Airway Management Research Update: Who Knew?

One of the best things about EMS is the stuff we learn from each other. Paramedics, doctors, nurses, EMTs—any of our colleagues might pass along a trick, a technique, or even a theory not found in mainstream curricula that enhances our prehospital practice. On days when conventional caregiving is no match for bad luck, sometimes the best medicine is a bolus of “try this.”

Dr. Calvin Brown’s quarterly airway management webinar, presented by Airway World, is a target-rich environment for emergency-medicine pearls that aren’t likely to reach EMS through conventional means—books, lectures, refreshers, etc. The science at these sessions is so cutting-edge, I bet even most anesthesiologists and ED docs aren’t aware of the associated research until months after Dr. Brown’s podcasts. You, on the other hand, are going to hear about a few of these offbeat, but evidence-based, innovations right now.

Turning the O₂ knob as far as it goes

Can you remember a test scenario in any EMS class where the scripted course of action was to crank the O₂ regulator up to 50 liters per minute? I doubt it. Fifteen LPM was the highest prescribed flow rate because that was the most you’d need to keep a nonrebreather reservoir inflated, even on a patient who’s huffing and puffing.

It turns out blowing up the bag isn’t enough to maximize preoxygenation—a critical step in preventing hypoxia during intubation. According to a study of 26 healthy volunteers, the fraction of expired oxygen (FEO₂), a measure of preoxygenation, is 60% higher when the flow is 50 LPM versus 15. That contradicts the notion of wasting O₂ with super-high or flush-flow rates.

Delivering O₂ at 50 LPM isn’t possible with many portable regulators, but you’ll find settings of at least 40 on some. Also, most hospital wall units have small placards with flush-flow rates achieved by twisting the knob past the assumed 15-LPM maximum.

When not to use ketamine

For this part of Brown’s presentation, I had to familiarize myself with the term shock index—the heart rate divided by the systolic blood pressure. A rising shock index indicates deterioration.

It’s important to keep an eye on shock index when considering ketamine as your pre-intubation sedative. Research shows hypotension (< 90 SBP) is 13 times more likely when ketamine is administered to patients with shock indices above 0.9. That’s because ketamine is a catecholamine depletor, and catecholamines are what elevate heart rates in shock states.

The take-home message? Most sedatives can cause some amount of hypotension, but ketamine is more apt to do that in shocky patients.

Visualizing less of the vocal cords

As you prepare to intubate a patient, imagine you gain an unobstructed view of the vocal cords, but can’t quite pass the tube—a possibility with acute airway angles caused by hyper-curved video-laryngoscope blades. What should you do?

I know what I’d do: yank even harder on the handle, thinking I must be looking at some sort of glottic aberration that was mentioned the one time I left medic class early.

I would be wrong. In fact, the proper step would be to relax my death grip on the laryngoscope and settle for a Grade II view, which is the posterior half of the glottic opening and surrounding tissue. According to a study of 163 patients (yes, people analyze these things), I’d save an average of nine seconds by easing back on the blade, realigning the axes, and inserting the tube anterior to the arytenoid cartilages.

I can’t wait to try that one. But wait, I’m not riding anymore. Hmm…

“Max! Here, boy!”

You can view Airway World’s quarterly research updates at https://www.airwayworld.com/webinars/.

Mike Rubin is a paramedic in Nashville, TN, and a member of EMS World’s editorial advisory board. Contact him at mgr22@prodigy.net.