Journal Club Summary
Casey JD, et al. N Engl J Med. 2019 Feb 28;380(9):811-821.
Methodology Score: 3.5/5
Usefulness Score: 3.5/5
Question and Methods:
Multicenter, unblinded RCT in 7 ICUs comparing rates of hypoxia in patients undergoing BVM vs no ventilation during the period between induction and laryngoscopy.
Findings: Compared to no ventilation group, BVM group had: 3% higher median lowest O2 sat and 11.9% decrease in incidence of O2 sat <80%.
Limitations: Differences between study groups (ie. preoxygenation methods, indications for intubation). No patient-oriented outcomes. Conducted in ICU setting with limits generalizability to the ED setting.
Interpretation: Ventilation in pre-intubation period is balance between hypoxia and aspiration. Consider providing prophylactic ventilation in patients at high-risk of desaturation during the peri-intubation period.
By: Dr. Jim Yang
Adjustment of Confidence Intervals for Interim Analyses
Interim analyses are commonly planned in large studies. This can be useful, for example, to ensure patient safety (either by finding a significant benefit or harm early on), or as a cost saving measure by stopping the study early if there is no statistical probability to find a difference between groups later on. There are caveats to interim analyses. It is possible for a perceived “futile” study to become significant if allowed to continue on (lack of power to find a difference early on). It is also possible to find a significant difference early on by chance alone. Because the likelihood to find a difference by chance alone increases every time you analyze the data, there are strategies to account for this (such as O’Brien Fleming), most of which include raising the bar for statistical significance (i.e. p-value much smaller than 0.05 or using >95%CI instead).