Air trapping, also called gas trapping, is an abnormal retention of air in the lungs where it is difficult to exhale completely.[1] It is observed in obstructive lung diseases such as asthma, bronchiolitis obliterans syndrome and chronic obstructive pulmonary diseases such as emphysema and chronic bronchitis.
Air trapping is not a diagnosis but is a presentation of an illness, and can be a guide to the appropriate differential diagnosis.