Emphysema

**Definition:** Emphysema is defined by abnormal and permanent enlargement of the airspaces that are distal to the terminal bronchioles. This is accompanied by destruction of the airspace walls, without obvious fibrosis (i.e. there is no fibrosis visible to the naked eye). Emphysema can exist in individuals who do not have airflow obstruction; however, it is more common among patients who have moderate or severe airflow obstruction.

**Exclusions:** - Compensatory emphysema - emphysema due to inhalation of chemicals, gases, fumes or vapours - Interstitial emphysema originating in the perinatal period - emphysema mediastinal - emphysema, surgical (subcutaneous) - Traumatic subcutaneous emphysema, not elsewhere classified - emphysema with chronic (obstructive) bronchitis - emphysematous (obstructive) bronchitis