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J Clin Epidemiol. 2014 Jan;67(1):65-72. doi: 10.1016/j.jclinepi.2013.08.004. Epub 2013 Nov 1.

Using GRADE for evaluating the quality of evidence in hyperbaric oxygen therapy clarifies evidence limitations.

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Division of Preventive, Occupational and Aerospace Medicine, Mayo Clinic, 200 1st Street, Rochester, MN 55902, USA; Knowledge and Evaluation Research Unit, Mayo Clinic, 200 1st Street, Rochester, MN 55902, USA. Electronic address:

Erratum in

  • J Clin Epidemiol. 2014 Oct;67(10):1178.



The current evidence rating for hyperbaric oxygen therapy indications uses the American Heart Association system, which mainly depends on the study design.


We systematically reviewed the literature and applied the Grading of Evidence, Assessment, Development and Evaluation (GRADE) approach to the main patient-important outcomes in each indication.


We included 17 systematic reviews that synthesized 44 randomized trials and 131 observational studies enrolling 8,145 participants. The quality of evidence for seven indications with category A was high (1), moderate (2), low (2), and very low (2); for 10 indications with category B, it was moderate (1), low (5), and very low (4); and for 1 indication with category C, it was high. The quality of evidence was rated down for the risk of bias and imprecision for most indications and rated up because of large effect size for some indications. Most discrepant ratings were in the indications of decompression illness (C, high), carbon monoxide poisoning (A, very low), and later presentations of idiopathic sudden hearing loss (A, very low).


The GRADE approach uncovered factors affecting the quality of evidence that were otherwise implicit. Knowing these factors can influence clinicians' confidence in applying hyperbaric oxygen therapy and orient the research agenda.


American Heart Association; Clinical practice guidelines; GRADE; Hyperbaric oxygen therapy; Quality of evidence; Systematic review; Umbrella systematic review

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