Assessment of long-term bronchiolar clearance of particles from measurements of lung retention and theoretical estimates of regional deposition

Rolf Falk, Klas Philipson, Magnus Svartengren, Ralf Bergmann, Werner Hofmann, Naomi Jarvis, Michael Bailey, Per Camner*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    29 Citations (Scopus)

    Abstract

    Twelve healthy nonsmokers inhaled monodisperse Teflon particles labelled with 51Cr (half-life 27.8 days) with an aerodynamic diameter (d(ae)) of 6.1 μm, 5 at a normal flow, 0.5 L/s, and 7 at an extremely slow flow, 0.05 L/s. Lung retention after 24 hours was measured for about 6 months and could be well described by a 2-component exponential function. After the normal inhalation, 14% of the particles retained after 24 hours cleared with a half- time of 3.7 days and 86% with a half-time of 217 days. After the slow inhalation, 35% of the particles retained after 24 hours cleared with a half- time of 3.6 days and 65% with a half-time of 170 days. Deposition was calculated using 3 different models including the recent Human Respiratory Tract Model (HRTM), adopted by the International Commission on Radiological Protection (ICRP), and a model based on Monte Carlo particle transport, together with an asymmetric lung model. Generally, the 3 models agreed fairly well and predicted a considerably higher deposition in the bronchiolar region (generations 9-15) at the slow flow than at the normal flow. Together, the experimental data and the predictions of the deposition models indicate that about 40% of the particles deposited in the conducting airways during the slow inhalation were retained after 24 hours. They also strongly indicate that the particles which cleared with a half-time of about 4 days were mainly deposited in the bronchiolar region, and that about 25% of the particles deposited in the bronchiolar region cleared in this phase. The experimental data agreed quite well with the HRTM predictions made using its default parameter values for slow clearance in the bronchial tree.

    Original languageEnglish
    Pages (from-to)495-516
    Number of pages22
    JournalExperimental Lung Research
    Volume25
    Issue number6
    DOIs
    Publication statusPublished - 1999

    Bibliographical note

    Funding Information:
    Received 3 August 1998 ; accepted 28 J anuary 1999. We are grateful for skilful technical assistance from M s Ulla Bergsten, M r Lars Persson, and M s IngerOÈ stergren.ThisstudywassupportedbygrantsfromtheSwedishRadiationProtectionInstitute ( SSI ) , the European Commission ( contract no. F14PCT 950026) , the Swedish Heart and Lung Foundation, and the Research Funds of Karolinska I nstitute. Address correspondence to Dr. Per Camner, Division of Inhalation Toxicology, Institute of Environmental Medicine, Karolinska Institute, Box 210, S-171 77 Stockholm, Sweden.

    Keywords

    • Bronchioles
    • Lung retention mucociliary clearance
    • Particle deposition

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