Dispersion of 0,5- to 2-µm aerosol in µG and hypergravity as a probe of convective inhomogeneities in the lung

Dispersion of 0.5- to 2-µm aerosol in µG and hypergravity as a probe of convective inhomogeneity in the lung. J. Appl. Physiol. 86(4): 1402–1409, 1999.—We used aerosol boluses to study convective gas mixing in the lung of four healthy subjects on the ground (1 G) and during short periods of microgravity (µG) and hypergravity (,1.6 G). Boluses of 0.5-, 1-, and 2-µm-diameter particles were inhaled at different points in an inspiration from residual volume to 1 liter above functional residual capacity. The volume of air inhaled after the bolus [the penetration volume (Vp)] ranged from 150 to 1,500 ml. Aerosol concentration and flow rate were continu-ously measured at the mouth. The dispersion, deposition, and position of the bolus in the expired gas were calculated from these data. For each particle size, both bolus dispersion and deposition increased with Vp and were gravity dependent