Carbon Monoxide Headquarters

Chronic CO Poisoning:

Retrospective Chart Review Study:

Demonstration of substantial persistent neurological sequelae (PNS) in a case series following chronic CO exposure.

A series of patients who were chronically exposed to CO were enrolled in the study. Data collected included CO air samples, initial carboxyhemoglobin (COHb) levels, initial treatment rendered, subjective symptoms, and objective findings on neuropsychologic testing (NPT).

  • Chronic exposure was defined as lasting more than one week.
  • PNS were defined as CNS symptoms and/or abnormalities on NPT persisting for more than 3 months after the CO exposure.


  • 94 patients with CO poisoning were evaluated from Jan., 1995 - Dec., 1997.
  • 38 patients had acute exposures and 56 had chronic exposures to CO.
  • Of the 56 patients with chronic exposures, 23 developed PNS.
  • This included 8 men & 15 women, ages 8 - 58 years of age.
  • Initial COHb levels of the 23 were 0.4 - 5.8%.
  • Only 1 of the 23 patients was treated with hyperbaric oxygen.
  • 17 of the 23 patients had NPT done; 15/17 were abnormal.
  • PNS included headache, fatigue, irritability, difficulty concentrating, and impaired memory.
  • 15 of the 23 patients were followed for at least 12 months.
  • All 15 were still symptomatic 1 year post-exposure.

    PNS do occur following chronic exposure to CO, even with low apparent blood CO levels.

    From: Bayer, M.J., Orlando, J., McCormick, M.A., Weiner, A., Deckel, A.W. (1998) Persistent neurological sequelae following chronic exposure to carbon monoxide. Carbon Monoxide: The unnoticed poison of the 21st century, Satellite Meeting, IUTOX VIIIth International Congress of Toxicology, Dijon, France, July 3-4, 1998, Pg. 179.

    ...... last changed 04/16/99

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