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Data extraction
The review extracted data from accepted articles using a standardised instrument created
for this assessment. Two independent reviewers examined each article. Discrepancies in
evaluation were discussed and resolved through consensus.
Assessment of quality
All accepted articles underwent an assessment of study quality based on criteria that
focus on important aspects of study design (Table 7). 24,25
Table 7 Domains and levels used in the assessment of methodologic quality.
Randomisation
Adequate Adequate measures to conceal allocations such as central randomisation; serially numbered,
opaque, sealed envelopes; or other descriptions that contain convincing elements of
concealment
Unclear Unclearly concealed trials in which the author failed to describe the method of concealment
with enough detail to determine its validity
Inadequate Method of allocation is not concealed, such as alternation methods or the use of case
numbers
None No randomisation method was employed
Masking Masking strategy applied (triple, double, etc.)
Losses to Follow-up Losses specified.
The review assessed evidence presented in the selected studies and classified it according
to the National Health and Medical Research Council (NHMRC) revised hierarchy of
evidence (Table 8). 26
Table 8 Designation of levels of evidence.
I Evidence obtained from a systematic review of all relevant randomised controlled trials.
II Evidence obtained from at least one properly designed randomised controlled trial.
III-1 Evidence obtained from well-designed pseudo-randomised controlled trials (alternate allocation or some other
method).
III-2 Evidence obtained from comparative studies with concurrent controls and allocation not randomised (cohort
studies), case-control studies or interrupted time series with control group.
III-3 Evidence obtained from comparative studies with historical control, two and more single arm studies or
interrupted time series without a parallel control group.
IV Evidence obtained from case series, either post-test or pre-test and post-test.
Source: NHMRC 26
Assessment of heterogeneity
The review used a two-stage process to examine the heterogeneity of treatment effects.
Firstly, the clinical and epidemiological attributes of the identified research in each
indication category were examined to establish whether they were sufficiently similar to
justify further analysis. If this was the case the second stage of assessment of
heterogeneity moved on to statistical analysis. The review used the Cochran Q statistic 27
to test the hypothesis that the reported treatment effects for each indication were equal.
The Q statistic is known to have low power in detecting heterogeneity. 28 For this reason,
the review specified a Type I error rate of ten percent (α = 0.10) for this test, 29 and
examined Galbraith diagrams 30 and L’Abbé plots 31 generated from the extracted data.
All statistical analyses were performed using Stata version 6.0 (Stata Corporation, College
Station, Texas, USA).
12 Hyperbaric oxygen therapy