Carbon Monoxide Headquarters

Chronic CO Poisoning:

A Case Series:

Methods: Patients who sought care for fatigue, headache or at least two of the symptoms listed in Table 1, where the symptoms continued for at least one month, and where improvement in their condition occurred after identification and removal of a source of CO were included. Patients were given questionnaires asking about defective equipment, duration of symptoms, and recovery time. Household pet behavior was also surveyed. Six pets had died and six others had had symptoms conceivably related to CO exposure (Table 3).

Results: In a series of 26 patients, 15 patients were exposed to 9 defective gas furnaces, 3 to faulty oil furnaces, 7 to malfunctioning automobile exhaust systems, and 1 to a defective bus exhaust system.
COHb was measured in 14 patients withing 5 hours of suspected CO exposure. The COHb levels ranged from 8.8% to 36.8%, the mean equaling 15.1%. Mean values for auto exhaust victims was 14.%, while that for faulty furnaces was 15.8%. Three patients presented in coma - they had CO symptoms for days - weeks prior to discovery.
Most patients reported fatigue and headache. A majority also reported having "trouble thinking", dizziness, a pounding heart, and shortness of breath. Nine patients had impaired visual acuity. Diarrhea and abdominal pain were also frequently described, as were chest pain, paresthesias, and "vague spells".

  • The time patients' continued to report symptoms following termination of CO exposure varied. For 4 patients it was 1 week or less. For 1 patient it was 1-2 weeks. For 2 patients it was 2 weeks. For 6 patients it was 2-4 weeks. For 4 patients it was 4 weeks, or 4-6 weeks. For 1 patient it was 2-8 weeks. For 2 patients it was 4-8 weeks. For 2 patients it was 8 weeks. For 4 patients it was 12 weeks.
  • The important point in these data is that the symptoms resulting from chronic CO poisoning did not disappear immediately at the end of the exposure. For some patients the residual effects, as judged by these authors, persisted for quite a long time, ie. up to 12 weeks = 3 months.

    Discussion and Comment: They state that clues that assist in differentiating (chronic) CO poisoning from depression and other conditions are the health of pets (see Canaries & Mice as sentinels) and other family members, a negative social history and the presence of other unusual symptoms. "Impaired visual acuity, which was the presenting complaint in 3 patients, should alert a clinician to the possibility of CO poisoning if a potential source is present." Actually, there are a number of other visual conditions that result during and after CO poisoning. They correctly state that "symptoms have failed to correlate well with the level of COHb".

  • The authors mention the case of a family of 5 in a home with a faulty gas furnace. The wife, a homemaker with on-going exposure to CO, became almost completely disabled. the husband's work performance declined, and the children's school work deteriorated. The family members' vague symptoms and impaired cognition initially misled physicians. After her condition improved in the hospital, the mother had a relapse. Only when other family members home for Christmas vacation began to note similar symptoms and when symptoms developed in the patient's mother after she came to stay with the family was the correct diagnosis of a toxic home environment made.
  • Page 54, bottom, right corner contains a glaring typo/error seen elsewhere in medical books - "Promptly collecting a serum specimen after exposure is, therefore, a critical factor in interpreting ............" Of course, blood serum contain little CO; virtually all of the blood CO is contained in the red blood cells, so whole blood is required to make the measurement. They are correct - blood samples for the COHb measurement must be taken in a timely manner.

    Problems with Study: There are several weaknesses in the study -

  • It was not considered that longterm residual symptoms might result; eg. "three patients were eliminated from the study because they had symptoms that persisted more than 6 months after the suspected source of CO had been repaired". This same mistake was made in a 1958 study (Katz, M., Carbon monoxide asphyxia: a common clinical entity, Canad. Med. Assoc. J., 78, 182-185).
  • The most sensitive diagnostic tool in chronic CO poisoning, ie. neuropsychological testing, was not done. The common medical tests done by Kirkpatrick and by other physicians untrained in CO poisoning (urinalysis, complete blood counts, blood chemistries, chest X-rays, etc.) are of no value in getting at the residual effects.

    Kirkpatrick, J.N. (1987) Occult Carbon Monoxide Poisoning. The West. J. Med., 146 (Jan.), pgs. 52-56.


    ...... last changed 07/02/01

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