Effect of microgravity and hypergravity on deposition of 0.5- to 3-micron-diameter aerosol in the human lung.
We measured intrapulmonary deposition of 0. 5-, 1-, 2-, and 3-micron-diameter particles in four subjects on the ground (1 G) and during parabolic flights both in microgravity (microG) and at approximately 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 approximately 1.6 G, deposition increased with increasing particle size. In microG, 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-micron-diameter particles, whereas for 0.5- and 1.0-micron-diameter particles, deposition increased less between microG and 1 G than between 1 G and approximately 1.6 G. Comparison with numerical predictions showed good agreement for 1-, 2-, and 3-micron-diameter particles at 1 and approximately 1.6 G, whereas the model consistently underestimated deposition in microG. The higher deposition observed in microG compared with model predictions might be explained by a larger deposition by diffusion because of a higher alveolar concentration of aerosol in microG and to the nonreversibility of the flow, causing additional mixing of the aerosols.
Darquenne
C
C
Department of Medicine, University of California, San Diego, La Jolla, California 92093-0931, USA. cdarquenne@ucsd.edu
Paiva
M
M
West
J B
JB
Prisk
G K
GK
D000328:Adult; D000336:Aerosols; D004058:Diffusion; D005260:Female; D006801:Humans; D018471:Hypergravity / Q000009:adverse effects*; D008168:Lung / Q000502:physiology*; D008297:Male; D008863:Microspheres; D008875:Middle Aged; D008954:Models, Biological; D010316:Particle Size; D014893:Weightlessness / Q000009:adverse effects*
D000336:Aerosols