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Determining deposition sites of inhaled lung particles and their effect on clearance.

Langenback EG; Bergofsky EH; Halpern JG; Foster WM
J Appl Physiol 1990 Apr; 68(4):1427-1434
The deposition sites of inhaled particles and their effect on pulmonary clearance were examined in sheep. Mixed breed female sheep inhaled an aerosol consisting of cobalt-57 (Co-57) tagged carbonized polystyrene spheres having a count median diameter of 3.0 microns. The distribution pattern and pulmonary clearance of Co-57 activity was determined by whole body autoradiographic and scintillation techniques for up to 72 hours after exposure. The sheep were reexposed to the aerosol after the Co-57 activity had decreased to below 0.5% of its initial value. The distribution and pulmonary clearance were determined as before. All sheep were then killed and the lungs were removed. The length of the bronchial trees were determined. The number of particles deposited in the bronchi, respiratory bronchioles, and alveoli were determined by scintillation counting and optical microscopy. Approximately 4.8% of the particles were deposited in bronchi having diameters of 1 millimeter (mm) or larger. Approximately 57.3% of the particles were deposited in the alveoli and respiratory bronchioles and 37.9% in bronchi having diameters less than 1mm. Total lung clearance as a percentage of initially deposited particles after 24, 48, and 72 hours was 33.5, 10.9, and 6.1%, respectively. Particles deposited in bronchi having diameters greater than 1mm were cleared within 2 to 4 hours. Most of the particles deposited in the tracheobronchial tree were cleared within 45 hours. Most of the particles deposited in the alveolar regions cleared between 48 and 72 hours. The authors conclude that tracheobronchial clearance of inhaled particles probably involves a delayed transport over distances of 6 to 10mm in bronchi having diameters of less than 1mm and a fast phase through larger bronchi over distances of 32 to 144mm.
NIOSH Publication; NIOSH Grant; In vivo studies; Laboratory animals; Inhalation studies; Particulates; Radiobiology; Pulmonary clearance; Biokinetics
Medicine Suny at Stony Brook Hsc, T-17, Room 040, Stony Brook, NY 11794
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Journal of Applied Physiology
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State University New York Stony Brook, Stony Brook, New York
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