title: Enhanced aerosol deposition in the lung with mild airways obstruction.
abstract: We investigated the sensitivity of aerosol deposition to airways obstruction by measuring total deposition fraction of inert aerosol in normal conscious sheep (n = 6) after challenging cholinergic agent, pilocarpine (PL) (0.5 mg/kg intravenously) with and without a prior challenge of beta 2-adrenergic agonist, terbutaline sulfate (TS) (0.025 mg/kg subcutaneously). Aerosol deposition was measured by a light-scattering aerosol photometer in situ while sheep rebreathed 1.0-micron-diameter inert oil droplets from a 0.2-L collapsible bag at a rate of 30 breaths/min. Total accumulated deposition at the fifth breath (AD5) as a percentage of initial aerosol concentration was determined and compared with mean pulmonary airflow resistance (RL). After PL, both AD5 and RL increased significantly from baseline values by 51 +/- 9% and 597 +/- 118% (mean +/- SE), respectively, whereas AD5 and RL decreased significantly by 16 +/- 4% and 34 +/- 6%, respectively after TS (p less than 0.05). After PL subsequent to TS (TS-PL), AD5 increased in all six sheep by 33 +/- 7% from post-TS values (p less than 0.05). However, RL did not change from post-TS values. Greater changes in RL than in AD5 after PL (bronchoconstriction) or TS (bronchodilation) suggest a greater sensitivity of RL than AD5 to airway patency in the large airways. Lack of increase of RL after TS-PL indicates that bronchoconstrictive effect of PL was blocked by prior challenge with TS. Therefore, the increase in AD5 after TS-PL may be related to the peripheral airway obstructions which might have been caused by increased secretions induced by a potent secretagogue PL.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Pulmonary Disease, University of Miami School of Medicine at Mount Sinai Medical Center, Florida.
authors.forename: C S
authors.initials: CS
authors.lastname: Kim
authors.forename: W M
authors.initials: WM
authors.lastname: Abraham
authors.forename: L
authors.initials: L
authors.lastname: Garcia
authors.forename: M A
authors.initials: MA
authors.lastname: Sackner
mesh_terms: D000336:Aerosols; D000402:Airway Obstruction / Q000503:physiopathology*; D000403:Airway Resistance / Q000187:drug effects; D000818:Animals; D005260:Female; D008168:Lung / Q000187:drug effects / Q000503:physiopathology*; D010862:Pilocarpine / Q000494:pharmacology; D012129:Respiratory Function Tests / Q000295:instrumentation / Q000379:methods; D012149:Restraint, Physical; D012756:Sheep; D013726:Terbutaline / Q000494:pharmacology; D013990:Tidal Volume
chemical_list: D000336:Aerosols; D010862:Pilocarpine; D013726:Terbutaline