Weaver LK, Hopkins RO, Chan KJ, et al. Hyperbaric oxygen for acute carbon monoxide poisoning. N Engl J Med. 2002 Oct 3;347(14):1057-67.
What we already know about the topic: Carbon monoxide poisoning is responsible for about 40,000 visits to emergency departments every year in the U.S. Patients who survive the initial insult are vulnerable to cognitive sequelae, which generally occur within 20 days of exposure. Hyperbaric oxygen therapy is one potential treatment modality for CO poisoning.
Why this study is important: In this study, the authors investigate whether simply giving a patient hyperbaric oxygen therapy decreases the rate of cognitive sequelae after CO poisoning. It is one of the first articles to support the use of hyperbaric oxygen as a treatment modality.
Brief overview of the study: In this study, 156 patients with CO poisoning (elevated carboxyhemoglobin level, elevated ambient CO concentration, or obvious CO exposure plus other symptoms) were randomized to receive either hyperbaric O2 or normobaric O2 (76 patients in each arm). Every patient had three chamber sessions over 24 hours, either with hyperbaric or normobaric O2. Patients completed a battery of neuropsychological tests before therapy, after the first and third chamber sessions, and again at 2 weeks, 6 weeks, 6 months, and 12 months. The primary outcome was the incidence of cognitive sequelae 6 weeks after therapy. Cognitive sequelae were significantly less frequent at 6 weeks, 6 months, and 12 months in the hyperbaric group.
Limitations: The normobaric group had a higher rate of cerebellar dysfunction before intervention. Also, the study was not designed to determine how much hyperbaric therapy (i.e. the number of sessions) is necessary to experience a benefit.
Take home points: This article suggests that in patients suffering from acute carbon monoxide poisoning, undergoing three sessions of hyperbaric oxygen therapy appears to decrease the risk of experiencing cognitive sequelae. While side effects such as barotrauma and hyperoxic seizures are possible risks of hyperbaric therapy, only one patient in this study had TM rupture (although seven experienced anxiety that caused premature cessation of treatment). The most recent ACEP clinical policy on CO poisoning, released in January 2017 (https://www.acep.org/Physician-Resources/Policies/Clinical-policies/Clinical-Policy-COPoisoning/), suggests that ED physicians should use hyperbaric therapy or high-flow normobaric therapy for acute CO patients. This is a level B recommendation.