Carbon Monoxide Headquarters

Acute CO Poisoning:

Comparing Longterm Outcomes of NBO and HBO Therapies:

Study Title:

Hopkins, R.O. and Weaver, L.K.


Undersea & Hyperbaric Medicine, 21 , pg. 17

Abstract (only):
Background: The longterm outcome of patients with carbon monoxide (CO) poisoning is presently not known. Previous studies in the literature that have assessed longterm outcome have only followed subjects who presented with specific neurological and/or cognitive impairments. The purpose of this study was to obtain outcome data on all subjects with acute CO poisoning, over a 3-year period of time (1989-1991).

Materials: A questionnaire was developed to assess outcome in a wide variety of functional categories, including medical, employment, mood, behavioral and cognitive functioning. Ninety-five subjects whom presented with CO poisoning, were treated either with hyperbaric oxygen (HBO), or normobaric oxygen (NBO) and subsequently followed. The questionnaire was administered over the phone.

Results: The time from treatment to follow-up ranged from one-month to 18 months (M = 6.1). Forty-five subjects (47%) were lost to follow-up. Fifty subjects were contacted, 30 of whom were treated with HBO, and 20 treated with NBO. Twenty-three (46%) subjects were normal (HBO = 9, NBO = 14). Twenty-six (52%) subjects reported residual problem(s). Thirteen subjects reported medical problems not related to CO. There was one late death due to CO. The following problems were reported by the subjects (HBO = 21, NBO = 6):

Memory                 17
New Headache            8
New Depression          8
Attention Span          5
Anxiety                 4
Concentration           4
Attention               3
Blurry Vision           3
Family Problems         3
Sleep Disruption        3
Task Frustration        3
Numbness                2
Ageusia                 1
Anosmia                 1
Most patients had returned to work. Four patients lost their jobs following CO poisoning because they were not able to perform at their pre-exposure level.

1) This study demonstrates that a large number of subjects have persistent longterm impairments due to CO poisoning, which adversely affect their quality of life.
2) HBO did not prevent persistent neurologic sequelae.
However, we acknowledge several weaknesses with this study including inconsistent time of follow-up and lack of neuropsychological tests which appear to be sensitive to abnormalitioes due to CO poisoning. We suggest longitudinal follow-up at two weeks, six weeks, six months, and 12 months, in order to determine the behavioral, cognitive and medical outcome in all CO poisoned individuals. Follow-up should include subjective information, assessment of cognitive and behavioral function, assessment for depression and neurological evaluation. A prospective clinical trial designed to measure functional and cognitive outcome to at least one year following CO poisoning could define the magnitude of the problems that we have identified.

Location of Authors:
Department of Psychology, University of Utah, and Hyperbaric Medicine, Critical Care Division, LDS Hospital, Salt Lake City, UT 84143 USA

To Especially Note:

  • The incidence of Persistent Neurologic Sequelae (PNS) was high
  • The residual symptoms are as shown above.
  • Use of HBO did not prevent the development of PNS

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