title: Respiratory system deposition with a novel aerosol delivery system in spontaneously breathing healthy adults.
abstract: BACKGROUND
  Intravenous magnesium sulfate (MgSO(4)) in children and adults with refractory acute asthma is effective, but therapy may be limited by systemic hypotension that might be avoided with the aerosol route. Inhaled MgSO(4) has a relatively high dose (volume) requirement. This, plus the use of inefficient delivery systems, may explain the lack of efficacy of inhaled MgSO(4) in some studies. An in vitro study suggested that the AeroNeb Go with the Idehaler Pocket and a face mask would deliver 16 mg/min of MgSO(4) to the respiratory system in older children, and approximately a fifth for toddlers, but no in vivo data exist.
  
  
  METHODS
  Saline mixed with a radiolabel was used as a proxy for the 100 mg/mL MgSO(4) solution. In 5 adult males the rate of deposition was measured using nuclear medicine techniques. The radiolabel deposition below the vocal cords was converted to the rate of deposition of MgSO(4) and compared to the results from an in vitro model using adult respiratory patterns.
  
  
  RESULTS
  The mean ± SD rate of deposition was 12.6 ± 1.9 mg/min. The reasons for this lower deposition, compared to the in vitro estimate, was most likely the exhalation of anatomical dead space aerosol, which would have been captured on the inspiratory filter in vitro.
  
  
  CONCLUSIONS
  These in vivo data confirm the deposition data predicted in the in vitro study, although caution should be used in extrapolating the results to children. This device appears suitable for the clinical trial of inhaled MgSO(4) in children and adults with refractory asthma.
authors.affiliation: Physiology and Experimental Medicine Research Institute.
authors.forename: Allan L
authors.initials: AL
authors.lastname: Coates
authors.forename: Kitty
authors.initials: K
authors.lastname: Leung
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Chan
authors.forename: Nancy
authors.initials: N
authors.lastname: Ribeiro
authors.forename: Martin
authors.initials: M
authors.lastname: Charron
authors.forename: Suzanne
authors.initials: S
authors.lastname: Schuh
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000336:Aerosols / Q000008:administration & dosage; D001249:Asthma / Q000188:drug therapy*; D002121:Calcium Channel Blockers / Q000008:administration & dosage; D016503:Drug Delivery Systems / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D006801:Humans; D008278:Magnesium Sulfate / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D009330:Nebulizers and Vaporizers; D011877:Radionuclide Imaging; D012137:Respiratory System / Q000000981:diagnostic imaging / Q000187:drug effects; D016896:Treatment Outcome
chemical_list: D000336:Aerosols; D002121:Calcium Channel Blockers; D008278:Magnesium Sulfate
keywords: asthma; inhaled magnesium sulfate; nuclear medicine; pulmonary deposition; respiratory system deposition