Airway Management Research Update: Counter Weight

Have any of you practiced endotracheal intubation on obese manikins? I didn’t even know such training tools existed until I saw an ad for Fat Old Fred, a corpulent, polyurethane torso that looks much more like my sickest patients than Resusci Anne and her lean, anatomically ambiguous cousins ever did.

If you can’t book time with Fred, Dr. Calvin Brown’s quarterly webinars are the next best way to fine tune airway management for obese patients—a prospect that always upped my catecholamine quotient when I was in the field. Brown’s year-end podcast focused on these weighty topics:

Delivering apneic oxygenation orally

Last March, the doctor introduced the term apneic oxygenation (ApOx) to describe passive delivery of O₂ down the tracheobronchial tree. The idea is to bathe the glottic inlet of your apneic patient with as much oxygen as you can force through a nasal cannula—at least 10 liters per minute. Some of that O₂ will make its way into the lungs, thereby lengthening desaturation time during intubation attempts.

If you think high-flow O₂ through a nasal cannula is radical, wait ‘til you hear how to handle ApOx if the nasal route isn’t available:

1. Get a right-angle endotracheal (RAE) tube. Never seen one? Neither had I before Brown’s webcast. The one he used looked like a mid-sized, uncuffed pediatric tube bent at much more than a right angle—150 degrees at least.
2. Insert the distal end along the patient’s inner cheek toward the tonsil of your choice.
3. Attach the proximal end to an oxygen source. No, you don’t have to do that through a BVM adapter.
4. Crank up the O₂ and let it blow toward the glottis. Some of it will get into the lungs. Yes it will.

According to a September 2016 Australian study of obese patients, those who received ApOx via an RAE tube took more than twice as long to desaturate than those who got no ApOx. In Brown’s opinion, oral or nasal apneic oxygenation should be routine.

RSI drug-dosing for the morbidly obese

Should two common RSI meds—succinylcholine, a neuromuscular blocker, and etomidate, an induction agent—be administered to obese patients based on standard weight-related dosing? Yes and no.

Brown says 1.5 mg/kg of succinylcholine is usually appropriate for obese individuals because acetylcholine activity rises with body weight, and you don’t want to have a partially paralyzed patient. With etomidate, though, Brown recommends basing the usual 0.3 mg/kg-dose on lean body weight, the formula for which modifies total body mass according to height and gender.

You may want to review RSI procedures and even drug math with your colleagues; Brown quoted a study that concluded succinylcholine doses are incorrect 56% of the time and etomidate doses are wrong 24% of the time.

Predicting success of non-invasive positive-pressure ventilation

If you’re a fan of the APGAR scale, you’re going to love HACOR, as in Heart rate, Acidosis, Consciousness, Oxygenation and Respiratory rate. HACOR is a predictor of non-invasive positive-pressure ventilation (NIPPV) success. In general, patients with a HACOR score greater than or equal to five after one hour of NIPPV are over four times more likely to be intubated than those with HACORs less than five. You’ll find HACOR details here.

Airway research article of the year

This being the final airway webinar of 2016, attendees voted on the best research article presented this year. The winner was “Flush Rate Oxygen for Emergency Airway Preoxygenation” by Driver, Prekker, et al. You’ll find my comments about that paper here.

See all of Airway World’s quarterly research updates at https://www.airwayworld.com/webinars/.

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