1) The withdrawal of fluid or gases from the natural cavities of the body or from cavities produced by disease. It may be performed for curative purposes; alternatively, a small amount of fluid may be drawn off for diagnosis of its nature or origin. An instrument called an aspirator is used to remove blood and fluid from a surgical-operation site – for example, the abdomen or the mouth (in dentistry).

PLEURISY with effusion and PERICARDITIS with effusion are conditions in which aspiration is sometimes performed. The spinal canal is aspirated by the operation of LUMBAR PUNCTURE. In children the ventricles of the brain are sometimes similarly relieved from excess of fluid by piercing the fontanelle (soft spot) on the infant's head. (See HYDROCEPHALUS.)

2) Accidental inspiration of stomach contents into the airways, for example in an unconscious patient, which may lead to pneumonia.