Hyperbaric Oxygen Therapy for Acute Ischemic Stroke
Hyperbaric oxygen therapy (HBOT) involves the administration of 100% oxygen at pressures >1 atmosphere (101.3 kPa). HBOT greatly increases the partial pressure of oxygen in the blood and tissues and was first proposed in the treatment of ischemic stroke 45 years ago. The improved oxygenation may reduce cerebral edema, decrease lipid peroxidation, inhibit leukocyte activation, and restore the functional blood–brain barrier, all or some of which may promote neuronal survival.
Conversely, oxygen can increase oxidative stress through the production of oxygen free-radical species, and the brain is particularly at risk. HBOT remains an experimental therapy for acute ischemic stroke.
We undertook a systematic review with meta-analysis to evaluate the effectiveness and safety of HBOT as an adjunctive therapy for the treatment of acute ischemic stroke.1
We performed a sensitive electronic search of multiple databases in April 2014. We included all randomized controlled trials that compared the effect of adjunctive HBOT with either no treatment or sham and in which death or functional scales were assessed as outcomes. We used standardized forms to extract the data, and each included trial was assessed for internal validity.
Eleven randomized controlled trials (705 participants) are included in the review, with 7 trials contributing to the quantitative analysis. There were no statistically significant differences in early fatality rate (3–6 months) in those receiving HBOT (relative risk 0.97, 95% CI 0.34–2.75; Figure). The statistical heterogeneity between trials was eliminated by removal of the single trial testing the combination of HBOT and a free-radical scavenger (edaravone) versus edaravone only.
Three of the 7 trials reported improvements in a total of 4 of 19 scale measures of disability, function, or activities of daily living after HBOT. At 1 year the mean Trouillas Disability Scale was lower with HBOT (mean difference [MD] 2.2 points; 95% CI, 0.15–4.3) and the mean Orgogozo Scale was higher (MD 27.9 points; 95% CI, 4.0–51.8). These improvements were not evident in earlier assessments in the relevant trials. One trial used an undefined Neurological Functional Deficit Score and reported an early benefit from HBOT with a mean score at 3 weeks over sham (MD 3 points, 95% CI 0.4–5.6). The same trial reported the mean Barthel Index was higher at 3 weeks (MD 20 points; 95% CI 13.7–26.3).
Implications for Practice
We found limited clinical data, and the evidence is insufficient to confirm that HBOT significantly affects outcomes after acute ischemic stroke. Use of HBOT as routine therapy for people with stroke cannot be justified by this review.
Implications for Research
Given the small number of participants in the trials included, we cannot be certain that a benefit from HBOT has been excluded. More information is needed on the optimal timing of therapy and subset of disease most likely to benefit. The effect of differing oxygen dosage and of other therapies administered simultaneously is not known.
This article is based on a Cochrane Review published in The Cochrane Library 2014, Issue 11 (see www.thecochranelibrary.com for information). Cochrane Reviews are regularly updated as new evidence emerges and in response to feedback, and The Cochrane Library should be consulted for the most recent version of the review.
We acknowledge the support and suggestions of Hazel Fraser and the editors of the Cochrane Stroke Group and thank them for their assistance in the preparation of this review. In particular, we acknowledge the help of Brenda Thomas with developing the search strategy used, and Daniel Rusyniak, Peter Langhorne, Ale Algra, and Steff Lewis for their editorial assistance.
The Cochrane Library is available at: http://www.thecochranelibrary.com/view/0/index.html. Reprints of the full-text version are available online from this site.
- Received January 8, 2015.
- Revision received February 16, 2015.
- Accepted February 18, 2015.
- © 2015 American Heart Association, Inc.