The presence of air in the body's tissues. Divided into two types, surgical and pulmonary emphysema, the former occurs when air escapes from leaks in the LUNGS and OESOPHAGUS – perhaps as the result of injury or infection – and collects in the tissues of the chest and neck. Air occasionally escapes into other tissues as a result of surgery or injury, and bacterial infection can also produce gas in soft tissues (see gas gangrene under GANGRENE). Air or gas gives the affected tissue an unmistakable crackling feel when touched, and commonly develops in an individual after blowing up balloons. X-rays of an affected area will usually show the presence of air. Such air is generally absorbed by the body when the leak has been sealed.

The second type of emphysema affects the lung tissue and is called pulmonary emphysema. It is now grouped with other lung disorders such as chronic BRONCHITIS and some types of ASTHMA under the umbrella heading CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) (see under this entry for further information).