An indication on the biological variability of aerosol total deposition in humans

Abstract

A technique for the assessment of the total deposition efficiency, DE, in the human respiratory tract is described. It is based on the use of non-wettable solid spherical monodisperse particles in the 0.3 to 1.5 µm range and on the measurement of particle concentrations in the inhaled and exhaled air. The results of total deposition measurements as a function of particle size taken on 6 volunteers are presented. A wide variability has been found among the subjects; it is discussed and, in contrast with some literature data, there is no apparent correlation with normal expiratory reserve volumes, ERV_N. Therefore at 0.6 µm the deposition has been measured at various ERV. The scatter of data is considerable, but it can be greatly reduced if the relative deposition (ratio of the effective DE to DE_N, the deposition at “normal” volumes) is expressed as a function of the relative ERV, (the ratio of the effective ERV to the normal ERV_N). Measurements have been performed with monodisperse and unipolarly charged particles on two subjects characterized by different DE_N and ERV_N. The contribution of electrostatic effects to deposition was not distinguishable in the two subjects.