We wanted to compare the safety and effectiveness of hyperbaric oxygen therapy (HBOT) versus no HBOT (either no treatment or an ineffective intervention designed to mimic the true treatment) for treating people who had suffered an acute ischaemic stroke.
Hyperbaric oxygen therapy (HBOT) is a treatment designed to increase the supply of oxygen to the part of the brain affected by stroke and to reduce the extent of irreversible damage. HBOT involves people breathing pure oxygen in a specially designed chamber (such as those used for deep sea divers with the bends) for a period of about an hour and a half each day for 10 to 20 days.
We identified 11 studies, involving 705 participants, up to April 2014. All studies included adult participants (41% female) who had suffered an acute stroke within the past two weeks, although most studies enrolled participants within three days of the stroke. All trials evaluated the addition of HBOT to standard practice for study participants. Most trials reported the number of deaths and some measure of functional ability, although the actual measures used varied considerably, making comparisons between trials difficult. Follow-up periods varied from 90 days to one year.
Too few patients have been studied to say whether HBOT decreases the chance of dying, and only three trials have suggested improvement in the ability to do everyday tasks. Overall, little evidence is currently available to support the use of HBOT for people with stroke.
Quality of the evidence
In general, the quality of the evidence was moderate, given the small numbers of participants and the many different instruments used to estimate the quality of life and the functional ability of participants. The methodology used in many of these trials was poorly described, making a good estimate of the reliability of the evidence difficult. We could pool data only for the chance of dying after the stroke, and although no evidence suggested that HBOT reduced the chance of death following a stroke, the confidence we have in this result is relatively low. We have not excluded the possibility that HBOT may be harmful or beneficial.
We found no good evidence to show that HBOT improves clinical outcomes when applied during acute presentation of ischaemic stroke. Although evidence from the 11 RCTs is insufficient to provide clear guidelines for practice, the possibility of clinical benefit has not been excluded. Further research is required to better define the role of HBOT in this condition.
Most cases of stroke are caused by impairment of blood flow to the brain (ischaemia), which results in a reduction in available oxygen and subsequent cell death. It has been postulated that hyperbaric oxygen therapy (HBOT) may reduce the volume of brain that will die by greatly increasing available oxygen, and it may further improve outcomes by reducing brain swelling. Some centres are using HBOT routinely to treat people with stroke. This is an update of a Cochrane Review first published in 2005.
To assess the effectiveness and safety of adjunctive HBOT in the treatment of people with acute ischaemic stroke.
We searched the Cochrane Stroke Group Trials Register (last searched April 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (April 2014), MEDLINE (1966 to April 2014), EMBASE (1980 to April 2014), the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1982 to April 2014), the Database of Randomised Controlled Trials in Hyperbaric Medicine (DORCTIHM) (searched April 2014) and the reference lists of articles. We handsearched relevant publications and contacted researchers to identify additional published and unpublished studies.
Randomised controlled trials (RCTs) that compared the effects of adjunctive HBOT versus those of no HBOT (no treatment or sham).
Three review authors independently extracted data, assessed each trial for internal validity and resolved differences by discussion.
We included 11 RCTs involving 705 participants. The methodological quality of the trials varied. We could pool data only for case fatalities. No significant differences were noted in the case fatality rate at six months in those receiving HBOT compared with the control group (risk ratio (RR) 0.97, 95% confidence interval (CI) 0.34 to 2.75, P value 0.96). Four of 14 scale measures of disability and functional performance indicated improvement following HBOT, for example, the mean Trouillas Disability Scale score was lower with HBOT (mean difference (MD) 2.2 point reduction with HBOT, 95% CI 0.15 to 4.3, P value 0.04), and the mean Orgogozo Scale score was higher (MD 27.9 points, 95% CI 4.0 to 51.8, P value 0.02).