title: Regional deposition and retention of particles in shallow, inhaled boluses: effect of lung volume.
abstract: The regional deposition of particles in boluses delivered to shallow lung depths and their subsequent retention in the airways may depend on the lung volume at which the boluses are delivered. To evaluate the effect of end-inspiratory lung volume on aerosol bolus delivery, we had healthy subjects inhale radiolabeled, monodisperse aerosol (99mTc-iron oxide, 3.5-microm mass median aerodynamic diameter) boluses (40 ml) to a volumetric front depth of 70 ml into the lung at lung volumes of 50, 70, and 85% of total lung capacity (TLC) end inhalation. By gamma camera analysis, we found significantly greater deposition in the left (L) vs. right (R) lungs at the 70 and 85% TLC end inhalation; ratio of deposition in L to R lung, normalized to L-to-R ratio of lung volume (mean L/R), was 1.60 +/- 0.45 (SD) and 1. 96 +/- 0.72, respectively (P < 0.001 for comparison to 1.0) for posterior images. However, at 50% TLC, L/R was 1.23 +/- 0.37, not significantly different from 1.0. These data suggest that the L and R lungs may be expanding nonuniformly at higher lung volumes. On the other hand, subsequent retention of deposited particles at 2 and 24 h postdeposition was independent of L/R at the various lung volumes. Thus asymmetric bolus ventilation for these very shallow boluses does not lead to significant increases in peripheral alveolar deposition. These data may prove useful for 1) designing aerosol delivery techniques to target bronchial airways and 2) understanding airway retention of inhaled particles.
authors.affiliation: Center for Environmental Medicine and Lung Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: W D
authors.initials: WD
authors.lastname: Bennett
authors.forename: G
authors.initials: G
authors.lastname: Scheuch
authors.forename: K L
authors.initials: KL
authors.lastname: Zeman
authors.forename: J S
authors.initials: JS
authors.lastname: Brown
authors.forename: C
authors.initials: C
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Heyder
authors.forename: W
authors.initials: W
authors.lastname: Stahlhofen
mesh_terms: D000328:Adult; D000336:Aerosols; D005290:Ferric Compounds / Q000493:pharmacokinetics; D006801:Humans; D008168:Lung / Q000033:anatomy & histology* / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015656:Respiratory Mechanics / Q000502:physiology*; D017556:Technetium Compounds / Q000493:pharmacokinetics; D014109:Total Lung Capacity / Q000502:physiology; D014980:Xenon Radioisotopes / Q000493:pharmacokinetics
chemical_list: D000336:Aerosols; D005290:Ferric Compounds; D019275:Radiopharmaceuticals; D017556:Technetium Compounds; D014980:Xenon Radioisotopes; C046128:technetium Tc 99m ferric oxide