Effect of microgravity and hypergravity on deposition of 0.5- to 3-μm-diameter aerosol in the human lung

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Abstract
Darquenne, Chantal, Manuel Paiva, John B. West, and G. Kim Prisk. Effect of microgravity and hypergravity on deposition of 0.5- to 3-μm-diameter aerosol in the human lung. J. Appl. Physiol. 83(6): 2029–2036, 1997.—We measured intrapulmonary deposition of 0.5-, 1-, 2-, and 3-μm-diameter particles in four subjects on the ground (1 G) and during parabolic flights both in microgravity (μG) and at ∼1.6 G. Subjects breathed aerosols at a constant flow rate (0.4 l/s) and tidal volume (0.75 liter). At 1 G and ∼1.6 G, deposition increased with increasing particle size. In μG, differences in deposition as a function of particle size were almost abolished. Deposition was a nearly linear function of the G level for 2- and 3-μm-diameter particles, whereas for 0.5- and 1.0-μm-diameter particles, deposition increased less between μG and 1 G than between 1 G and ∼1.6 G. Comparison with numerical predictions showed good agreement for 1-, 2-, and 3-μm-diameter particles at 1 and ∼1.6 G, whereas the model consistently underestimated deposition in μG. The higher deposition observed in μG compared with model predictions might be explained by a larger deposition by diffusion because of a higher alveolar concentration of aerosol in μG and to the nonreversibility of the flow, causing additional mixing of the aerosols.