Abstract
The respiratory tract deposition of nonhygroscopic polystyrene monodisperse aerosols is examined in human subjects. Three kinds of polystyrene particles, diameters of 0.188μ, 0.557μ, and 1.305μ (S.D.: 0.0076μ, 0.0108μ, 0.0158μ respectively) produced by Dow Chemical Co. are used to make monodisperse aerosols for inhalation. The aerosols are generated from the particles suspended in water by a nebulizer (Vaponefrin) under a pressure of 20p.s.i. and are stocked in a 9 litter Benedict-Roth type spirometer to dry and to be inhaled. Subjects are 7 healthy males and 1 healthy female (22∼29 years of age) and they are asked to breathe the aerosols in sitting posture by the nose at respiratory rates of 10, 15 and 20 per minute through a rubber mask connected to the spirometer which depicted tidal volume and respiratory flow rate simultaneously. One experiment durates 1∼2 minutes and 60 series of the experiments are performed in all. The aerosol concentration is measured by Kimoto light scatter photometer (Sinclair-Phoenix type) placed between the spirometer and the mask. The aerosol concentration depicted on the recorder of photometer during one respiration consists of 2 parts, an ascending inspiratory part and a descending expiratory part. From each part average concentrations are estimated and deposition rate are calculated for one cycle respiration. Though there are ca. 15 respiration cycle in one experiment, first 3 of them being excluded to avoid the influence of residual volume, 10 cycles are taken to get an average deposition rate for one experiment. The deposition rate is examined in relation to respiratory rate, tidal volume and respiratory flow rate.
Aerosol depositions in the respiratory tract vary subject to subject, however, the larger the particle size, the higher the percent of deposition. The aerosols of diameters 0.188μ and 0.557μ showed considerably same and low deposition rates in all the respiratory rates used, which suggests the minimum deposition size will exist in the vicinity of these sizes.
The respiratory rate is the next largest variable affecting deposition, that is, the less the respiratory rate the more the deposition, which is most eminently seen in 1.305μ particles. The tidal volume and the flow rate have no relation to the deposition rate.
