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Increase in relative deposition of fine particles in the rat lung periphery in the absence of gravity

Abstract : While it is well recognizedthat pulmonary deposition of inhaled particles is lowered in microgravity(G) compared with gravity on the ground (1G), theabsence of sedimentation causes fine particles to penetrate deeperin the lung in G. Using quantitative magnetic resonance imaging(MRI), we determined the effect of gravity on peripheral deposition(DEPperipheral) of fine particles. Aerosolized 0.95-m-diameter ferricoxide particles were delivered to spontaneously breathing rats placedin plethysmographic chambers both in G aboard the NASA MicrogravityResearch Aircraft and at 1G. Following exposure, lungs wereperfusion fixed, fluid filled, and imaged in a 3T MR scanner. The MRsignal decay rate, R2*, was measured in each voxel of the left lungfrom which particle deposition (DEP) was determined based on acalibration curve. Regional deposition was assessed by comparingDEP between the outer (DEPperipheral) and inner (DEPcentral) areas oneach slice, and expressed as the central-to-peripheral ratio. Total lungdeposition tended to be lower in G compared with 1G (1.01 0.52vs. 1.43 0.52 g/ml, P 0.1). In G, DEPperipheral was larger thanDEPcentral (P 0.03), while, in 1G, DEPperipheral was not significantlydifferent from DEPcentral. Finally, central-to-peripheral ratio was significantlyless in G than in 1G (P 0.05). These data show a largerfraction of fine particles depositing peripherally in G than in 1G,likely beyond the large- and medium-sized airways. Although notmeasured, the difference in the spatial distribution of depositedparticles between G and 1G could also affect particle retention rates,with an increase in retention for particles deposited more peripherally.
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Contributor : Jessica Oakes <>
Submitted on : Tuesday, December 16, 2014 - 3:26:01 AM
Last modification on : Wednesday, August 7, 2019 - 12:18:06 PM

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Chantal Darquenne, Maria G. Borja, Jessica Oakes, Ellen C. Breen, Mark Olfert, et al.. Increase in relative deposition of fine particles in the rat lung periphery in the absence of gravity. Journal of Applied Physiology, American Physiological Society, 2014, 117, pp.880-886. ⟨10.1152/japplphysiol.00298.2014⟩. ⟨hal-01095644⟩



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