Hyperbaric Oxygen Therapy - Hyperbaric Chamber Information ...

Assessment of heterogeneity
All the identified studies were sufficiently similar in clinical and epidemiological
characteristics to allow statistical analysis of heterogeneity to proceed.
The risk for major amputations was studied by all of the eligible reports. The Cochrane
2
Q statistic failed to detect the presence of heterogeneity ( χ df = 3 = 0.
87 , p = 0.833). A
L’Abbé plot and Galbraith diagram (Figure 2) of the measures of effect supported this
conclusion. Similarly sensitivity analyses performed across simple classifications of the
identified studies demonstrated no statistically significant differences in effect sizes. This
2
was the case for sensitivity analyses based on study design (RCTs only: χ df = 1 = 0.
44 , p =
2
0.508), HBOT protocols used (two-phase protocol: χ df = 2 = 0.
68,
p = 0.710), and recent
2
publication (post-1995: χ 0.
53 , p = 0.468).
df = 1 =
Similar results were seen for risk of minor amputations (p = 0.722) and wound healing
(p = 0.462).
In all analyses, the review made the assumption that the study by Doctor et al. 49 was
successful in establishing balanced groups.
HBOT Subjects
z-score (b/se)
.5
.4
.3
.2
.1
0
2.54705
2
0
-2
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0 .1 .2 .3 .4 .5
Comparison Therapy Subjects
.
0 .5 1
weighting factor (1/se)
1.5 2
Figure 2. L’Abbé plot (top) and Galbraith diagram (bottom) of subjects undergoing major
amputation. Numerical symbols in each of the graphs refer to bibliographic citations
found in the text. Sizes of studies in the L’Abbé plot are weighted using the Mantel-
Haenszel method.
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