Deposition and clearance: unique problems in the proximal airways and oralcavity in the young and elderly

Prospective longitudinal studies measuring aerosol behavior in the respirat ory tract as humans age have not been performed. The present paper reviews observations related to aging of the respiratory tract and other effects mo re likely due primarily to disease and iatrogenic causes. Upper airway depo sition was found to approximate 50% in children during inhalation of drugs thought to be designed primarily for deposition in the lower respiratory tr act. In older subjects, aging per se did not have a major impact on the dep osition of aerosols. Disease processes that develop with age were shown to be the primary cause of deposition abnormalities. Flow-limitation in centra l airways was proposed as a major factor responsible for central airway dep osition as well as abnormal clearance in common obstructive lung diseases. The oral cavity, a source of pathogenic organisms causing pneumonia, was al so studied in the elderly. Salivary clearance, often abnormal in the aged, was related to colonization with pathogenic bacteria. Salivary clearance wa s not obviously reduced by aging per se but by iatrogenic sources such as d rug therapy for other diseases. (C) 2001 Elsevier Science B.V. All rights r eserved.