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Three Part Question

In [adult patients with carbon monoxide poisoning] does [hyperbaric oxygen when compared to normobaric oxygen] improve [outcome]?

Clinical Scenario

A 55 year old woman has been trapped in a small room in a house fire. COHb levels confirm she has carbon monoxide poisoning. You wonder whether normobaric or hyperbaric oxygen will give her a better outcome.

Search Strategy

Medline using the OVID interface 1966-06/05
[exp Carbon Monoxide Poisoning/ or carbon monoxide poisoning.mp.] AND [hyperbaric oxygen$.mp. or exp Carbon Monoxide Poisoning/ or exp Hyperbaric oxygenation/ or hyperbaric oxygenation$.mp.] LIMIT to human AND English Language AND yr 2002-2005
COCHRANE Database, search for 'hyperbaric oxygen'

Search Outcome

204 relevant papers were found in Medline of which 0 were relevant. 1 review was found from the Cochrane Database.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Juurlink DN. Buckley NA. Stanbrook MB. Isbister GK. Bennett M. McGuigan MA. 2005 UK	Non-pregnant adults acutely poisoned with carbon monoxide Six randomised controlled trials comparing the effectiveness of hyperbaric oxygen (HBO) compared to normobaric oxygen (NBO) for the prevention of neurological sequelae.	Systematic Review	Raphael 1989, 629 patients. Self assessment questionnaire and physical examination by neurologist	No difference in outcome, symptoms present in 32% of patients treated with NBO vs. 32% treated with HBO at one month	Only two of the trials (Scheinkestel 1999 and Weaver 2002) were conducted in a double-blind fashion. The methodological and statistical heterogeneity of the 6 trials renders the analysis difficult to interpret.
			Thom 1995, 65 patients	HBO is of benefit, 7/30 patients in control arm had neurological sequelae vs. 0/30 patients in HBO arm
			Mathieu 1996, 575 patients. Neuropsychological testing at 1,3,6 and 12 months	Statistical difference in neurological symptoms was reported at 3 months (15% with HBO vs. 9% with NBO p=0.016). No significant difference reported at 1, 6 or 12 months.
			Scheinkestel 1999, 230 patients. Mortality and neurological symptoms	NBO is more effective than HBO. No mortality diference at discharge. 34/52 symptomatic in HBO arm vs. 20/34 symptomatic in NBO arm.
			Weaver 2002, 152 patients. Neuropsychological testing at 1, 2, 3, 6, 26 and 52 weeks follow up	No difference between HBO and NBO
			Raphael 2004, self assessment questionnaire and examination by a blinded neurologist at 1 month	No difference in primary outcomes was evident.

Comment(s)

Existing randomised control trials of HBO vs. NBO in the treatment of non-pregnant adults with acute carbon monoxide poisoning provide conflicting results regarding the effectiveness of HBO. Based on the results of these trials HBO cannot be routinely recommended for the treatment of CO poisoning. it is possible that some patients, particularly those with more severe poisoning may derive benefit from treatment but this remains unproven.

Clinical Bottom Line

In an adult patient with carbon monoxide poisoning there is no evidence to suggest hyperbaric oxygen when compared to normobaric oxygen has a better outcome.

References

1. Juurlink DN. Buckley NA. Stanbrook MB. Isbister GK. Bennett M. McGuigan MA. Hyperbaric oxygen for carbon monoxide poisoning. The Cochrane Collaboration 2005, issue 2