title: Regional Ventilation Is the Main Determinant of Alveolar Deposition of Coarse Particles in the Supine Healthy Human Lung During Tidal Breathing.
abstract: BACKGROUND
  To quantify the relationship between regional lung ventilation and coarse aerosol deposition in the supine healthy human lung, we used oxygen-enhanced magnetic resonance imaging and planar gamma scintigraphy in seven subjects.
  
  
  METHODS
  Regional ventilation was measured in the supine posture in a 15 mm sagittal slice of the right lung. Deposition was measured by using planar gamma scintigraphy (coronal scans, 40 cm FOV) immediately postdeposition, 1 hour 30 minutes and 22 hours after deposition of99mTc-labeled particles (4.9 μm MMAD, GSD 2.5), inhaled in the supine posture (flow 0.5 L/s, 15 breaths/min). The distribution of retained particles at different times was used to infer deposition in different airway regions, with 22 hours representing alveolar deposition. The fraction of total slice ventilation per quartile of lung height from the lung apex to the dome of the diaphragm at functional residual capacity was computed, and co-registered with deposition data-apices aligned-using a transmission scan as reference. The ratio of fractional alveolar deposition to fractional ventilation of each quartile (r) was used to evaluate ventilation and deposition matching (r > 1, regional aerosol deposition fraction larger than regional ventilation fraction).
  
  
  RESULTS
  r was not significantly different from 1 for all regions (1.04 ± 0.25, 1.08 ± 0.22, 1.03 ± 0.17, 0.92 ± 0.13, apex to diaphragm, p > 0.40) at the alveolar level (r22h). For retention times r0hand r1h30, only the diaphragmatic region at r1h30differed significantly from 1.
  
  
  CONCLUSIONS
  These results support the hypothesis that alveolar deposition is directly proportional to ventilation for ∼5 μm particles that are inhaled in the supine posture and are consistent with previous simulation predictions that show that convective flow is the main determinant of aerosol transport to the lung periphery.
authors.affiliation: 1 Pulmonary Imaging Laboratory, Department of Medicine, University of California , San Diego, La Jolla, California.
authors.forename: Rui Carlos
authors.initials: RC
authors.lastname: Sá
authors.affiliation: 2 Department of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina.
authors.forename: Kirby L
authors.initials: KL
authors.lastname: Zeman
authors.affiliation: 2 Department of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina.
authors.forename: William D
authors.initials: WD
authors.lastname: Bennett
authors.affiliation: 1 Pulmonary Imaging Laboratory, Department of Medicine, University of California , San Diego, La Jolla, California.|3 Pulmonary Imaging Laboratory, Department of Radiology, University of California , San Diego, La Jolla, California.
authors.forename: G Kim
authors.initials: GK
authors.lastname: Prisk
authors.affiliation: 1 Pulmonary Imaging Laboratory, Department of Medicine, University of California , San Diego, La Jolla, California.
authors.forename: Chantal
authors.initials: C
authors.lastname: Darquenne
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000336:Aerosols; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000378:metabolism*; D012123:Pulmonary Ventilation / Q000502:physiology*; D011877:Radionuclide Imaging / Q000379:methods; D012119:Respiration; D016683:Supine Position; D013671:Technetium Tc 99m Sulfur Colloid / Q000008:administration & dosage* / Q000493:pharmacokinetics; D013990:Tidal Volume; D013997:Time Factors
chemical_list: D000336:Aerosols; D013671:Technetium Tc 99m Sulfur Colloid
keywords: coarse aerosol deposition; human lung; multimodal imaging; ventilation