In the last few years, we’ve had a little bit of a sea-change in oxygenation during intubation. We’ve stopped relying solely on pre-oxygenation to bridge our patients through apnea, and started providing passive oxygenation during intubation. Usually supplied by high-flow nasal cannula, this takes advantage of physiology and diffusion to distribute oxygen into circulation.
But, as these authors state, the evidence for this practice is spotty – mostly observational evidence from controlled intubation settings. Our critically-ill patients hardly have the same physiology as those undergoing elective airway procedures, and are generally less responsive to oxygenation adjuncts. So, this is the FELLOW trial, a pragmatic, open-label randomized trial comparing apneic oxygenation vs. “usual care” – which was none.
With 150 patients in their intention-to-treat analysis, this cartoon sums up the results sufficiently:
Not much difference!
Their two groups were relatively well-balanced in terms of physiology and airway comorbidities. The intubating operators were reasonably experienced (median >50 intubations), and 2/3rds of the patients were intubated on the first attempt. There were probably no important differences in pre-oxygenation or procedural factors.
But, it is quite a small trial. There are small differences here favoring the apneic oxygenation arm that simply might not reach statistical significance. The exclusion criteria included “if the treating clinicians felt a specific approach to intra-procedural oxygenation or a specific laryngoscopy device was mandated for the safe performance of the procedure”, which could have introduced a selection bias. The open-label effects may or may not be confounding. The ICU environment and exclusion criteria also affect generalizability to the Emergency Department.
In the end, the answer is: apneic oxygenation still probably helps, particularly considering the pre-study evidence favored the intervention, and this one study does not move the needle much. However, the observation here of a clinically unimportant effect size is not unreasonable. If the effect size is small, the cost of an intervention becomes important. However, in this case, the cost is fairly minimal – a small addition to set-up time and procedural complexity. Considering the low cost and the post-test odds still favoring the intervention, it would be erroneous to stop providing apneic oxygenation based on this trial, and further study is indicated.
“Randomized Trial of Apneic Oxygenation during Endotracheal Intubation of the Critically Ill”
http://www.ncbi.nlm.nih.gov/pubmed/26426458
As pointed out on Emcrit- I think the reason why NO-DESAT didn't work is that a lot of patients (about 40%) were not truly apenic- they had BiPAP or were bagged during the axenic period. This is not standard EM practice due to aspiration concerns and we are much more likely to let patients be completely apenic before the blade goes in. I think in this study the BiPAP/BVM served the same purpose as axenic oxygenation. This explains why NO DESAT works so well in my practice (as I rarely bag patients- BiPAP sometimes) but didn't show an effect in the ICU where they know fasting status and are more comfortable with bagging. I would also argue that I care about the rate of desat below 80%- 10% lower incidence in the NO-DESAT group but not statistically significant- perhaps a larger study would show this to be significant?
I'm not exactly certain how to respond to the idea the patients "weren't truly apneic". High-flow preoxyenation during adequate respiration, followed by BVM or BiPAP in the setting of inadequate tidal volume, is a reasonable "usual care" during the pre-laryngoscopy induction/apnea phase. This is outlined in Scott's own Annals article:
http://emcrit.org/wp-content/uploads/2011/10/Preox-annals-article.pdf
Yes, if you don't bag or BiPAP your patients, then I'd probably say your "usual care" doesn't optimize periprocedural oxygenation the way they did in this trial. In that sense, something (NODESAT) is definitely better than nothing!
"In the end, the answer is: apneic oxygenation still probably helps…"
Good to see apneic oxygenation is a life saver.
Sorry to be a bit of a smart ass, but how much does slightly less or more of a transient desaturation really matter. Perhaps there might be the very odd occasion. But my guess is most of the apneic oxygenation debate is a bit of a storm in a tea cup…
Sure, try it… but don't kid yourself that it will make a substantial difference in important patient oriented outcomes.
My question about the PPV isn't that it's not usual care; rather, it's a different, very sick population that required that much PPV (only 77% in control arm, 70% in intervention arm). So not only is this a small study to begin with, but only 40 patients weren't getting active ventilation in during the (non)apneic period.
One takeaway I've had from using nasal ox during laryngoscopy is that it really seems to separate out the truly hypoxic patients, versus the healthy ones that I just let the intern do DL a little too long on….
Where does that leave us? I dunno. It's the sick patients who I'd love to be able to oxygenate the most, and I think this trial tells us it doesn't seem to help in them.
While I agree that it's unlikely to be dangerous and it's just a few simple steps, I also agree with Matt Semler's argument on EMCrit re: the hidden harm of adding one more step to the stressful, busy time around laryngoscopy, which is exactly my argument against cricoid pressure.
I think there are probably sick patients who don't need PPV who still may benefit so until we have a bigger study I think I'll still do it.
"Help" can be clinically unimportant. I mean, we have on-call foot massage in our ED, and it's certainly "helpful", but I don't believe it affects any meaningful patient-oriented outcome. But, it's great for Press-Ganey!
"Help" can also be clinically important in ways that are difficult to measure in patient-oriented outcomes. Take ETCO2 for procedural sedation — the studies "show" all it really does is find subclinical respiratory depression (according to certain bloggers…) but can they capture how much provider stress it removes from the sedation?