title: Normocapnia improves cerebral oxygen delivery during conventional oxygen therapy in carbon monoxide-exposed research subjects.
abstract: OBJECTIVE
  We determine whether maintaining normocapnia during hyperoxic treatment of carbon monoxide-exposed research subjects improves cerebral oxygen delivery.
  
  
  METHODS
  This experiment used a randomized, single-blinded, crossover design. We exposed 14 human research subjects to carbon monoxide until their carboxyhemoglobin levels reached 10% to 12%. We then treated each research subject with 60 minutes of hyperoxia with or without normocapnia. Research subjects returned after at least 24 hours, were reexposed to carbon monoxide, and were given the alternate treatment. Relative changes in cerebral oxygen delivery were calculated as the product of blood oxygen content and middle cerebral artery velocity (an index of cerebral blood flow) as measured by transcranial Doppler ultrasonography.
  
  
  RESULTS
  Maintaining normocapnia during hyperoxic treatment resulted in significantly higher cerebral oxygen delivery compared with standard oxygen treatment (P <.05; 95% confidence interval at 60 minutes 2.8% to 16.7%) as a result of the prevention of hypocapnia-induced cerebral vasoconstriction and more rapid elimination of carbon monoxide due to increased minute ventilation.
  
  
  CONCLUSIONS
  If severely poisoned patients respond like our research subjects, maintaining normocapnia during initial hyperoxic treatment of carbon monoxide poisoning may lead to increased oxygen delivery to the brain. Determining the effect of such a change in conventional treatment on outcome requires clinical studies.
authors.affiliation: Department of Anesthesia, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Joshua
authors.initials: J
authors.lastname: Rucker
authors.forename: Janet
authors.initials: J
authors.lastname: Tesler
authors.forename: Ludwik
authors.initials: L
authors.lastname: Fedorko
authors.forename: Akinori
authors.initials: A
authors.lastname: Takeuchi
authors.forename: Luciana
authors.initials: L
authors.lastname: Mascia
authors.forename: Alex
authors.initials: A
authors.lastname: Vesely
authors.forename: Sasha
authors.initials: S
authors.lastname: Kobrossi
authors.forename: Arthur S
authors.initials: AS
authors.lastname: Slutsky
authors.forename: George
authors.initials: G
authors.lastname: Volgyesi
authors.forename: Steve
authors.initials: S
authors.lastname: Iscoe
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Fisher
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D002249:Carbon Monoxide Poisoning / Q000188:drug therapy* / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage* / Q000097:blood / Q000627:therapeutic use; D016037:Single-Blind Method
chemical_list: D010100:Oxygen