title: Rapid elimination of CO through the lungs: coming full circle 100 years on.
abstract: At the start of the 20th century, CO poisoning was treated by administering a combination of CO(2) and O(2) (carbogen) to stimulate ventilation. This treatment was reported to be highly effective, even reversing the deep coma of severe CO poisoning before patients arrived at the hospital. The efficacy of carbogen in treating CO poisoning was initially attributed to the absorption of CO(2); however, it was eventually realized that the increase in pulmonary ventilation was the predominant factor accelerating clearance of CO from the blood. The inhaled CO(2) in the carbogen stimulated ventilation but prevented hypocapnia and the resulting reductions in cerebral blood flow. By then, however, carbogen treatment for CO poisoning had been abandoned in favour of hyperbaric O(2). Now, a half-century later, there is accumulating evidence that hyperbaric O(2) is not efficacious, most probably because of delays in initiating treatment. We now also know that increases in pulmonary ventilation with O(2)-enriched gas can clear CO from the blood as fast, or very nearly as fast, as hyperbaric O(2). Compared with hyperbaric O(2), the technology for accelerating pulmonary clearance of CO with hyperoxic gas is not only portable and inexpensive, but also may be far more effective because treatment can be initiated sooner. In addition, the technology can be distributed more widely, especially in developing countries where the prevalence of CO poisoning is highest. Finally, early pulmonary CO clearance does not delay or preclude any other treatment, including subsequent treatment with hyperbaric O(2).
authors.affiliation: Department of Anesthesiology, University Health Network, University of Toronto, Toronto, Canada. joe.fisher@utoronto.ca
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Fisher
authors.forename: Steve
authors.initials: S
authors.lastname: Iscoe
authors.forename: Ludwik
authors.initials: L
authors.lastname: Fedorko
authors.forename: James
authors.initials: J
authors.lastname: Duffin
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000627:therapeutic use*; D002248:Carbon Monoxide / Q000097:blood; D002249:Carbon Monoxide Poisoning / Q000473:pathology / Q000628:therapy*; D002263:Carboxyhemoglobin / Q000378:metabolism; D005260:Female; D005315:Fetal Diseases / Q000097:blood; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000009:adverse effects; D007700:Kinetics; D008168:Lung / Q000503:physiopathology; D010100:Oxygen / Q000008:administration & dosage / Q000627:therapeutic use*; D011247:Pregnancy; D012123:Pulmonary Ventilation / Q000187:drug effects; D012756:Sheep; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D002248:Carbon Monoxide; C011700:carbogen; D002263:Carboxyhemoglobin; D010100:Oxygen