(Last Updated On: December 4, 2015)

Article
Randomized Trial of Apneic Oxygenation during Endotracheal Intubation of the Critically Ill.

Why!?
Airway management is a cornerstone of emergency medicine and critical care medicine.
Patients who require either aggressive oxygenation or airway protection (and to a lesser extent, others with indications for endotracheal intubation) are at risk for hypoxia during Efforts Securing A Tube.

A relatively recent technique, dubbed NODESAT (Nasal Oxygen During Efforts Securing A Tube) gained popularity over the past few years based on surgical data and anecdotal reports. The theory is that 15L/min nasal cannula is applied and left on during a patients resuscitation and intubation. The nasal oxygen at high flow washes out the posterior oropharynx and may even provide some PEEP (up to 5-7cmH20, with a closed mouth). This has led to decreased rates of hypoxia during laryngoscopy but a clinical trial in the critically ill had not been performed until recently.

Background, Context, & Motivation
I have been using the NODESAT technique with anecdotal success. Depending on the clinical site I have been working at, I have been met with some resistance from the support staff, confused as to why we would do this. I wanted to see if non-surgical literature might support the practice in the emergency department. Can nasal oxygenation provide a measurable benefit during laryngoscopy?

Design
Single center, non-blinded, randomized, open-label, parallel-group, pragmatic trial of 150 patients 18 years and older randomized in a 1:1 ratio. Patients with planned awake intubations and patients with hyper-emergent laryngoscopy (such that they could not be randomized) were excluded.

The exact intervention was 15L/min by nasal cannula during apnea. All other factors for intubation (method of preoxygenation, type of laryngoscope, induction agents, etc.) were left up to the decisions of the treating team.

Outcomes
Primary:
-Lowest measured SpO2 between induction and two minutes post-ET tube placement.

Secondary:
-Incidence of hypoxemia (<90%)
-Incidence of severe hypoxemia (<80%)
-Desaturation at all (change in SpO2 of more than 3%)
-Cormack-Lehane grade of glottis view
-Incidence of first pass success
-Number of attempts
-Time from induction to intubation
-Need for additional equipment or operators
-Incidence of non-hypoxemia complications

Findings
Primary outcome:
-Lowest SpO2 with apneic oxygenation was 92%. Without? 90% Not statistically significant.

Secondary outcomes:
-No differences despite looking at higher O2 requirements pre-intubation, BMI, other reasons for difficult intubation,

Limitations of study/Discussion
This was a very well done study with a few limitations. Most importantly is the high rate of patients with shunt physiology (at least one-third of patients were requiring non-invasive positive pressure oxygenation/ventilation prior to endotracheal intubation). These patients are not expected to benefit from apneic oxygenation. Why?

Passive gas exchange happens during apnea. As blood passes by open alveoli, oxygen is absorbed into the blood stream. Carbon dioxide is released, but at a rate of 1/25th that of the absorption of oxygen. This creates a relative vacuum and oropharyngeal gas is pulled into the alveoli. If the oropharynx is full of oxygen (by nasal cannula), oxygen will be continuously pulled into the open alveoli. However, patients with shunt physiology (pneumonia, ARDS, pulmonary edema, diffuse alveolar hemorrhage) do not readily participate in this passive gas exchange. These patients require positive pressure oxygenation/ventilation (CPAP/BPAP).

Secondly, there is no mention of maintenance of airway patency during apnea (jaw thrust, oral/nasal airway devices). This is also required to ensure gas flow to the hypopharynx, as otherwise the tongue and other soft tissues may obstruct. That being said, the operators were very good at laryngoscopy and preparation. The authors note that compliance with standards of preparation was very high, perhaps mitigating any need for the buffer of apneic oxygenation.

Thirdly, they were good at preparation but what does that mean? Recall they excluded patients with such emergent need for endotracheal intubation that they could not be randomized. For better or for worse, these patients that were excluded likely represent the Emergency Department population more accurately.

Fourthly, in regards to the population, yes, it is not an Emergency Department population. No trauma patients, no acute overdoses, etc.

Fifthly, all these patients got a lot of oxygen:
“ The AO group was getting 15LNC on top of a non-rebreather or BIPAP or bag-valve-mask but its not like in the usual care group their preoxygenation device (BIPAP, NRB, etc) was REMOVED at induction.” – M.W. Selmer, lead author.

Summary
Safe but ineffective in this population.

Application to our practice
A very well done trial in a setting that is often hard to control for: the critically ill.
They did all sorts of subanalysis (which is hard to do with a relatively small but not tiny trial) and could not find any subgroup in which this is most helpful.
You are ultimately justified in not using this technique if you feel it gets in the way, and, in fact, that is the lead author’s current opinion. In an EMCRIT interview (see link for nice commentary from Critical Care Medicine fellow) he notes that he used to do it but no longer will because it’s “just another thing to do” that doesn’t seem to help, so he’d rather focus on getting his tools in order, communicating with the team, etc.

My practice: Given the opportunity, I will still utilize NODESAT. Why?

1) I still believe it is likely helpful in patients without obvious shunt physiology.
2) It is just nicer not hearing “95%…94%…93%…” while you are focusing on laryngoscopy. Would you find a difference in an RCT of having the unit team members greet you with a smile every morning or with a scowl? Probably not but I bet you’d prefer the former just for ease of practice.
3) These patients received excellent preoxygenation and while this is an admirable goal it is not always easy to get in the ED (or the ICU for that matter, depending on where you are). I think the apneic oxygenation is still helpful in less-than-ideal circumstances.
4) In reality I ask out loud “Is there a second available oxygen port for nasal oxygen in addition to the bag-valve mask?” Most of the time no one knows, or it’s not set up, or they’ve already used it to secure the ventilator; in these settings I feel justified (sort of) in letting it go and moving on with the rest of the procedure.