title: Positive expiratory pressure changes aerosol distribution in patients with cystic fibrosis.
abstract: OBJECTIVE
  We hypothesized that aerosol distribution in the lungs of patients with cystic fibrosis changes with positive expiratory pressure (PEP).
  
  
  METHODS
  Eight patients were randomized to one of 2 conditions. On one study day, patients inhaled saline aerosol containing 99mtechnetium generated by a Pari LC Plus nebulizer and exhaled through a Pari PEP device. On another day, the same patients exhaled through a low-resistance Pari filter (no PEP). Afterwards, they underwent gamma-camera lung imaging. Images were analyzed for lung deposition fraction, expressed as a percent of the initial nebulizer activity, and deposition pattern, expressed in terms of inner-outer and apical-basal ratios.
  
  
  RESULTS
  Lung deposition fraction was significantly lower with the Pari PEP device; the mean + SD deposition fraction was 6.10 + 3.05% (median 6.20%) with PEP, compared to 10.76 + 4.52% (median 10.32%) (p = 0.0078) without PEP. The inner-outer ratio was 2.01 + 0.69 (median 2.23) with PEP, which was significantly lower than without PEP (2.76 + 1.33, median 2.55) (p = 0.004). The apical-basal ratio was 0.82 + 0.31 (median 0.80) with PEP, which was not significantly different from no PEP (1.00 + 0.49, median 0.90).
  
  
  CONCLUSIONS
  These results indicate that less aerosol is deposited in the lungs of patients with cystic fibrosis when the Pari LC Plus nebulizer is used with the Pari PEP device, as described in these experiments. Nevertheless, aerosol administration with this nebulizer and PEP device also results in a proportional redistribution of aerosol to the peripheral airways, compared to nebulization without the PEP device. The clinical relevance of this subtle redistribution of aerosol in cystic fibrosis patients will probably depend on the drug administered and disease severity.
authors.affiliation: Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland 21287-2533, USA. blaube@jhmi.edu
authors.forename: Beth L
authors.initials: BL
authors.lastname: Laube
authors.forename: David E
authors.initials: DE
authors.lastname: Geller
authors.forename: Ta-Chun
authors.initials: TC
authors.lastname: Lin
authors.forename: Richard N
authors.initials: RN
authors.lastname: Dalby
authors.forename: Marie
authors.initials: M
authors.lastname: Diener-West
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Zeitlin
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000336:Aerosols / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D003550:Cystic Fibrosis / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D015902:Gamma Cameras; D006801:Humans; D008297:Male; D009330:Nebulizers and Vaporizers; D010316:Particle Size; D011175:Positive-Pressure Respiration; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000493:pharmacokinetics; D012129:Respiratory Function Tests; D012965:Sodium Chloride / Q000008:administration & dosage / Q000493:pharmacokinetics; D018709:Statistics, Nonparametric; D016284:Technetium Tc 99m Pentetate / Q000008:administration & dosage / Q000493:pharmacokinetics; D014018:Tissue Distribution
chemical_list: D000336:Aerosols; D019275:Radiopharmaceuticals; D012965:Sodium Chloride; D016284:Technetium Tc 99m Pentetate