title: Effect of a spacer on pulmonary aerosol deposition from a jet nebuliser during mechanical ventilation.
abstract: BACKGROUND
  Several factors have been identified which improve nebulised aerosol delivery in vitro. One of these is the addition of a spacer to the ventilator circuit which improves aerosol delivery from a jet nebuliser to a model lung by approximately 30%. The current study was designed to demonstrate whether similar improvements could be demonstrated in vivo.
  
  
  METHODS
  Ten patients (seven men) were studied during mechanical ventilation (Siemens Servo 900C) after open heart surgery. Aerosol was delivered using a Siemens Servo 945 nebuliser system (high setting) driving a System 22 Acorn jet nebuliser (Medic-Aid) containing 3 ml technetium-99m labelled human serum albumin (99mTc-HSA (50 micrograms); activity in the first nebulisation, 90 MBq; in the second nebulisation, 185 MBq). Central and peripheral lung aerosol deposition and the time to complete deposition were measured using a gamma camera and compared when the nebuliser was connected to the inspiratory limb using a simple T-piece or a 600 ml spacer.
  
  
  RESULTS
  The addition of the spacer increased total lung deposition (mean (SD) percentage initial nebuliser activity) from 2.2 (0.7)% to 3 (0.8)%. There was no difference in the time required to complete nebulisation (18.2 min v 18.3 min respectively for T-piece and spacer) or in the retention of activity in the nebuliser (46.2% v 47.1% respectively).
  
  
  CONCLUSIONS
  The combination of a spacer with a jet nebuliser increased lung deposition by 36% in mechanically ventilated patients and is a simple way of increasing drug deposition or reducing the amount of an expensive drug required for nebulisation.
authors.affiliation: Intensive Therapy Unit, St Thomas' Hospital, UMDS, London, UK.
authors.forename: C J
authors.initials: CJ
authors.lastname: Harvey
authors.forename: M J
authors.initials: MJ
authors.lastname: O'Doherty
authors.forename: C J
authors.initials: CJ
authors.lastname: Page
authors.forename: S H
authors.initials: SH
authors.lastname: Thomas
authors.forename: T O
authors.initials: TO
authors.lastname: Nunan
authors.forename: D F
authors.initials: DF
authors.lastname: Treacher
mesh_terms: D000336:Aerosols; D000368:Aged; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009330:Nebulizers and Vaporizers; D010316:Particle Size; D011877:Radionuclide Imaging; D012121:Respiration, Artificial; D013668:Technetium Tc 99m Aggregated Albumin; D014980:Xenon Radioisotopes
chemical_list: D000336:Aerosols; D013668:Technetium Tc 99m Aggregated Albumin; D014980:Xenon Radioisotopes