxygen or high pulmonary blood flow.  Carbon dioxide is not limited by<unk>  under most circumstances.
The "diffusing<unk> " or<unk> " is part of a comprehensive test series of lung function called pulmonary function testing.  In Europe, this is often called the "transfer factor".
Diffusion capacity
Ventilation/perfusion ratio
Oxygen permeability
Cardiac output
Alveolar-arterial gradient
Stroke volume
Volumetric flow rate
Oxygen Enhancement Ratio