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There should be an image of Morpheus from “The Matrix” in his cool sunglasses asking us: “What if I told you that the way you were taught to confirm ET tube placement is not reliable?”
Perhaps a better way to say it is that there are better ways to confirm that your tube is in the right place with less confounders and complication. A better way is less prone to human error and bias. A better way that is qualitative and has international endorsement as “the way” it should be done–perhaps even be evidence-based.
In 2022, Chrimes et al. published a landmark, practice-changing paper on the prevention of unrecognized esophageal intubation.1
This is a consensus paper from representatives within the airway management community the world over that provides specific guidance that answers the question: “When should we pull the tube?” This guideline is endorsed by many airway management societies to include the Difficult Airway Society, and the Canadian Airway Focus Group. Notably, Martin Bromiley is a member of the Project for Universal Management of Airways (PUMA) advisory group, as are several other known experts in emergency airway management.1
Which is to say, I’ll see your paramedic instructor and raise you international experts in airway management when it comes to the topic of prevention of esophageal intubation.
For this article we will expand on the practice of waveform, qualitative capnography as the gold-standard of endotracheal tube confirmation and recreate the “Swiss cheese” model of how esophageal intubations happen in the first place.
The Problem of Esophageal Intubation
This is largely considered a “never event” in all contexts of emergency medicine and anesthesia – yet is still concerningly prevalent in the literature. Russotto et al. studied 2,964 intubation cases from 197 institutions in 29 different countries found that 5.9% of the intubations were found in the esophagus, 70% of which did not use waveform capnography to confirm placement.
The danger of esophageal intubation is well documented and is well known in the various communities that practice emergency airway management, but Mort et al. provides us with just how bad the problem can be:3
- 5x increase in critical hypoxemia
- 16x increase in aspiration
- 14x increase in post-intubation cardiac arrest
Each of these are independently associated with morbidity and mortality in airway management. The NAP4 study, performed in 2011, highlights some of this morbidity and mortality. A total of 207 airway management cases were reviewed and found the following:4
- 38 resulted in a fatality directly attributed to the airway management.
- Aspiration was a primary complication in 25 cases and was cited as the most common cause of death in this study group.
- 27 cases from the ICU and ED resulted in brain death.
Preventing Esophageal Intubation
There is some inherent risk of adverse events in airway management. It is a worthy pursuit to place an endotracheal tube in the trachea on the first attempt. But as with anything where humans are charged with operating under pressure, sometimes we can get it wrong. But we can mitigate the risk of accidental placement of an airway in the esophagus. The literature supports, overwhelmingly, two initiatives; limiting the number of intubation attempts and video laryngoscopy.
Sackles’ landmark study of the association of adverse events and intubation attempts showed us that there is still a 14% rate of adverse events even with first pass success.5 But they did find an interesting correlation between the number of attempts and the number of times a tube was placed in the esophagus.5
This stems from the pressure that comes with “the need to intubate” and aiming for the first site that appears to be the trachea. Systems or organizations can defeat this time pressure issue with simple protocols that limit the number of intubation attempts. If we use the Sackles paper as a guide, that will limit total intubation attempts to two before using a supraglottic device or emergency procedure to secure the airway.5
The other initiative that can aid prehospital teams in avoidance of esophageal tube placement is video laryngoscopy (VL). While the data cannot prove a distinct and statistically significant superiority of VL over direct laryngoscopy (DL) in overall success or first pass success, it does show a dramatic reduction in the number of esophageal intubations.6
In another study, Sackles and Kovacs show an over 50% reduction in the number of esophageal intubations when the operator uses VL vs. DL.6 Routine use of VL as the primary intubating technique is the number two recommendation by the PUMA advisory group for the reduction of esophageal intubations.1
This recommendation comes second only to the use of waveform capnography for tube confirmation. Said another way, VL is only #2 because you cannot have two #1’s on a list.
Putting a system in place with the proper equipment that aids in avoidance of esophageal intubation can help us combat unrecognized esophageal placement. It is that simple. If it can be prevented at the outset, then it is not a worry later in the patient’s clinical course.
Recognizing Esophageal Intubation
While it is considered a “never event” esophageal intubation does happen, and when it does, prehospital teams must be able to quickly and accurately identify it. Traditional training approaches tube confirmation mostly from a clinical assessment point of view. Paramedics are generally taught to listen to breath sounds, listen over the epigastrium, look for misting in the tube, and look for chest rise and fall to confirm that an ET tube is in the correct place or not. Later, waveform and colorimetric capnography was added as a confirmatory element of the clinical assessment. Current recommendations refute the utility of these when compared to qualitative, waveform capnography.
Can these clinical assessment findings confirm a tube is in the trachea? Yes. But what they do not accomplish is definitively exclude esophageal placement. These assessment findings can be found in both tracheal intubation and esophageal intubation. They are neither sensitive nor specific to one or the other. They are also highly prone to various cognitive biases that can lead clinicians to believe that a tube is in the correct place when it is in fact malpositioned.1
The PUMA group offers four alternative methods to confirm tube placement, we will highlight the three that are applicable to the prehospital arena:1
- Revisualization of the tube via VL.
- Ultrasound
- Esophageal detector device.
Waveform capnography (WFC), on the other hand, is the gold standard for tube confirmation and is quite sensitive and specific for exhaled carbon dioxide. As in near 100% sensitive and specific.7 In a study of prehospital intubations in 2005, it was revealed that in patients where ETco2 was used there were zero unrecognized esophageal intubations.
In those where ETco2 was not utilized, 23% were found to have an unrecognized esophageal intubation.7 In the NAP4 study, the lack of use of capnography was a large contributing factor in 82% of cases that resulted in brain damage and/or death.4
How do we use this tool to the greatest effect and not fall victim to biases? WFC, while beneficial and proven to work as intended, is not impervious to human factors. Those human factors look like clinicians who see ETCo2 waveforms and a number on the monitor and assume “the tube is good” when in fact it may be sitting supraglottic or deep in the right mainstem.
The PUMA group provides six areas of trouble shooting the waveform (printable and reproducible versions of this list and the accompanying graphics can be found at https://www.universalairway.org/downloads):1
Tube is Correctly Placed
- A normal appearing 4 phase waveform is present.
- An attenuated tracing is present that is gradually improving to a normal appearing waveform.
- An attenuated tracing that is explained by clinical presentation, e.g. an intubated patient who is in shock that has poor cardiac output will generate a waveform but may generate lower than normal values.
Tube is Malpositioned
An inconsistent or chaotic appearing waveform that is unrelated to ventilation.
- A waveform that is gradually decreasing in amplitude.
- An attenuated tracing that cannot be explained by clinical presentation.
Responding to the Waveforms
The ETCo2 should grab the clinician’s attention that something is wrong with the tube and prompt them to actively exclude the possibility of an unrecognized esophageal intubation. Active exclusion is the process of visually ascertaining the position of the tip of the tube. The primary recommendation for accomplishing this is to revisualize the glottic opening via VL with a second trained provider to confirm placement.
If placement cannot be confirmed and the waveform criteria for placement cannot be satisfied, the tube should be removed and the patient re-intubated. One final criterion to add to this is the SpO2. If the SpO2 deteriorates at any point before the ETCo2 waveform is restored, then this serves as further evidence that the tube is likely malpositioned and should be removed and replaced.
It is important to address a potential conundrum with re-intubation. We previously established the more times we attempt intubation, there is an increased risk of adverse events to include esophageal intubation. However, the risk of these adverse events pales in comparison to the mortality outcomes from patients with esophageal intubations. This is a risk in which we are forced to act to correct a malpositioned tube.
Removal and re-intubation should be our default approach. Perseverating and attempting to explain away a poor waveform (outside of the clinical context) are easy ways to fall victim to cognitive bias and potentially continue down a fatal pathway for the patient. The algorithm to avoid this eventuality follows a logical path of observing a poor waveform appearance; actively excluding the possibility of the tube being in the wrong place; and replacing the tube if found in the wrong place.
Conclusion
Esophageal intubations are widely considered a “never event” for the emergency airway management world. It is a known fatal complication of airway management and its discovery can be masked by various types of cognitive bias and poor mental models of tube confirmation.
Traditional methods of tube confirmation have been shown by the PUMA advisory group to be anything but and clinical assessment has fallen out of favor in tube placement confirmation.
The gold standard of qualitative waveform capnography in which the operators can observe both a number value and a waveform defeats the cognitive bias and poor mental models, but it is not without its own limitations and confounders. While being highly sensitive and specific to exhaled carbon dioxide, it can be rendered less reliable in certain clinical contexts and when the tube is placed above the vocal cords.
It is not enough to merely suspect that the endotracheal tube is in the wrong place, we have to actively exclude the possibility of esophageal placement by looking and confirming the exact location of the tip of the ET tube.
In some cases, it is safer to simply remove the tube and replace it again, but in other cases this is not a viable option. This highlights the need for training and education in contingency planning in airway management so that we can respond appropriately to these emergent events.
References
- Chrimes N, Higgs A, Hagberg CA, Baker PA, Cooper RM, Greif R, Kovacs G, Law JA, Marshall SD, Myatra SN, O’Sullivan EP, Rosenblatt WH, Ross CH, Sakles JC, Sorbello M, Cook TM. Preventing unrecognised oesophageal intubation: a consensus guideline from the Project for Universal Management of Airways and international airway societies. Anaesthesia. 2022 Dec;77(12):1395-1415. doi: 10.1111/anae.15817. Epub 2022 Aug 17. PMID: 35977431; PMCID: PMC9804892.
- Russotto V, Myatra SN, Laffey JG, Tassistro E, Antolini L, Bauer P, Lascarrou JB, Szuldrzynski K, Camporota L, Pelosi P, Sorbello M, Higgs A, Greif R, Putensen C, Agvald-Öhman C, Chalkias A, Bokums K, Brewster D, Rossi E, Fumagalli R, Pesenti A, Foti G, Bellani G; INTUBE Study Investigators. Intubation Practices and Adverse Peri-intubation Events in Critically Ill Patients From 29 Countries. JAMA. 2021 Mar 23;325(12):1164-1172. doi: 10.1001/jama.2021.1727. Erratum in: JAMA. 2021 Jun 22;325(24):2507. doi: 10.1001/jama.2021.9012. PMID: 33755076; PMCID: PMC7988368.
- Mort TC. Esophageal intubation with indirect clinical tests during emergency tracheal intubation: a report on patient morbidity. J Clin Anesth. 2005 Jun;17(4):255-62. doi: 10.1016/j.jclinane.2005.02.004. PMID: 15950848.
- Cook TM, Woodall N, Harper J, Benger J; Fourth National Audit Project . Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society, II: intensive care and emergency departments. Br J Anaesth. 2011;106(5):632-642. doi: 10.1093/bja/aer059
- Sackles, J. (2013). The Importance of First Pass Success When Performing Orotracheal Intubation in the Emergency Department. Acad Emerg. Med, 71-78.
- Sakles JC, Ross C, Kovacs G. Preventing unrecognized esophageal intubation in the emergency department. J Am Coll Emerg Physicians Open. 2023 Apr 29;4(3):e12951. doi: 10.1002/emp2.12951. Erratum in: J Am Coll Emerg Physicians Open. 2023 May 30;4(3):e12986. doi: 10.1002/emp2.12986. PMID: 37128296; PMCID: PMC10148380.
- Silvestri S, Ralls GA, Krauss B, Thundiyil J, Rothrock SG, Senn A, Carter E, Falk J. The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system. Ann Emerg Med. 2005 May;45(5):497-503. doi: 10.1016/j.annemergmed.2004.09.014. PMID: 15855946.
Cody Winniford is a flight paramedic and base manager in Baltimore, MD. He has a passion for sharing his professional experience in EMS and management. Cody’s clinical and leadership development background spans both military and civilian settings and has served in several capacities as a leader and prehospital clinician. He specializes in air medical and critical care transport, as well as organizational development and leadership development. He is an active speaker on various leadership and clinical topics and is an established and successful educator for prehospital clinicians of all levels. He has a passion for human performance improvement and the mental health and performance aspects of prehospital care.
