| The total deposition of monodisperse, sodium chloride aerosol particles 0.026 to 0.19 (mu)m in diameter was measured in the respiratory tracts of five, healthy human subjects. Deposition was measured by comparing the aerosol content in inhaled and exhaled air. The inhalation system consisted of: an electrostatic aerosol classifier that produced the aerosols, a fast-switching solenoid valve system that separated inhaled from exhaled air, an aerosol electrometer that measured aerosol concentrations, and an inductive plethysmograph that measured tidal volumes and was part of a visual feedback system that assisted the subjects in following standardized breathing patterns. All breaths were taken through the mouth, initiated from functional residual capacity, and had equal inhaled and exhaled tidal volumes and flowrates with no pauses.; For a tidal volume of 1000 cm('3) and a flowrate of 500 cm('3)/s, the deposition measurements were (mean +/- S.D.): 37.2 +/- 8.4% for 0.026 (mu)m, 23.8 +/- 3.3% for 0.051 (mu)m, 22.8 +/- 3.1% for 0.096 (mu)m, and 31.8 +/- 6.2% for 0.19 (mu)m aerosols, all in terms of the dry volume equivalent diameter. The deposition minimum corresponded to a particle size of 0.08 (mu)m. The mean coefficient of variation of the subject's deposition measurements was 17.4 +/- 4.4%. Deposition did not significantly correlate with measures of lung volume or body size. When the sizes of the hygroscopic particles were increased by factors of 3.5 to 5.5, corresponding to sizes they would grow to if the air in the respiratory tract had a relative humidity of 99.5%, the resultant deposition curve paralleled deposition curves reported for insoluble aerosols.; Lengthening the breathing period (time of the breathing cycle) from 4 to 8 seconds per breath while maintaining the flowrate at 500 cm('3)/s increased deposition by an absolute amount of 11.3 +/- 3.1%. Dimensional analysis showed the 0.026 and 0.051 (mu)m aerosols were depositing by diffusion in the lung periphery. The 0.096 and 0.19 (mu)m aerosols were primarily depositing by sedimentation. Increasing the flowrate to 1000 cm('3)/s did not convincingly show any increase in deposition due to impaction. |
