Let Apneic Oxygenation Reign!

We have talked about this topic briefly in the past but it is extremely important and deserves more dedicated attention.  Past mantra has dictated using a bag-valve mask (BVM) whenever a patient was thought to not be breathing adequately, or even not breathing at all.  Current evidence emphasizes the danger of the BVM and its inappropriate use.  The BVM can be summarized nicely: 1) It increases intrathoracic pressure thus decreasing preload and coronary artery perfusion, 2) opens the lower esophageal sphincter(even if you are good at ventilating) causing a high risk for vomiting from gastric insufflation, 3) causes over-distention of the alveoli resulting in oxygen shunting and decreased capillary PaO2. and 4) decreases cerebral blood flow. So what can we do to ensure oxygenation in those patients who just don’t require a BVM?  Apneic oxygenation!

The most common time the apneic oxygenation strategy will be employed is during the preoxygenation period and peri-intubation period of airway management.  The principles of apneic oxygenation may also be applied to patients who require supplemental oxygen but may not be able to be intubated at the time (i.e., predicted difficult airway or RSI meds are not available).  The goal is to maintain a SpO₂ > 93% without using a BVM.  If the patient is unconscious during preoxygenation, this can be accomplished with a nasopharyngeal airway (NPA), nonrebreather (NRB) and high-flow nasal cannula (HFNC) set to at least 15 Lpm.  To review, the purpose of preoxygenation is to provide nitrogen washout.  As we know, nitrogen is the most common atmospheric gas and also predominates in your lungs.  If you remove the nitrogen by flooding the airway, including the dead space, with 100% O2 you can increase the functional reserve capacity and buy yourself time and reassurance during the apneic period of intubation. 

The best way to provide oxygenation during the apneic period of intubation is obviously to continue oxygenation.  Place an NPA (or two, yes two, NPAs) and passively oxygenate past the tongue through the glottis.  HFNC may actually provide bubbles or assist in visualization of the trachea; voila you have your view!  Through the use of HFNC during the apneic period of intubation the alveoli will continue to take up oxygen despite a lack of diaphragmatic movement or lung expansion.  Ideally the patient should remain in the upright 20 degree position ensuring that the airway remains patent with an NPA, OPA, jaw-thrust, head-tilt-chin-lift or, preferably, a combination to allow oxygen gas to pass down the nasopharynx into the deeper airway structures and then to the alveoli for passive diffusion.

Recent evidence has reviewed the effectiveness of the HFNC when used in the apneic period of intubation using RSI.  The study was conducted by an Australian helicopter emergency medical service (HEMS).  The HEMS service consisted of a physician and paramedic.  Intubation attempts were split evenly between the physician and paramedic in the pre-intervention arm of the study but favored the paramedics during the institution of apneic oxygenation.   They reviewed RSI intubations pre and post implementation of an apneic oxygenation protocol.  They had a significant decrease in desaturation during intubation in the group that received apneic oxygenation (22.6% to 16.5%).  They also noted a decrease in cardiac arrests (5.6% to 1.4%) and episodes of bradycardia (7% to 1.4%) related to desaturation during intubation after apneic oxygenation was implemented.  In conclusion, avoid the BVM whenever possible and always use a HFNC during intubation. 

So here is what I do EVERY TIME I am getting ready to intubate.  (Not in this order)

1. Have a BVM ready with PEEP valve on at all times. 
2. Have suction ready. 
3. Quantitative ETCO₂ ready to place on ETT.  (Remember, it needs to “zero” to the atmosphere first anyway.)
4. Nasal cannula at least 15 LPM or as high as you can go. 
5. Apply NRB at 100% over nasal cannula
6. Bag only if RR<4 and SpO₂ <93%.  If RR>4 and SpO₂ <93% use oxygen for 3 MINUTES to see if saturation will come up.  If it does not come up… you can ventilate with BVM slowly (no more than 6 times per minute)

Bonus:  If systolic BP is less than 90 mmHg, add…

1. IV fluid bolus as fast as possible
2. Push-dose Epi 10 µg/min until SBP >90 mmHg

References

Weingart, SD. “Preoxygenation, Reoxygenation, and Delayed Sequence Intubation in the Emergency Department.” J Emerg Med 2010.

Weingart, SD, Levitan, RM. “Preoxygenation and Prevention of Desaturation During Emergency Airway Management.” Ann Emerg Med 2011.

Wimalesena Y, Burns B, Reid C, Ware S, Habiq K. “Apneic Oxygenation Was Associated With Decreased Desaturation Rates During Rapid Sequence Intubation by an Australian Helicopter Emergency Medicine Service.” Ann Emerg Med 2014.