title: Carboxyhemoglobin half-life in carbon monoxide-poisoned patients treated with 100% oxygen at atmospheric pressure.
abstract: OBJECTIVE
  There are large reported differences for the carboxyhemoglobin (COHb) half-life (COHb t(1/2)) in humans breathing 100% atmospheric O(2) following CO inhalation in tightly controlled experiments compared to the COHb t(1/2) observed in clinical CO poisoning (range, 36 to 131 min, respectively). Other reports have suggested that the COHb t(1/2) may be affected by gender differences, age, and lung function. We wished to test the hypothesis that the COHb t(1/2) might also be influenced by CO poisoning vs experimental CO exposure, by a history of loss of consciousness (LOC), concurrent tobacco smoking, and by PaO(2). The purpose of the present study was to measure the COHb t(1/2) in a cohort of CO-poisoned patients and to determine if those listed factors influenced the COHb t(1/2).
  
  
  METHODS
  Retrospective chart review from 1985 to 1995. We calculated the COHb t(1/2) of CO-poisoned patients who were treated with high-flow supplemental atmospheric pressure O(2) delivered by nonrebreather face mask or endotracheal tube.
  
  
  METHODS
  Hyperbaric medicine department of a tertiary-care teaching hospital.
  
  
  METHODS
  Of 240 CO-poisoned patients, 93 had at least two COHb measurements > 2% (upper limit of normal) with recorded times of the measurements, permitting calculation of the COHb t(1/2).
  
  
  RESULTS
  The COHb t(1/2) was 74 +/- 25 min (mean +/- 1 SD) with a range from 26 to 148 min. By stepwise multiple linear regression analysis, the PaO(2) influenced the COHb t(1/2) (R(2) = 0.19; p < 0.001), whereas the COHb t(1/2) was not influenced by gender, age, smoke inhalation, history of LOC, concurrent tobacco smoking, degree of initial metabolic acidosis (base excess), or initial COHb level.
  
  
  CONCLUSIONS
  The COHb t(1/2) of 93 CO-poisoned patients treated with 100% O(2) at atmospheric pressure was 74 +/- 25 min, considerably shorter than the COHb t(1/2) reported in prior clinical reports (approximately 130 +/- 130 min) and was influenced only by the patient's PaO(2).
authors.affiliation: Hyperbaric Medicine and Pulmonary Division, LDS Hospital, Salt Lake City, UT 84143, USA. lweaver@ihc.com
authors.forename: L K
authors.initials: LK
authors.lastname: Weaver
authors.forename: S
authors.initials: S
authors.lastname: Howe
authors.forename: R
authors.initials: R
authors.lastname: Hopkins
authors.forename: K J
authors.initials: KJ
authors.lastname: Chan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002249:Carbon Monoxide Poisoning / Q000097:blood / Q000628:therapy*; D002263:Carboxyhemoglobin / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D003128:Coma / Q000097:blood / Q000628:therapy; D005260:Female; D006207:Half-Life; D006801:Humans; D007223:Infant; D008297:Male; D008657:Metabolic Clearance Rate / Q000502:physiology; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010102:Oxygen Inhalation Therapy; D012907:Smoking / Q000009:adverse effects / Q000097:blood
chemical_list: D002263:Carboxyhemoglobin; D010100:Oxygen