Hyperbaric oxygen therapy for acute domestic carbon monoxide poisoning: two randomized controlled trials. Hyperbaric or normobaric oxygen for acute carbon monoxide poisoning: a randomised controlled clinical trial. Delayed neuropsychologic sequelae after carbon monoxide poisoning: prevention by treatment with hyperbaric oxygen. Trial of normobaric and hyperbaric oxygen for acute carbon monoxide intoxication. Hyperbaric oxygen therapy for cognitive disorders after irradiation of the brain.
Although hyperbaric oxygen therapy (HBO) is broadly used for carbon monoxide (CO) poisoning, its efficacy and practical modalities remain controversial.
                To assess HBO in patients poisoned with CO.
                Two prospective randomized trial on two parallel groups.
                Critical Care Unit, Raymond Poincaré Hospital, Garches, France.
                Three hundred eighty-five patients with acute domestic CO poisoning.
                Patients with transient loss of consciousness (trial A, n = 179) were randomized to either 6 h of normobaric oxygen therapy (NBO; arm A0, n = 86) or 4 h of NBO plus one HBO session (arm A1, n = 93). Patients with initial coma (trial B, n = 206) were randomized to either 4 h of NBO plus one HBO session (arm B1, n = 101) or 4 h of NBO plus two 2 HBO sessions (arm B2, n = 105). PRIMARY ENDPOINT: Proportion of patients with complete recovery at 1 month.
                In trial A, there was no evidence for a difference in 1-month complete recovery rates with and without HBO [58% compared to 61%; unadjusted odds ratio, 0.90 (95% CI, 0.47-1.71)]. In trial B, complete recovery rates were significantly lower with two than with one HBO session [47% compared to 68%; unadjusted odds ratio, 0.42 (CI, 0.23-0.79)].
                In patients with transient loss of consciousness, there was no evidence of superiority of HBO over NBO. In comatose patients, two HBO sessions were associated with worse outcomes than one HBO session. To assess neurological sequelae in patients with all grades of carbon monoxide (CO) poisoning after treatment with hyperbaric oxygen (HBO) and normobaric oxygen (NBO).
                Randomised controlled double-blind trial, including an extended series of neuropsychological tests and sham treatments in a multiplace hyperbaric chamber for patients treated with NBO.
                The multiplace hyperbaric chamber at the Alfred Hospital, a university-attached quarternary referral centre in Melbourne providing the only hyperbaric service in the State of Victoria.
                All patients referred with CO poisoning between 1 September 1993 and 30 December 1995, irrespective of severity of poisoning. Pregnant women, children, burns victims and those refusing consent were excluded.
                Daily 100-minute treatments with 100% oxygen in a hyperbaric chamber--60 minutes at 2.8 atmospheres absolute for the HBO group and at 1.0 atmosphere absolute for the NBO group--for three days (or for six days for patients who were clinically abnormal or had poor neuropsychological outcome after three treatments). Both groups received continuous high flow oxygen between treatments.
                Neuropsychological performance at completion of treatment, and at one month where possible.
                More patients in the HBO group required additional treatments (28% v. 15%, P = 0.01 for all patients; 35% v. 13%, P = 0.001 for severely poisoned patients). HBO patients had a worse outcome in the learning test at completion of treatment (P = 0.01 for all patients; P = 0.005 for severely poisoned patients) and a greater number of abnormal test results at completion of treatment (P = 0.02 for all patients; P = 0.008 for severely poisoned patients). A greater percentage of severely poisoned patients in the HBO group had a poor outcome at completion of treatment (P = 0.03). Delayed neurological sequelae were restricted to HBO patients (P = 0.03). No outcome measure was worse in the NBO group.
                In this trial, in which both groups received high doses of oxygen, HBO therapy did not benefit, and may have worsened, the outcome. We cannot recommend its use in CO poisoning. Carbon monoxide (CO) poisoning is a major clinical problem. The risk of morbidity and the most effective treatment have not been clearly established. We measured the incidence of delayed neurologic sequelae (DNS) in a group of patients acutely poisoned with CO and tested the null hypothesis that the incidence would not be affected by treatment with hyperbaric oxygen (HBO).
                We conducted a prospective, randomized study in patients with mild to moderate CO poisoning who presented within 6 hours. Patients had no history of loss of consciousness or cardiac instability.
                The incidence of DNS was compared between groups treated with ambient pressure 100% oxygen or HBO (2.8 ATA for 30 minutes followed by 2.0 ATA oxygen for 90 minutes). DNS were defined as development of new symptoms after oxygen treatment plus deterioration on one or more subtests of a standardized neuropsychologic screening battery.
                In 7 of 30 patients (23%), DNS developed after treatment with ambient-pressure oxygen, whereas no sequelae developed in 30 patients after HBO treatment (P < .05). DNS occurred 6 +/- 1 (mean +/- SE) days after poisoning and persisted 41 +/- 8 days. At follow-up 4 weeks after poisoning, patients who had been treated with ambient pressure oxygen and had not sustained DNS exhibited a worse mean score on one subtest, Trail Making, compared with the group treated with HBO and with a control group matched according to age and education level. There were no differences in scores between the control group and the hyperbaric oxygen group.
                DNS after CO poisoning cannot be predicted on the basis of a patient's clinical history or CO level. HBO treatment decreased the incidence of DNS after CO poisoning. The value of hyperbaric oxygen in the treatment of acute carbon monoxide intoxication was assessed in 629 adults who had been poisoned at home in the 12 h before admission to hospital. In patients without initial impairment of consciousness (group A) the effect of 6 h of normobaric oxygen (NBO) (group A0, n = 170) was compared with that of 2 h of hyperbaric oxygen (HBO) at 2 atmospheres absolute (ATA) plus 4 h NBO (group A1, n = 173). At the 1 month follow-up 66% of A0 and 68% of A1 patients had recovered. In patients with initial impairment of consciousness the effect of one session of HBO (group B1, n = 145) was compared with that of two sessions (group B2, n = 141); all group B patients also received 4 h of NBO. At 1 month of follow-up 54% group B1 and 52% group B2 patients had recovered. The 7 patients left with neuropsychiatric sequelae (3 B1, 4 B2) and the 4 who died (2 B1, 2 B2) had all presented with coma. HBO was not useful in patients who did not lose consciousness during carbon monoxide intoxication, irrespective of their carboxyhaemoglobin level, nor were two sessions of HBO in patients who sustained only a brief loss of consciousness. The prognosis is poorest for those presenting with coma; the trial needs to be pursued in this group of patients until the power of the study is sufficient to demonstrate the value or otherwise of HBO. Analysis of the feasibility and effect of hyperbaric oxygen treatment (HBO) on cognitive functioning in patients with cognitive disorders after irradiation of the brain.
                Seven patients with cognitive impairment after brain irradiation, with an interval of at least 1.5 years after treatment, were treated with 30 sessions of HBO in a phase I-II study. A comprehensive neuropsychological test battery was performed before treatment, at 3 and 6 months thereafter. Patients were randomized into an immediate treatment group and a delayed treatment group. The delayed group had a second neuropsychological test at 3 months without treatment in that period and started HBO thereafter.
                All eligible patients completed the HBO treatment and the extensive neuropsychological testing. One out of seven patients had a meaningful improvement in neuropsychological functioning. At 3 months there was a small, but not significant benefit in neuropsychological performance for the group with HBO compared to the group without HBO treatment. Six out of seven patients eventually showed improvement after HBO in one to nine (median 2.5) of the 31 tests, although without statistical significance.
                HBO treatment was feasible and resulted in a meaningful improvement of cognitive functioning in one out of seven patients. Overall there was a small but not significant improvement.
Existing randomised trials do not establish whether the administration of HBO to patients with carbon monoxide poisoning reduces the incidence of adverse neurologic outcomes. Additional research is needed to better define the role, if any, of HBO in the treatment of patients with carbon monoxide poisoning. This research question is ideally suited to a multi-center randomised controlled trial.