title: Ventilation distribution in rats: Part I--The effect of gas composition as measured with electrical impedance tomography.
abstract: The measurement of ventilation distribution is currently performed using inhaled tracer gases for multiple breath inhalation studies or imaging techniques to quantify spatial gas distribution. Most tracer gases used for these studies have properties different from that of air. The effect of gas density on regional ventilation distribution has not been studied. This study aimed to measure the effect of gas density on regional ventilation distribution.
  
  
  METHODS
  Ventilation distribution was measured in seven rats using electrical impedance tomography (EIT) in supine, prone, left and right lateral positions while being mechanically ventilated with either air, heliox (30% oxygen, 70% helium) or sulfur hexafluoride (20% SF6, 20% oxygen, 60% air). The effect of gas density on regional ventilation distribution was assessed.
  
  
  RESULTS
  Gas density did not impact on regional ventilation distribution. The non-dependent lung was better ventilated in all four body positions. Gas density had no further impact on regional filling characteristics. The filling characteristics followed an anatomical pattern with the anterior and left lung showing a greater impedance change during the initial phase of the inspiration.
  
  
  CONCLUSIONS
  It was shown that gas density did not impact on convection dependent ventilation distribution in rats measured with EIT.
authors.affiliation: Paediatric Critical Care Research Group, Paediatric Intensive Care Unit, Mater Children's Hospital, South Brisbane, QLD, Australia. k.dunster@qut.edu.au
authors.forename: Kimble R
authors.initials: KR
authors.lastname: Dunster
authors.forename: Marlies
authors.initials: M
authors.lastname: Friese
authors.forename: John F
authors.initials: JF
authors.lastname: Fraser
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Cowin
authors.forename: Andreas
authors.initials: A
authors.lastname: Schibler
mesh_terms: D000818:Animals; D017097:Electric Impedance; D045853:Exhalation / Q000187:drug effects; D005260:Female; D005740:Gases / Q000737:chemistry* / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging; D008297:Male; D012123:Pulmonary Ventilation / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014054:Tomography
chemical_list: D005740:Gases