Journal Club Summary
Question & Methods: The authors wanted to summarize the best available evidence of RCTs to guide rational use of O2 therapy.
Findings: Their review of over 16 000 patients provides high-quality evidence that liberal supplemental O2 increases in-hospital mortality (RR1.21), mortality at 30 days (RR 1.14) and mortality at longest follow-up (RR1.10).
Limitations: Heterogeneity of definitions, un-blinded studies, and description of duration of therapy; practically, the density of the paper will likely limit its dissemination.
Interpretation: High-quality evidence indicates that liberal O2 increases mortality among a broad range of illnesses and that this likely has a dose response relationship; specific trials are needed to further clarify.
Epi Lesson – Clinical vs Statistical Heterogeneity
A meta-analysis may attempt to address a compelling clinical dilemma. One of the key questions to ask when appraising meta-analyses is whether the pooling of the included studies is appropriate. Clinical heterogeneity reflects clinical differences between study populations, the intervention, co-interventions and/or outcomes when pooling studies in meta-analysis. This is distinct from statistical heterogeneity which can be determined by visually assessing the forest plot, measuring the I2 statistic or the Cochran’s Q. Always ask yourself if the meta-analysis is combining apples with apples.
By: Dr. Lisa Calder