Written by Clay Smith
High-flow nasal cannula (HFNC) compared to bag-valve mask (BVM) ventilation for preoxygenation of critically ill patients did not improve lowest SpO2 but significantly reduced severe complications (SpO2 < 80%, severe hypotension, and cardiac arrest); 6% HFNC vs. 16% BVM, NNT = 10.
Why does this matter?
High flow nasal oxygen delivery for preoxygenation (or apneic oxygenation) has been shown to be effective in adults, in most studies. Yesterday, we reviewed a study showing probable benefit of ApOx in children. Here is some high quality evidence that HFNC is a good way to preoxygenate when intubating.
Improving preox in sick folks
This was a multicenter, unblinded RCT of 184 critically ill adults without profound hypoxia who needed endotracheal intubation. They compared HFNC (60L/min, 100%FiO2 via AIRVO 2) to BVM (self-inflating bag, bag reservoir, tight mask seal) for 4-minutes of preoxygenation. There was no significant difference in the primary outcome of lowest median SpO2: 100% for HFNC, 99% BVM. For desaturation <95%, risk was far less with HFNC than BVM: 12% vs 23%, respectively, NNT = 9. HFNC also markedly reduced the risk of severe adverse outcomes (defined as SpO2 <80%, severe hypotension, and cardiac arrest) compared to BVM: 6% vs 16%, respectively, NNT = 10. The downside was that HFNC may have made intubation more difficult, with more patients having >10 minutes duration of the intubation procedure or ≥3 attempts (10% HFNC vs 1% BVM). By chance, there were more patients with history of difficult intubation in the HFNC group. In the end, it appears HFNC is a low-risk, highly effective way to optimize preoxygenation (and possibly apneic oxygenation) in adults. I don’t see a downside.
Nasal high-flow preoxygenation for endotracheal intubation in the critically ill patient: a randomized clinical trial. Intensive Care Med. 2019 Jan 21. doi: 10.1007/s00134-019-05529-w. [Epub ahead of print]
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Reviewed by Thomas Davis