title: Left-to-right asymmetry of aerosol deposition after shallow bolus inhalation depends on lung ventilation.
abstract: BACKGROUND
  After shallow bolus inhalation of radiolabeled aerosols, gamma camera imaging has shown a left-right asymmetry, with a higher fraction of deposited particles in the left lung. It was not clear, however, whether this phenomenon was an effect of asymmetry in lung ventilation or aerosol deposition efficiency.
  
  
  METHODS
  Lung ventilation and aerosol deposition was studied after shallow bolus inhalation and gamma camera imaging in nine healthy nonsmokers and 10 asymptomatic smokers. A 100-mL (81m)Kr-gas boli were administered within the Fowler and within the phase-1 dead space, respectively. In addition, 1-L full breaths of 81m-Kr-gas were inhaled. For aerosol deposition subjects inhaled 100-mL boli of 100-nm diameter radiolabeled carbon particles with shallow and deep penetration. Left-to-right (L/R) and central-to-peripheral (C/P) activity distribution of the lung was analyzed.
  
  
  RESULTS
  None of the parameters analyzed were significantly different between nonsmokers and smokers. The full-breath 81m-Kr-gas inhalation revealed a similar activity distribution over the left and right lungs, according to their respective volumes (L/R ratio = 0.84 +/- 0.04; mean +/- SE). In contrast, the shallow bolus inhalation of 81m-Kr-gas to the phase-1 dead space revealed more activity in the left lung (L/R ratio = 1.49 +/- 0.15, normalized to full-breath Kr-gas L/R). This same left-right asymmetry was observed for the aerosol after shallow bolus inhalation (L/R ratio = 1.69 +/- 0.15), and there was no significant difference between Kr-gas and aerosol L/R ratio. C/P activity ratios of bolus inhalation to the phase-1 dead space were 1.71 +/- 0.19 and 1.79 +/- 0.15 (normalized to full-breath Kr-gas C/P) for gas and aerosol, respectively, and correlated with the L/R ratios.
  
  
  CONCLUSIONS
  The data show that the asymmetry in shallow aerosol bolus deposition is primarily determined by lung ventilation. The reason for this asymmetry is unclear.
authors: Helmholtz Center Munich, German Research Center for Environmental Health, Clinical Cooperation Group Inflammatory Lung Diseases, Institute for Lung Biology and Disease, and Focus Network Nanoparticles and Health, Gauting and Neuherberg, Germany. moeller@helmholtz-muenchen.de
authors: Winfried
authors: W
authors: Möller
authors: Gabriele
authors: G
authors: Meyer
authors: Gerhard
authors: G
authors: Scheuch
authors: Wolfgang G
authors: WG
authors: Kreyling
authors: William D
authors: WD
authors: Bennett
mesh_terms: D000336:Aerosols; D002244:Carbon / Q000008:administration & dosage / Q000493:pharmacokinetics; D016503:Drug Delivery Systems; D006801:Humans; D007727:Krypton Radioisotopes; D008168:Lung / Q000378:metabolism*; D008875:Middle Aged; D012123:Pulmonary Ventilation; D011877:Radionuclide Imaging; D015656:Respiratory Mechanics / Q000502:physiology; D012907:Smoking; D013667:Technetium; D014018:Tissue Distribution
chemical_list: D000336:Aerosols; D007727:Krypton Radioisotopes; D013667:Technetium; D002244:Carbon