Apneic oxygenation: Everything you know is wrong
Take your time to get that tube smoothly, non-traumatically into trachea on 1st pass
It was during paramedic class, oh so many years ago, when I first heard it: "If you can't get the tube within 30 seconds, stop the attempt and ventilate for a while."
My instructors paraphrased it in more practical terms, admonishing us to hold our breaths when we began an intubation attempt. "When you need to take a breath, so does the patient," they reminded us.
The concept was reinforced during countless NREMT skill stations, where we routinely failed candidates for taking longer than 30 seconds on a single intubation attempt. Those poor candidates trudged the walk of shame back to the routing area to take their places beside the other failed candidates who committed the unpardonable sin of forgetting to say, "I'll have my professional partner hyperventilate the patient while I prepare my equipment."
I was also taught that a nasal cannula can only deliver a maximum of 44 percent oxygen and that non-rebreather masks can provide more than 95 percent oxygen.
Turns out, none of the above was true.
Back then, my instructors didn't spend much time dwelling on concentration gradients and the oxyhemoglobin dissociation curve. It wasn't until years later that I learned that hyperventilation is a bad thing and that an adequately preoxygenated patient takes quite some time to desaturate. If your patient is adequately preoxygenated, you're far more likely to do harm by rushing an intubation attempt to get it done in less than 30 seconds than you are likely to cause a hypoxic state.
In other words, you can afford to take your time.
Current recommendations for preoxygenation prior to ETI are to give at least eight full tidal volume ventilations of 100 percent oxygen via BVM or to apply a non-rebreather mask at 15 lpm for four minutes. That non-rebreather mask, of course, also requires that you maintain adequate airway positioning during that time.
Keep the patient's head elevated so that the external auditory meatus is aligned with the sternal notch. Their facial plane should be parallel with the ceiling and not tilted back.
Preoxygenated with those methods, a healthy adult will take as much as eight minutes to desaturate to a spO2 of less than 90 percent. After that, it gets ugly fast. But even cutting that figure in half for the obese or those with chronic pulmonary pathology, you still have minutes to secure a tube, not seconds.
Still, there's a way to maintain adequate oxygenation during an ETI attempt: Apneic oxygenation using a nasal cannula, an idea espoused by Dr. Richard Levitan, airway management guru and Associate Professor of Emergency Medicine at Jefferson Medical College. As Dr. Levitan explained it in Emergency Physicians Monthly:
While the common perception is that a non-rebreather mask is the pinnacle of oxygen administration, effective FiO2 from these masks may not create optimal pre-oxygenation at flow rates of 15 lpm. This is because the measured inspired oxygen in the hypopharynx with a non-rebreather at 15 lpm is only 60-70%. The reason for this is the patients expired gases are mixing with the applied oxygen, and also because expired gases accumulate in the nasopharynx. Quiet breathing involves flow rates as high as 30 lpm; maximal pre-oxygenation with a loose-fitting non-rebreather may require a flow rate as high as 48 lpm. High flow nasal oxygen has been shown to flush the nasopharynx with oxygen, and then when patients inspire they inhale a higher percentage of inspired oxygen.
To use Dr. Levitan's procedure, simply add a nasal cannula at 15 lpm to your preoxygenation with BVM or non-rebreather mask, and keep it running until you secure a tube and resume ventilation. The nasal cannula will allow you to reach oxygen delivery levels unobtainable with the BVM or non-rebreather alone, and it will provide a pressure gradient that will keep the alveolar capillaries suffused with oxygen for as long as you'll need to secure an airway. In studies, researchers were able to maintain apneic patients' oxygen saturation at 98 percent for up to 100 minutes.
The only drawback is that it requires a second oxygen source, and yes, CO2 buildup is still a concern, but one that can easily be reversed once you've secured a means to ventilate the patient effectively.
Try this in your clinical practice, and buy yourself and your patients some extra time to get that tube smoothly, non-traumatically into the trachea on the first pass.
To learn more about apneic oxygenation and other techniques to maximize preoxygenation, read these two excellent articles:
- NO DESAT (Nasal Oxygen During Efforts Securing A Tube)
- Preoxygenation, Reoxygenation and Delayed Sequence Intubation in the Emergency Department
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