Author: Tucker Mathews, MD

Edition 4: Airways, airways, airways!

Paper 1:

Mohr NM, Santos Leon E, Carlson JN, Driver B, Krishnadasan A, Harland KK, Ten Eyck P, Mower WR, Foley TM, Wallace K, McDonald LC, Kutty PK, Santibanez S, Talan DA; Project COVERED Emergency Department Network. Endotracheal Intubation Strategy, Success, and Adverse Events Among Emergency Department Patients During the COVID-19 Pandemic. Ann Emerg Med. 2022 Nov 3:S0196-0644(22)01117-9. doi: 10.1016/j.annemergmed.2022.09.013. Epub ahead of print. PMID: 36336542; PMCID: PMC9633323.

Overview: Multicenter prospective cohort at 20 EDs from May to December 2020 comparing intubation events in patients suspected or confirmed of having COVID with those that weren’t suspected or confirmed. They basically enrolled specific providers, who then reported the cases that occurred in which they performed the actual intubation.

Notable results:

-They tracked all of the usual characteristics of each intubation.

-One weird subtlety was how they labeled patients in regards to COVID status. It wasn’t always based on a test result. If the clinician had suspicion, they were put into a COVID+ group (and vice versa; if the clinician thought they didn’t have COVID, they were put in a COVID- group) regardless of their eventual COVID test result after the fact.

-Total of 3,435 intubations, 565 of which were known or suspected COVID positive.

-The COVID patients were generally older and more likely to be intubated for acute respiratory failure

-83% video laryngoscopy, and about half (56%) were performed by residents.

-There were no differences between the groups in medication choice, though there was actually more VL usage in COVID patients.

-COVID patients were pre-oxygenated a little more aggressively with NIMV or HFNC.

-Overall first-pass success was 87%, and didn’t differ between the groups.

-Peri-intubation adverse events happened more commonly in the COVID patients (35%) compared to the non-COVID (19%). This was usually hypoxia, which isn’t shocking given the reason for intubation in most of these COVID patients.

-Interestingly, adverse events were more common when the airway was anticipated beforehand to be difficult by the clinician.

Thoughts: It’s an impressive collection of data. Because we’re only looking at these select providers, it’s obviously a pretty limited sample, but still interesting. Even with their attempts at covariate analysis, it’s just hard to compare these two groups of patients and assume that the only real differences are COVID status to explain the change in adverse events. So if anything, what I really take from this is just confirmation of what we know, that COVID respiratory failure patients are sick, and have lots of adverse events surrounding their intubations. I’m also not totally sure what to make of the fact that the low anticipated airway difficulty patients had more adverse events, but maybe there just wasn’t enough prep there. Or maybe, it indicates that those patients had intubation delayed until later moments (this was around the time we were being told to avoid intubation when possible in COVID) when they were more at risk of complication, whereas with the patients that were anticipated to be difficult, the provider secured the airway earlier on in their decompensation.

Overall though it’s interesting just to see the data on how these patients were taken care of during the beginnings of COVID, when there wasn’t a lot of supported information to instruct us on how to manage them.

Summary: In this prospective cohort study from late 2020, COVID+ patients seem to have higher rates of adverse events during intubation.

Paper 2:

van Schuppen H, Wojciechowicz K, Hollmann MW, Preckel B. Tracheal Intubation during Advanced Life Support Using Direct Laryngoscopy versus Glidescope® Videolaryngoscopy by Clinicians with Limited Intubation Experience: A Systematic Review and Meta-Analysis. J Clin Med. 2022 Oct 26;11(21):6291. doi: 10.3390/jcm11216291. PMID: 36362519; PMCID: PMC9655434.

Overview: This is a systematic review and meta-analysis (SRaMA) comparing direct laryngoscopy with video laryngoscopy in providers with limited experience in tracheal intubation.

Notable results:

-Limited experience was defined as less than 10 intubations per year (a very odd definition since that’s like 1 a month), but for the most part the studies used students.

-Primary outcome was first pass success rate. Secondary outcomes were time needed for successful intubation, and duration of interruption of chest compressions during CPR

-They identified 4 clinical trials and 20 manikin trials, for a total of 525 patient intubations and 2547 manikin intubations. Importantly, only one of the clinical trials was performed during CPR, and the other three were all in the OR.

-It’s sort of weird how they report the first pass success data, because they use a relative risk, where the “risk” is VL usage. With that definition, the pooled RR for first pass success was 1.61 for the 4 clinical studies, with moderate evidence, and 1.17 in the manikin studies, with low evidence. So that indicates the superiority of VL.

-There was also moderate evidence for VL having decreased time until intubation and less time with paused chest compressions (though that is from only one study).


There just aren’t many studies here using actual patients, and so it feels odd to conduct all of these calculations on only 4 clinical studies, with the rest in manikins. That being said, the overall pooled data definitely suggests that in those with minimal intubation experience, VL is superior to DL—at least for their initial attempts at intubating. To me, this is actually an important area of discussion, because there should really be some sort of evidence-based suggestion for Emergency Medicine residency programs for how to teach intubation strategy to incoming residents. And if the data suggest that starting with VL (in a hyperangulated form, as they are for these studies) is the optimal starting format, then it makes sense to me to have trainees learn to excel in that mode, before trying to branch out into other modes, such as standard geometric VL, and DL. The authors seem to be more interested in how these data apply in the prehospital setting though (which is also really important and interesting).

Summary: Current available data suggest that inexperienced providers should probably be using video laryngoscopy to optimize their intubations.

Paper 3:

Hayes-Bradley C, Tarrant M. Rocuronium ≤1.5 mg/kg versus >1.5 mg/kg and inadequate paralysis in prehospital and retrieval intubation: A retrospective study. Emerg Med Australas. 2022 Dec;34(6):892-897. doi: 10.1111/1742-6723.14008. Epub 2022 Jun 1. PMID: 35649634.

Overview: This was a retrospective review of all prehospital RSI cases from the Greater Sydney Area Helicopter EMS using rocuronium as a paralytic after an encouragement to increase the dose from 1.5 mg/kg to 2 mg/kg due to concerns over inadequate paralysis.

Notable results:

-It sounds like there are physicians on these runs.

-This wasn’t a protocol change, but instead more of a recommendation that caused increased doses to be used.

-They tried to exclude cases where there was some indication that the IV blew.

-Inadequate paralysis was defined as free-text documentation by the provider of skeletal muscle activity.

-There were 211 patients who received doses less than 1.5 mg/kg, and 384 who received greater than 1.5 mg/kg. 5 of the low dose patients were inadequately paralyzed, compared to 2 of the higher dose group (2.4% vs 0.5%)

-Interestingly, all of the inadequate paralysis cases were traumas

-Weights were all estimated

-Their secondary outcome of percentage of grade 1-2 laryngoscopy was similar, at 88.6% in the low-dose group versus 92.4% in the high-dose group.

-They state that the event rate was too low to perform statistics on…

Thoughts: Not really sure what the EMS situation is in that region, and if this is just one of many groups, or if it’s representative of all EMS runs in the greater Sydney region. They basically had concerns as a group over inadequate paralysis, and so independent of the study, they had tried to protocolize an increased rocuronium dose. After the fact, they looked at the data that became this publication. There wasn’t one specific timepoint in which the doses changed though, so they were unable to perform a time series analysis. What’s obviously interesting, is that their initial dose of 1.5 mg/kg is already more than what is frequently recommended (1.2 mg/kg).

It’s possible that the physician gave a lower dose of the paralytic for a reason (or a higher dose, for that matter), but it’s still some fairly decent data. I feel like in my practice, I split RSI patients into two groups: those who I worry will not be able to effectively circulate the drug, and so I give extra to, and those who can effectively circulate. In the former group, most people are probably already using increased paralytic dosing, and so the data probably would need to be separated between those two groups. But it’s definitely a topic that you could perform an RCT on to better investigate, though you would need some massive sample sizes due to how low the event rates are. I’m also not sold that their chart review methods would pick up on all of the cases of inadequate paralysis. I can’t see a physician reporting some vocal cord movements—though perhaps that level of incomplete paralysis wouldn’t clinically matter. They also aren’t really able to (or don’t try to) look at time to paralysis and time to ETT placement with this data, which would also seem to be variables potentially affected by inadequate paralytic dosing.

Summary: All in all, there isn’t much evidence of danger to providing higher paralytic doses, and given the potential detriments to doses too low, it probably makes sense to overshoot. This study doesn’t show anything with statistical significance and probably has too many holes to really take any conclusions from, but it’s an important topic and the authors do a good job of presenting the data they have, and not trying to overstep their study’s limitations.

Paper 4:

Wetsch WA, Schroeder DC, Herff SJ, Böttiger BW, Wenzel V, Herff H. Identification of the Optimal Position of a Nasal Oxygen Cannula for Apneic Oxygenation: A Technical Simulation. J Clin Med. 2022 Nov 17;11(22):6809. doi: 10.3390/jcm11226809. PMID: 36431286.

Overview: Apneic oxygenation has been proposed as a method to delay the onset of hypoxia during endotracheal intubation, with a traditional nasal cannula approach as the common method, though evidence suggests that deeper oxygen delivery locations have increased efficacy. This study utilized a validated airway manikin to investigate the degrees of hypoxia between differing locations of an apneic oxygenation cannula.

Notable results:

-So it sounds like they just left the manikin without respirations otherwise, and watched the oxygen drop from 100% over 20 minutes.

-For oxygenation they used 4 L/min, and placed the cannula at the nose entrance, through the nose with the tip at the soft palatine, and at the base of the tongue (it’s not clear to me how exactly they did this)

-In the absence of any apneic oxygenation, the manikin desaturated to 53% at 20 minutes

-They found that the group with the cannula at the base of the tongue had just about no desaturation over the 20 minutes. The soft palatine group performed well but was slightly worse.

-The nasal cannula group dropped to 87% after 20 minutes

Thoughts: I just don’t know what to make of this model. It seems pretty hard to replicate the actual anatomy and physiology of a living airway with a manikin, and the fact that it only desaturated to 53% after 20 minutes isn’t overly convincing. They also provided almost no information showing the actual cannula and better describing the oxygenation. Like, why were there no pictures? It’s also interesting to me that they settled on 4L/min as the flow rate. They talk a bit about their rationale, basing it off of some other studies, but I also don’t understand why they wouldn’t also just use a couple of other flow rates to compare and prove that it is an optimal flow rate on which to perform their analysis.

Summary: It makes a lot of sense to me that oxygenating through the nose during apnea isn’t going to provide much benefit, especially when the patient is paralyzed and the soft tissues of the palate lose tone. And so if there is a better location to try and provide oxygen, I’m all ears, but I’m not sure this study does anything to convince me of any specific practice change.

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