title: Helium-oxygen reduces the production of carbon dioxide during weaning from mechanical ventilation.
abstract: BACKGROUND
  Prolonged weaning from mechanical ventilation has a major impact on ICU bed occupancy and patient outcome, and has significant cost implications.There is evidence in patients around the period of extubation that helium-oxygen leads to a reduction in the work of breathing. Therefore breathing helium-oxygen during weaning may be a useful adjunct to facilitate weaning. We hypothesised that breathing helium-oxygen would reduce carbon dioxide production during the weaning phase of mechanical ventilation.
  
  
  METHODS
  We performed a prospective randomised controlled single blinded cross-over trial on 19 adult intensive care patients without significant airways disease who fulfilled criteria for weaning with CPAP. Patients were randomised to helium-oxygen and air-oxygen delivered during a 2 hour period of CPAP ventilation. Carbon dioxide production (VCO2) was measured using a near patient main stream infrared carbon dioxide sensor and fixed orifice pneumotachograph.
  
  
  RESULTS
  Compared to air-oxygen, helium-oxygen significantly decreased VCO2 production at the end of the 2 hour period of CPAP ventilation; there was a mean difference in CO2 production of 48.9 ml/min (95% CI 18.7-79.2 p = 0.003) between the groups. There were no significant differences in other respiratory and haemodynamic parameters.
  
  
  CONCLUSIONS
  This study shows that breathing a helium-oxygen mixture during weaning reduces carbon dioxide production. This physiological study supports the need for a clinical trial of helium-oxygen mixture during the weaning phase of mechanical ventilation with duration of weaning as the primary outcome.
  
  
  BACKGROUND
  ISRCTN56470948.
authors.affiliation: Intensive Care Unit, Royal London Hospital, Whitechapel, London, E1 1BB, UK. Gordon.Flynn@sesiahs.health.nsw.gov.au
authors.forename: Gordon
authors.initials: G
authors.lastname: Flynn
authors.forename: Gerlinde
authors.initials: G
authors.lastname: Mandersloot
authors.forename: Marie
authors.initials: M
authors.lastname: Healy
authors.forename: Mark
authors.initials: M
authors.lastname: Saville
authors.forename: Daniel F
authors.initials: DF
authors.lastname: McAuley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D018592:Cross-Over Studies; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage*; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods; D016037:Single-Blind Method; D015300:Ventilator Weaning / Q000379:methods*; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D006371:Helium; D010100:Oxygen
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