Application of aerosols

Abstract

Inhalation is a very efficient pathway to bring airborne material into the human body. For aerosols it is almost the only way to interact with the biological system. Aerosols are liquid or solid particles suspended in air. They are applied for local lung therapy as well as for systemic therapy. Furthermore, they serve as a diagnostic tool for the study of lung morphometry, lung physiology and clearance mechanism. Frequently, experimental animals such as rodents and dogs are used to investigate pulmonary effects of inhaled aerosols, particularly in view of particle related toxic effects. Particles as they are inhaled will be transported through the respiratory system and will be deposited in various regions in the lung depending on the particle size, the breathing pattern and the lung morphology, i.e. species. The applied dose is determined by the (mass) concentration and the size distribution of the inhaled aerosol and the regional deposition efficiency which is a function of particle size. The respiratory system can be divided into three compartments: the extrathoracic region (nose, mouth cavity, pharynx, larynx), the tracheo-bronchial airways and the alveolar airspace. In order to maximize the expected effect of the aerosol and to minimize side-effects it is often required to deliver the particles only to one specific region of the lung. For example, substances designed to get into the systemic circulation should be preferentially deposited in the alveolar space whereas bronchio dilatators act locally in the bronchial region and, thus, should be deposited preferentially in this region.