An EM Resident’s Guide to Basic Airway Management

Authors:

  • Justin Rice, MD
  • Sagar Desai, MD
  • Eunice Monge, MD
  • William Chiang, MD

Preface:

Airway management is one of the most critical skills in emergency medicine, yet it can be one of the most challenging to master. Residents often receive varying advice from different attendings, each with their own background and expertise, which can lead to confusion. The abundance of research, much of it contradictory, adds to the complexity. Our goal with this guide is to simplify the basics of airway management, from patient assessment and preparation to intubation and troubleshooting. While this guide isn’t exhaustive, it’s designed by residents, for residents, to provide practical tips and foundational knowledge that’s crucial in the fast-paced, high-stakes environment of the ED. Remember, practice and understanding are key to improving your skills, and staying updated with the latest research will help you continually refine your approach.

 

Section 1. Introduction

Airway management is a critical ED skill to master. Success at intubation likely takes more time and practice than other procedures, as shown in recent research on ED residents and their success rate at intubating, measured as a function of their total number of intubations (See Figure 1).

Figure 1: Cumulative success rate at intubation, modified from (Je, 2015)

The ACGME-defined minimum of 35 intubations to graduate would suggest a failure rate of 20%, or 1 out of every 5 intubations–this is obviously not an acceptable percentage for such a consequential procedure. Practice may not achieve perfection, but it will make you better.

In this review, we’ll discuss how to evaluate a patient’s airway, how to best position and preoxygenate the patient, how to take the airway, either by video laryngoscopy (VL), direct laryngoscopy (DL), or LMA, and how to confirm the location of the endotracheal tube (ETT) after it is placed. All of these topics are active areas of research, so keep an eye on the literature for new innovations!

Section 2: How to Evaluate the Airway

Just like with any ED procedure, before you start you’ll need to evaluate the patient, consider their unique anatomy and physiology, and consider the best approach to take. There two critical components to every airway evaluation include: 

  1. The person’s anatomy that will predict if the intubation will be difficult or not, and if so, how difficult. We’ll consider “difficult intubation” for our purposes here to mean an intubation that requires multiple attempts with DL or the use of a hyperangulated VL / advanced technique (e.g. fiber optic through the nose).
  2. The respiratory physiology and hemodynamics of the patient.

 

This document will focus on the anatomical considerations and aspiration risk.

  • History
    • When did they last eat (aspiration risk)?
    • Do they snore/have OSA (predictor of difficult intubation)?
    • Have they had surgery at this hospital before? (look them up in the EMR to see if they’ve been intubated before, and look at the note on the difficulty and grade of view.)
    • Have they ever had a tracheostomy or other throat/neck surgery? (This could suggest tracheal stenosis – a narrow section below the cords, and thus increased difficulty passing the tube)
  • Physical Exam
    • Dentures? (leave them in for BVM-ing, but remove prior to intubation)
    • Any loose teeth? (don’t knock them out). Buck teeth? (makes intubation more difficult). Broken / sharp / missing teeth? Missing incisors is bad for bagging, good for tubing. Missing molars on the right side can sometimes make scissoring the jaw a little tricky.
    • BMI is not a great predictor of difficult intubation (Moon 2019), however, more obese patients have shorter times to desaturation (Jense 1991), which can make these cases more challenging. Very obese patients with obesity hypoventilation syndrome may have almost no reserve at all, and start desaturating as soon as they stop breathing. Likewise smokers and asthmatics likely have lower times to desaturation.
    • How thick is their neck? You don’t need a tape measure for this, but thick=harder intubation, with diameter >43cm having a likelihood ratio of ~6 for a difficult tube (Gonzalez 2008)
    • Can they extend and flex their neck? If they can’t, they’ll likely be a difficult airway, because they cannot be placed in optimal (sniffing) positioning, to be discussed later.
    • Can they cover their entire top lip with their bottom incisors? This is called the Upper Lip Bite Test, which is basically a measure of how well you’ll be able to jaw thrust and/or open up their airway with a laryngoscope.

Upper Lip Bite Test

Figure 2: Demonstration of upper lip bite test: class 3 is very specific for difficult intubation!

Having a class 3 on the upper lip bite test is a strong predictor of a difficult intubation (Detsky 2019) – likelihood ratio of 14! This is very fast to perform, however, you will likely have to demonstrate what you want the patient to do.

 

The 3/3/2 rule:

Figure 3: how to perform the “3/3/2” rule (Image modified from UpToDate.com)

If the patient has less than the specified measurement of 3, 3, or 2 fingers in these parameters, this is very specific (95%) for having a more difficult intubation (Mahmoodpoor, 2013)–although only about 25% sensitive. 

 

Mallampati score – The most commonly used metric for screening for a difficult airway (also one of the fastest).

Figure 4: Demonstration of Mallampati classes. Remember, in the airway, lower is always better (Mallampati class, Cormack & Lehane grade, Upper lip bite test…)

If you see the tip of the uvula and the whole tonsillar pillars, that’s a class 1. Just the uvula but not the pillars, class 2. Can see the base of the uvula but not the tip, class 3. Not even the base of the uvula is class 4 (Having a class 3 or class 4 has about 85% sensitivity and 80% specificity for predicting a difficult intubation (Mahmoodpoor, 2013). Patients with ‘’Class 0” Mallampati comprise about 1% of the adult population, and are uniformly easy to intubate (Ezri 2001). Keep in mind patients with Down syndrome or other syndromic appearance often have anterior airways and are difficult to intubate.

 

This all sounds like a lot, but it all only takes a few moments, and the sum of these quick assessments has been shown to be more or less equivalent to an anesthesiologist’s judgment in detecting a difficult airway (Norskov 2016). For an unstable patient in the ED, you will definitely not be able to do this entire evaluation, but any part will be helpful – even if it’s just having them range their neck and thrust their jaw while getting pre-oxygenated, or looking in the mouth to make sure the jaw isn’t wired shut! You may glean some very useful information in just a moment that could greatly affect your intubation technique or preparation. You should practice this airway evaluation every time on your OR patients and ED procedural sedation patients.

That said, studies have shown something like 90% of difficult intubations are unanticipated (Norskov 2015) in spite of knowledge of these techniques, so it is best practice to prepare for every intubation as if it will be a difficult airway, including getting out and preloading all of your equipment, having a VL turned on and ready to go, and maximally pre-oxygenating the patient, as will be discussed in the next section.

Section 3: How to Preoxygenate

Physiology

First some important concepts. Don’t fall into the trap of assuming an SpO2 of 100% means the patient is fully pre-oxygenated. Pulse oximetry measures the percentage of capillary hemoglobin that is saturated with oxygen. This doesn’t necessarily mean that the patient is fully oxygenated, but that their capillary hemoglobin is saturated. Without proper preoxygenation, these patients’ upper and lower airways will be filled with room air (mostly nitrogen and only 21% oxygen!). If you paralyze a healthy person breathing RA, you may have only a few minutes before they desaturate to dangerous levels: 

Figure 5: Time to desaturation while apneic if NOT preoxygenated. (From Benumof 1997). Notice that once you hit about 90%, things go bad VERY FAST.

And the above graph is likely a best case scenario – (Drummond 1984) found that some otherwise seemingly healthy people breathing room air desaturated to the 70%’s within just 1 minute of induction of anesthesia! 

Why do children and sick people desaturate sooner than healthy adults?

  • Children have proportionally higher oxygen consumption compared to their FRC (Laycock 1988) (functional residual capacity – the amount of gas in your lungs after you passively exhale), while sick people also have higher oxygen consumption and probably some degree of acute lung injury, resulting in an increased A-a gradient and decreased FRC via atelectasis (Lumb 2005).

To avoid dangerous hypoxia, we want to replace the ~80% ambient nitrogen with oxygen (called “denitrogenation’’) and saturate their upper/lower airways as well as their venous blood with oxygen.

You’ll notice on your anesthesia rotation that some of the fancy OR ventilators can actually measure end-tidal oxygen. In healthy people breathing room air, this number is fairly low (we exhale mostly CO2!), but when pre-oxygenating a patient in the OR, you’ll often try to get the end-tidal oxygen concentration as high as 80%-90%! This provides an objective measurement of pre-oxygenation–but we often don’t have this luxury in the ER. While we can’t measure end-tidal oxygen objectively, just remember that patients need both the appropriate modality (nasal cannula, non-rebreather, high-flow nasal cannula, BiPAP) as well as time to appropriately pre-oxygenate/de-nitrogenate.

How long does pre-oxygenation take?

  • Studies on healthy volunteers breathing 100% oxygen demonstrate that 98% of the nitrogen is out of your lungs after 3 minutes, and correspondingly, the exhaled SpO2 also levels off (See Figure 6 below) after about 2-3 minutes. In an unhealthy person who’s not breathing so well, has some atelectasis…you may not get such good results.

Figure 6: Breathing 100% O2, experiments have shown that our % of exhaled nitrogen (an approximation of alveolar nitrogen) decreases to about 2% after 3 minutes (Carmichael 1989), while exhaled O2 levels increase up to about 90% and level off at the same time (Berry 1994) – this – exhaled fraction of oxygen- is what is measured on the anesthesia machines in the OR.

Figure 7: (modified from Tanoubi 2009). This graph shows the gaseous equivalent volume of oxygen stored in the lungs, bound to hemoglobin, and dissolved in the plasma for people breathing room air (far left) vs the same people pre-oxygenated by breathing 100% O2 (far right), and then after they have desatted to 90% while apneic (center) . 

As we can see in figure 7, we can get A LOT of extra oxygen in the body with pre-oxygenation, and considering that a healthy person at rest uses about 250ml of oxygen per minute (Tanoubi 2009), this explains why pre-oxygenated patients take longer to desaturate when they’re apneic than patients breathing room air. Certain conditions cause higher oxygen consumption, e.g. febrile +/- shivering patients (~25-40% higher (Manthous 1995) )) or patients in severe respiratory distress (up to 100% higher (Field 1982)), and those patients will likely burn through that reserve and become hypoxic even faster.

Also obvious in this graph is that most of the extra oxygen gained during this process is stored in the lungs, but there’s also a small amount of extra O2 added to the hemoglobin and dissolved in the plasma. The amount of extra oxygen we can store in the lungs is basically equal to the FRC, which depends on many things (see below).

Figure 8: (From Lohser 2011, originally from (Benumof 1995)) Shows how the FRC progressively decreases as you take an upright person and lay them down supine (decrease of ~25% (Ibenez 1982)), then again as you sedate them ( ~5%, (Prato 1983)), then again as you paralyze them. The situation can be much more severe in the obese, who may lose 50% of their FRC upon sedation/paralysis! (Damia 1988) which explains their precipitous desaturation in Figure 5.

 

How to optimally pre-oxygenate

What can you do to better pre-oxygenate a patient just prior to intubation? 

  • First of all, place a non-rebreather (NRB) AND a nasal cannula on the patient, and turn them up to full-blast oxygen. Not to the nurses’s 15L/min or 6L/min – full-blast! This is called “flush rate”–you can get flow rates (Driver 2017) of 50L/min or even more. Why does this help, and why do dyspneic people tolerate the nasal cannula and the non-rebreather better than just the non-rebreather alone? If hyperventilating, they may be pulling tidal volumes of 40L/min or more, and the 15L/min from the NRB is not enough oxygen – they’ll be breathing in a lot of their own expired air full of CO2, and you don’t want that (Levitan 2015). 
  • In obese patients, it was famously shown that you can do better by keeping people in ~25 degrees of reverse trendelenburg during pre-oxygenation, which leads to maybe 50 seconds of extra apneic time before the patient starts to become hypoxic (Dixon 2005). This also works in non-obese patients, where you may get 90 extra seconds before the patient desaturates (Ramkumar 2011). The thought is that when supine, the weight of the abdominal contents pushes up against the diaphragm, leading to reduced FRC, and thereby less reserve oxygen in the lungs. Sitting them up improves the FRC, and opens up the lungs. Having them sitting up at 30° is also better than supine, but not quite as good as reverse Trendelenberg (Boyce 2003).
  • Doing all of this and you’re still not getting them as well pre-oxygenated as you’d like? Turn the PEEP valve on your BVM up to 5, and give them O2 through the BVM with a tight seal on their face and the nasal cannula on full blast. This will help prevent atelectasis (Weingart 2012) likely by increasing the FRC. Want an even more powerful option? Pre-oxygenate with BiPAP (Farkas 2015). NIV was recently shown to be much superior in avoiding hypoxia during intubation, compared to using a NRB (Gibbs 2024).
  • What about once the patient is already apneic? Why not leave a nasal cannula blasting oxygen into their nose? This is called “apneic oxygenation” and it works fantastically to prolong the time before the patient desaturates, even though the patient isn’t breathing. (Ramachandran 2010) showed that doing apneic oxygenation increased the average time to desaturation in obese patients by more than 90 seconds! The thought being that as long as their airway is open, the oxygen will passively diffuse down into their lungs, as long as you keep it at 100% in their upper airway. 
  • As another option, if you have access (and the real estate), could you just put them on Hi-Flow-Nasal-Cannula (HFNC) delivering 30-70L/min of O2 through their nose? This sounds great in theory:
    • In patients who are at risk for vomiting, you can get them oxygen without covering their mouth (As you would with e.g. a BVM or BIPAP or an NRB). 
    • HFNC likely “washes-out” the CO2 from the upper airway, thus decreasing the physiological dead space (Delorme 2020) 
    • The HFNC humidifies and warms the air, making it much more comfortable and tolerable than the cold dry O2 coming directly from the wall.
    • HFNC also provides some PEEP (something like 0.8 mm Hg for each 10L/min of flow rate (Groves 2007) with about 2mm Hg extra for closing the mouth), which will help stent open collapsed alveoli. 
    • HFNC has been shown to decrease the work of breathing, increase the tidal volume, and decrease the respiratory rate (Vargas 2015), likely in part due to the added positive pressure mentioned above- so using it early may even help you avoid intubation!

In people with healthy lungs, it seems to work great – some patients on HFNC can (amazingly) be apneic for 10’s of minutes without desatting! (Patel 2015). However, in critically ill patients the results are more mixed, with some studies (e.g. Miguel-Montanes 2015) showing superiority over NRB for preoxygenation, while others (e.g. Vourc’h 2015) do not. So the actual benefit for most ED patients is unclear. Also beware, there were studies claiming that HFNC somehow “washes out” the CO2 from the alveoli during apnea, alleviating the descent into acidemia in apneic patients (Patel 2015), but these were plagued by inaccurate measurement modalities, poor experimental design, and questionable logic, (see Toner 2020 for a review).

  • This is more of an oxygen-use issue than a  pre-oxygenation issue, but it’s something to think about when considering the risk of hypoxia in your patient: When succinylcholine makes the patient fasciculate all their muscles, they actually use up some oxygen, so a patient who gets succinylcholine will desaturate before they would if they’d gotten rocuronium. How much? Almost 40 seconds sooner! (Tang 2011). That’s a long time during a difficult intubation.

 

But what if you don’t know their oxygen level?

In the OR, the patients are usually warm and well perfused, and you can get a good capillary SpO2 sat from their fingers without any trouble …but in the ED sometimes your patient may come in hypothermic, or in shock and poorly perfusing their extremities, and their fingers may not be getting good blood flow. This can be a very dangerous situation, because if you try to intubate them while their oxygen level is already very low, they could easily arrest during the process. Even if they’re well oxygenated, a bad SpO2 signal on the monitor will be distracting everyone in the room. So this is important, and there are a few issues to discuss.

First of all, just because the monitor lists a decent O2 % doesn’t mean that it’s real. Only trust the number if it has a good waveform, and the person is sitting still and not wiggling their finger. See below for two examples where the monitor reads in the 80s while the sticker is not even attached to a person.

Figure 9: Left: O2 sat sticker is hanging off the monitor handle, attached to nothing, but monitor reads 82%, and you might convince yourself you see a tachycardic waveform. Right: O2 sat sticker reading off a box of gloves, shaking a little to make a convincing waveform and reads 85%.

If the O2 sensor is attached to someone’s finger, and they’re still, but you’re not getting a good waveform, there are a few things you can try to troubleshoot the situation:

  • If they have opaque nail polish on, try putting the sensor on sideways, shooting the light laterally through the finger (it should still read if their finger is well perfused). See figure 10. Some nail polish will totally block your oxygen sensor from reading, other nail polish may give you a falsely low % (Cote 1988), so you should be doing this on everyone with fancy nails.
  • If they’re cold, you could put a hot pack in their hand, or fill a rubber glove with hot water and put that in their hand, interlocking the glove fingers with their fingers (Zeiden 2012) – this helps vasodilate the finger and gets you a better signal, although it may take several minutes, and you may not have that long with a critically ill patient.
  • If that doesn’t work, research has shown that doing a lidocaine digital block of one of their fingers will vasodilate and warm the finger, and can get you a better signal (Bourke 1991). The idea is that if you block the digital nerves, you’re blocking the sympathetic vasoconstriction as well. Note that this will also require time that you may not have.
  • Some authors have noted that rubbing a bit of nitroglycerin paste on the sensor location can help with local vasodilation, and hence improve your pulse oximeter signal (Alexander 1989), but we have never done this, and would advise great caution before giving a vasodilator to someone in shock.
  • Put the finger pulse ox on the ear! See figure 10. Sometimes earlobes are better perfused than fingers, sometimes they are not. No matter what, it’s very hard to get the sticker to stay put, especially if the patient is moving around. Other locations, such as the lip and the tongue can be more challenging…

Figure 10: Upper left: Turning the pulse ox sideways can help with nail polish. Upper right: earlobes can sometimes give a reliable signal when the fingers are poorly perfused. (Thanks Dr. Tom Sullivan for modeling) Lower left and right: lips and tongues (dog photo from Mair 2020) can also be used, but are logistically challenging.

Perhaps the best option is the nasal alar sensor (see Figure 11). The nasal alae are perfused by an anastomosis of both the internal and external carotid arteries (Morey 2014), and continue to get good blood flow even in most people in shock who have poorly perfused fingers (Schallom 2018). Unfortunately, many EDs are not equipped with these.

Figure 11: Nasal alar pulse ox sensors have been shown to work better in patients with poor perfusion (Photo from Philips.com)

And then there’s the old put-the-finger-sensor-on-the-forehead trick. Does it give you a reading? Yes it often does. Is it accurate? No one knows. The idea is good: the forehead has limited ability to vasoconstrict compared to the fingers, and there are specially designed reflection oximeters made for the forehead for use in poorly perfused patients. The problem is that the finger pulse oximeter sensors purchased by most hospitals are transmission oximeters, not reflection oximeters (See figure 12). 

Figure 12: Transmission vs reflectance pulse oximetry (photo from (Aithal 2015))

The math used in the signal processing of each is different, and using a transmission oximeter as a reflection oximeter has been shown to sometimes be unreliable in terms of getting an accurate estimate of the oxygen saturation (Smithline 2010). Seemingly only one paper has ever been written on this subject, so we don’t know much about how inaccurate the measurements are, or when they might be valid. However, until we get nasal alae sensors at all hospitals, sometimes this is your only way to get any kind of estimate of the oxygen saturation at all, so check out figure 13 for some tips on how to use them.

Figure 13: Covidien sensors (above) will often work straight out of the package. Masimo sensors (below) are made such that the light and the sensor are too far away, so you may not be able to get a signal at all without crimping the sensor a bit to move them closer together.

 

And there’s yet another issue: even if you have a warm well perfused finger which is not trembling or wiggling, the SpO2 you measure might be inaccurate. (Feiner 2007) suggests that most adhesive pulse oximeters likely have a positive bias in hypoxic dark skinned patients, some of up to 10%. So for example, a Black person with a true hemoglobin saturation of 60% might have a pulse ox falsely reading 70%, a potentially very dangerous situation. Very little research has been done in this area, but be skeptical when your O2 sat looks better than your patient, especially if they have darker skin tone. 

Sound complicated and difficult? When in doubt, if you are making critical decisions and need to know the oxygen saturation: get an ABG.

Section 4: How to Position the Patient

What’s the worst position to intubate a patient? Probably the position they arrived in. First, the obvious: move the head of the bed away from the wall so you have adequate space. Pump up the bed to a height at which you think it will be comfortable to intubate. Studies show (Lee 2014) that most people are the most comfortable with the bed pretty high – with the mouth of the patient in line with your xiphoid process. 

Now how about all of this pillow / sniffing / ramping business? It’s easy to forget about this in an emergency, but it can make a huge difference in your intubation success. If the patient is lying on their back in a neutral position and you open their mouth, you probably won’t see their cords – because their mouth is not aligned with their pharynx / larynx. However, lifting the head and extending it back a little bit puts them in the “sniffing position”, where you should be able to get a better view.

Figure 14: A shows neutral position – everything out of line. B shows the head lifted towards sniffing position, C shows additional extension of the neck (taken from Whitten 1989). Most sources say the meatus of the ear should be at the elevation of the sternal notch (Collins 2004) to make it the sniffing position, although the ear is shown lower in this picture.

In some patients, you may need to start jamming folded sheets and blankets and things under the upper back to make a “ramp’’ to align the ear with the sternal notch. If the patient is really anterior and you can’t see the cords in the sniffing position, sometimes you can get a better view by lifting the head even higher, as shown in Figure 15.

Figure 15: LEFT: patient lying supine – meatus of ear is definitely below level of the sternum – you may have a difficult time getting a good view in this position. But note the excellent opportunity for IV access in the EJ. CENTER: patient ramped, with meatus at level of sternal notch – a good position to start for intubation. RIGHT: if you find yourself failing to get a good view of the airway, and wishing that you had ramped the patient, you can also try “dynamically” lifting the head with your R hand to get a better view, after which you can ask a helper to hold the head in that position (Schmitt 2002).

Interestingly, in addition to getting better pre-oxygenation (as discussed in part 3 of this guide), putting your patient in some reverse Trendelenberg position may be helpful with getting a better view once the blade is in. In (Lee 2007) they showed a clinically significant improvement in view just by putting the patient in 25 degrees of reverse T-berg. The reasoning for this is unclear, but something to consider!

Section 5: How to Perform Direct Laryngoscopy

Now you’ve pre-oxygenated and positioned your patient, you’re ready to intubate, and you want to use DL. In this section we will try to address all the little decisions you need to make, and cover what to do when you initially can’t get a view.

  1. A) Choose a laryngoscope blade. We will only talk about Macintosh blades. So the question is: Mac 3 or 4? You will likely hear the following things, depending on who you ask:
  • “Tall people: Mac 4. Short people: Mac 3”
  • “Men: Mac 4. Women : Mac 3”
  • “Short (Mac 3) vs long (Mac 4) based on thyromental +hyoid-mental distances”
  • “I always use a Mac 4 – if the airway is short, I just don’t insert it so far”
  • “I always use a Mac 3 because that’s what I learned on. If I can’t reach the vallecula, I pull out and switch blades.”

People have very strong feelings about their own personal rules, but there is no great research in this area. The only randomized controlled data available shows that for new interns intubating mannikins (so take this with a tablespoon of salt), successful intubation rates and speed of intubation are both better with mac 3 than mac 4 (Kim 2018). 

B) Fix your posture Traditional teaching is that you should stand with a straight back, with your face back away from the person’s mouth, not hunched over. Your left elbow should be close by your side for support. You should hold the laryngoscope blade down near the hinge, not up high. 

There are not a lot of studies on this, and best practice is evolving. A number of observational studies (Matthews 1998) (Walker 2002) have shown that very experienced intubators (with many hundreds of DLs) do tend to stand further back than novices, with their arms more straight. 

Figure 16 Left: (from Roberts and Hedges, 2014) Traditional instruction was to put the bed super high, keep a rigid right arm, mislabel it as the left arm, and tie down your patient. Now that we sedate and paralyze our patients prior to intubation, the restraints are generally no longer necessary. The straight arms also likely made intubation challenging. Center: another example of poor posture for intubation, very common in novice intubators  – the resident’s face is too close to the patient, he’s also hunched over because the bed is too low, and his left arm is chicken-winged out, instead of close to his side. Right: Improved posture, probably after some remediation – straight back, mouth of patient at level of xiphoid process, left arm in next to thorax. 

It’s also thought that while intubating, the left elbow should be held close to the body, for better ergodynamics. However, other traditional best practices (e.g. must keep arms rigidly straight as in Figure 16 Left) are being discarded. Levitan showed that almost no one is far back enough to have binocular vision during laryngoscopy – it’s always monocular (Levitan 1998). It was also shown that usually if you’re right handed, you automatically visualize the larynx with your right eye (~95%). Left handed people also tend to use their right eye, but a large minority (about 20%) use their left eye instead.

Other studies have shown that experienced intubators hold the laryngoscope differently (Zamora 2014), with their hands closer to the hinge of the laryngoscope. It is not proven that this leads to more intubation success, but it is what the experts do.

 

                       

Novices tend to grip like this: the wrist is more supinated, and the handle is held farther away from the blade. 

Experts tend to grip like this: less supinated, and closer to the blade, with the back part of the blade abutting the hypothenar eminence.

Figure 17 Observational findings from (Zamora 2014) on how to grip the blade

C) Scissor the mouth open. Put your thumb on the right canine (or further back on R lower molars), and your middle finger on the upper right molars, and scissor your fingers so as to open the mouth as wide as you can. See figure 18 below. Try to get your fingers / hand as deep in there and as far to the right as you can, to open the mouth as much as possible and to leave lots of room to put in your blade on the right side. Most people seem to get better leverage using their middle finger than their index finger.

 

             

Figure 18: LEFT: use thumb and middle finger as shown to open the mouth. RIGHT: Try to get as deep and as far to the right as possible, to give yourself lots of room for putting in the blade.

 

D.  Insert blade Now that the mouth is REALLY open, you can slowly and carefully insert the tip of your blade between the tongue and the R lower molars / R mandible, and start to sneak it back in there posteriorly, separating the tongue from the R side of the mouth. If you couldn’t before, you should start to get a view of the palatine arches and the uvula. This is reassuring as the uvula points towards the epiglottis (See figure 19)

E.  Sweep tongue to left While you’re doing this, and slowly inserting your blade further, you should also be moving the whole blade and handle leftwards, towards the midline, to sweep the tongue to the left, and out of your way. This should start to bring the epiglottis into view:

Figure 19: LEFT: inserting the blade between the tongue and the molars/mandible, and as RIGHT: you get deeper, sweep the tongue to the left to get it out of the way, and expose the epiglottis

Warning: DO NOT just insert the blade directly over and on top of the tongue, and try to intubate like this. Human tongues are muscular, incompressible, and floppy. You cannot intubate over them with a standard geometry blade and expect them to squash down to give you a good view. They won’t do it. Mannikins have air-filled compressible tongues that are fixed in place, and you can intubate over the tongue on them, which teaches terrible technique, so beware.

While you are inserting the blade and proceeding deeper, call out what you are seeing to your attending, so they don’t get nervous and hover over your shoulder, or worse, take your tube. In order, the landmarks you should see are: palate, uvula, posterior oropharynx, collapsed esophagus (maybe), epiglottis (if hanging down), or arytenoid notch, and cords.

F.   Go deeper, and put the tip of the blade in the vallecula:

Once you see epiglottis, you can infer where the vallecula is. Get a better view by sliding the tip of the blade of your laryngoscope into the vallecula. When you do this, the tip of your laryngoscope will press on a structure called the hyoepiglottic ligament. See figures 20 and 21.

Figure 20: Sagittal view showing some important airway landmarks – note the structure labeled 29 – the hyoepiglottic ligament. Pressing on this structure, which connects the hyoid bone (which acts as an anchor) to the epiglottis(28), causes the epiglottis to swing anteriorly, giving you a better view.

The hyoepiglottic ligament is also called the “median glossoepiglottic fold” AKA the “midline vallecular fold”. Pressing on it with your blade has been shown to be associated with better views (Driver 2021). See figure 15A to see how pressing on this ligament with the tip of the blade can move the epiglottis out of your line of sight, both in a transverse view (of a manikin), and a sagittal view (of a cadaver).

Figure 21: Showing how pressure on the hyoepiglottic ligament gives a good view (cadaver views adapted from Driver 2021)

 

You may or may not have a view at this point. Hopefully the above techniques have served you well, but the epiglottis still may be obscuring the cords partially or entirely. Even if you do have a view, as in figure 22, you may not have room to pass a tube while maintaining this view. See figure 25 for how this can go wrong.

Figure: 22: typical view when the blade is in the vallecula, pressing on the hyo-epiglottic ligament, and popping up the epiglottis. You can see the arytenoid notch and the bottom of the cords, but you may not have a lot of room to pass the tube.

At this point, you should “lift”, to open up the airway and get a better view. But the way that you lift is very important. You should exert force “towards the opposite upper corner of the room” i.e. in the direction of the laryngoscope handle. You should NOT torque the blade up and back, AKA “rock” the laryngoscope on the teeth, which tends to put too much force on the patient’s incisors (and break them – the #1 cause of lawsuits against anesthesiologists is dental trauma!). See figure 23. This should improve your view.

Figure 23: lift towards the point where the opposite wall meets the ceiling. Do not rock back and break the incisors.

How hard do you lift? (Hastings 1996) showed that the force required to get a good view, even on patients with low Mallampati scores, could be routinely up to 9-13lbs, but also that this force required varied widely among anesthesiologists, even on the same patient, indicating that subtle changes in technique likely make a big difference. Ever wonder how hard you would need to lift to break the blade? You’re not alone–(Choi 2021) tested plastic disposable video laryngoscope covers (like we use on the glidescopes) and found that most will start to irreversibly deform or break at around 30-40lbs of lifting force. If you’re lifting this hard, especially with a VL, you’re likely doing something very wrong (especially since the average human head and neck only weighs about 10lbs altogether (Yoganandan 2009)). 

Traditionally, view has been scored on the “Cormack & Lehane grade”, where grade 1 is a view of the entire glottic opening opening from the anterior commissure to the arytenoid notch, grade 2 is a partial view of the glottic opening, grade 3 is a view of the epiglottis but no view of the cords, and grade 4 is no view of the epiglottis (see figure 24 below). Intubating someone with a grade 3 or 4 view is extremely difficult. If you have a grade 3 or 4, you should announce it and try to reposition or utilize a special maneuver (discussed below) to try to improve the view. If you can’t get at least a grade 2 view, pull out and start bagging the patient so that someone else or some other technique can be used to intubate this person. In (Yentis 1998) it was found that ~1% of (ob-gyn) patients had grade 3, and even less had grade 4, so this is a rare occurrence, but that these cases had a high likelihood of first pass failure even by highly experienced anesthesiologists.

Figure 24: Cormack & Lehane grades vs POGO scores. Cormack & Lehane are more old fashioned and more widely known, but POGO is more useful when talking about grade 2 views.

More recently, the POGO (“Percentage of Glottic opening”) score has been advanced as a more precise ranking system for Grade 1-2 views, and has been found to have less inter-rater variability than the Cormack-Lehane grading system (Ochroch 1999). As you can see in figure 24, there is a big difference between a POGO score of 70% vs a view with 5%, but these would both be rated as Cormack & Lehane 2. 

To the first time intubator, it may not be immediately obvious why a POGO score of 100% is better than a POGO score of 80% or even a score of 50% – it would seem that the glottis is easily identifiable, and you should be able to put a tube in there. The reason for striving for the best view possible is that everything gets more difficult to see when you actually try to pass the tube, as shown in figure 25.

Figure 25.  LEFT: A decent view of the epiglottis, and deep and posteriorly to the right, the cords, with a POGO of about 50% . RIGHT: view totally obscured by the ETT

And this is how esophageal intubations happen – you seem to have an OK view, but then as you are trying to pass the tube you temporarily lose your view, the anatomy shifts under the pressure of the tube touching it, and the tube goes in the wrong place – often sliding underneath the arytenoids and into the esophagus. 

Figure 26. It is easy for the tube to obscure your view, and for the tip to go down the esophagus.

Remember – your view of the airway is just a 2-dimensional view of a 3 dimensional structure – the arytenoids and the epiglottis look like they are equally deep to you, but they are not.

Figure 27. LEFT: Blue ray is your line of site – in which the epiglottis, trachea, and arytenoid cartilage all look like they are equally deep, as shown in Middle (from Gray, 1918). On the Right is a more detailed lateral visualization of the same airway, showing how much more deep the arytenoids are compared to the tip of the epiglottis

G.  Special Maneuvers to get a better view

If your best view using the above techniques is still not as reassuring as you’d like, there are some things you can do to improve it.

The BURP (Backward, Upward, Rightward Pressure) maneuver is a special thing that your assistant (attending) can do to get you a better view. It involves displacing the thyroid cartilage posteriorly until mild resistance is met, then superiorly about 2cm, then about 1-2cm to the patient’s right. It is performed for the purpose of getting a better view of the cords (i.e. a better Cormack-Lehane grade). In (Takahata 1998), patients with grade 2, 3, or 4 views who got the BURP maneuver, had significant improvements in views. 

One way to conceptualize this maneuver is to think about the vector force that your left hand is performing with the blade, and then having an assistant (or yourself with your right hand, as discussed below) push the thyroid cartilage the opposite direction to help bring the glottis into view.

Figure 28. Assistant performing BURP maneuver to hopefully get a better view for the intubator (Oh 2021)

An innovation and improvement on this technique is  “Bimanual Laryngoscopy” which is basically when you BURP the patient with your right hand, and then once you find the best position, your assistant takes over to hold the thyroid in position while you pass the tube. Alternatively, you can have your assistant put their hand on the thyroid cartilage first, and then use your hand to put them in the right position, as shown in figure 29:

Figure 29. Bimanual Laryngoscopy: positioning assistant’s hand to get the best view

Bimanual laryngoscopy was shown in (Levitan 2002) to be good for novice intubators to improve their POGO scores, and (Levitan 2006) to be far superior to BURP or no manipulation in terms of getting good POGO views.

The Sellick maneuver  AKA “Cricoid Pressure” on the other hand, is NOT done to improve the view. This is when someone puts pressure on the cricoid cartilage, pushing directly posterior, with the intent of occluding the esophagus. This is done when the patient has a full stomach and you are concerned that they may vomit, aspirate, and die. It is also done when the patient is very pregnant or very obese, and thus also at a high risk of vomiting (and aspirating and dying). It has been controversial for a number of reasons, including that there is no good data to support the technique, that for many people the esophagus is not directly behind the trachea, and that this maneuver actually makes intubation harder. See (Ovassapian 2009) for a good review. However, it is still routinely performed, because vomiting carries such a high risk of bad outcome. Note that both the British Difficult Airway Society and the All India Difficult Airway Society algorithms in the appendix both still recommend using cricoid pressure as a default on first attempts.

If you and/or your attending want to do the Sellick maneuver to try to decrease the chances of vomiting into the airway, that’s fine. But be aware that the Sellick maneuver and the BURP maneuver are two totally different things, and that there’s a lot of confusion out there. You might hear someone ask for “cricoid pressure” when what they really want is BURP because they can’t get a good view.

H.  Actually passing the tube

OK so you’ve positioned the patient, preoxygenated, sedated and paralyzed, put in your blade and got an adequate view, and now you’re ready to finally pass the tube! 

Use a stylet

Obviously, right? There is lots of good data that shows that first pass success is better with using a ETT with a stylet instead of an empty ETT (see e.g. Jaber 2021). And although there are very rare bad stylet-associated complications like tracheal perforation, these are thought to be exceedingly unusual and mainly a function of bad technique. Nonetheless there are people out there who like to use an empty ETT to intubate, such as some very old fashioned anesthesia attendings, and perhaps NICU attendings who specialize in intubating neonates, and seemingly also the French (Martin 2020). While you should always use a stylet or a bougie, it’s good to know that there may still be people out there who don’t.

Bend the stylet 

Unless you’re a lunatic who likes surprises during critical care procedures, you should bend your own stylet. In the olden days, supposedly people intubated with the stylet in the same shape as the natural bend of the ETT, called the “arcuate” bend. I have never seen anyone actually do this, and couldn’t find any studies even talking about it. Modern intubators seem to use the ‘’straight to cuff’’ bend shape, as shown below

Figure 30. Left: Straight to cuff vs arcuate, and Right: different angles of straight-to-cuff bends (Levitan 2006) 

And it’s thought that this shape allows better maneuverability once you’re down near the cords. How much should you bend your ETT? (Levitan 2006) analyzed this, and found that of a variety of angles between 25 and 60 degrees, the very shallow bends of 25-35 degrees seemed to have the best first pass success rate. Look at figure 30 on the right, and notice that this is a VERY shallow bend. Notice also that all ETTs are inserted onto the stylets so that the bevel faces the left. This is a good idea, and can facilitate better passage of the tube if you get hung up on cricoid cartilage ring, and can just rotate the ETT to the right to better insert it.

Anything else to be won by bending your stylet differently? Intriguingly, a new study (Wakabayashi 2021) looked at whether bending the ETT all the way up where the right hand holds it could help (see figure 31) by making the wrist and hand position more ergonomic.

Figure 31. Adding an extra bend (photo from Wakabayashi 2021) to make the ETT more ergonomic?

Seemingly it did. Intubation with the extra bend was about 20% faster, subjectively rated as easier by the intubator, and required less wrist and upper movement during the procedure. This idea is still pretty new, and we have not tried it, but it seems interesting.

ETT Size

There don’t seem to really be any RTCs studying this, but the authorities generally agree that a smaller ETT is likely easier to pass (Ferk 2015). And a small airway is always better than no airway at all. That doesn’t make a 6.0 the right tube for every job though, and we usually use 7.0 or 7.5s – See appendix for a more detailed discussion of ETT size selection.

Lube the ETT

Lubricating the cuff of the ETT has been shown to make a better seal with the trachea, decreasing microaspirations (Blunt 2001), and perhaps even decreasing post-extubation sore throats (anesthesiologists are crazy about decreasing post-op sore throats from the tube. They’ve tried local anesthetics, topical steroids, licorice, and even ketamine gargles! (Singh 2020)). Many ED and anesthesia docs also believe that lubing the end of the tube can make it easier to pass through the cords, and avoid getting hung up on the cricoid ring or the epiglottis. Remarkably, no one seems to have actually done a study on this.

Insert the ETT from far to the right

Most people advocate holding the ETT with a pencil grip, and hugging the right side of the airway as much as possible, to keep the tube out of your line-of-site to the glottis. (e.g. Roberts and Hedges 2014)

Figure 32. Correct position for insertion of the tube. Insert from the far right 

Where should you pick up the ETT? You can grab it at the location that you want the ETT to be at the teeth (e.g. for a male you might decide to insert to 24cm at the teeth). This way you don’t have to let go of the ETT while inserting to adjust your grip.

Pull down the cheek

Had a great view while you were scissoring and putting in the blade, but lost it as soon as you put the ETT in the mouth? Have a friend pull down the angle of the R cheek to give you some more space to hold and insert your ETT more laterally, out of your line-of-site, as shown in figure 33.

Figure 33. An assistant can pull down the cheek with an index finger while you put in the tube – in a narrow airway, every centimeter matters.

This is a very old and well-trusted method without a lot of actual studies done about it, but recently has been shown to decrease time to intubate, and subjectively decrease difficulty of intubation in children (Amir 2012).

The bougie

Sometimes, in spite of your best intentions, careful technique, skillful manipulations, and all the lube in the world, you can’t get the damned tube through the cords. Maybe the tube is too big and keeps getting caught on the arytenoids, or the epiglottis is flopped down a little bit, giving you a grade 2 view and preventing the tube from going where it is supposed to. If only there were something with a smaller diameter, with a smooth tip that wouldn’t catch on things, and helpfully up-turned at the end to sneak through the cords…fortunately there is, and it’s called a bougie. The bougies we have in the ED have coude tips (bent), which is what you want, and look something like what is shown in figure 34:

Figure 34: bougie with a coude tip

The idea is that you pass this through the cords, then hold it in place and pass the ETT over it (lubricate the bougie so that this goes easily), thus “railroading’’ the ETT into the trachea. 

In a randomized controlled trial (Driver 2018) showed that in patients who look like they will have a difficult airway, starting with the bougie improved first pass success rate to 96% (compared to 82% with the ETT+stylet) – a very impressive effect! Of note, this study was done at an institution where bougie-first intubation is routinely taught and practiced.

A seemingly smart thing to do is ‘’pre-load” the ETT onto the bougie (already lubed) to save time when getting the ETT over the bougie and through the cords, although in studies there doesn’t seem to be any measurable advantage in first pass success rate or time to intubation with preloading (Baker 2015). A definite disadvantage of this is that it makes your bougie heavier and more unwieldy, the ETT may make it harder to pass the bougie, and you may find the ETT flopping around in your face while you’re trying to intubate. An idea to avoid this is to load it with ‘’the kiwi grip” as shown on the right in figure 35, although this may make it harder to pass the bougie since the ETT is very close to the coude tip and will take up more room in the airway, and has not been formally studied for success rates.

Figure 35 LEFT: intubating with a naked bougie. CENTER: preloading the ETT onto the bougie – can be awkward, and decreases dexterity and fine motor skills with passing the bougie through the cords. RIGHT: “kiwi grip” may help with this? 

There are a couple of ways that you can still get hung-up, in spite of using the bougie:

  • You get the bougie in, and start to railroad the ETT over it, but the ETT lip gets caught on the arytenoids. Rotate the ETT 90 degrees to the left to put the bevel down–see below.

Figure 36: if the ETT gets caught on the arytenoids, you can rotate it 90 degrees counterclockwise such that the bevel slides over.

  • You get the bougie in, and get the tip of your ETT through the cords, but then can’t pass it further, because the tip of your ETT is hitting the cricoid ring – rotate the ETT 90 degrees clockwise to put the bevel up–see below.

Figure 37. Rotate the tube clockwise 90 degrees if caught on the cricoid or tracheal rings (from Levitan 2015), so the bevel will slide past.

To summarize–if you’re having trouble getting past the arytenoids, try rotating counterclockwise to put the bevel down. If you get past the arytenoids but have trouble getting past the cricoid rings, rotate clockwise to put the bevel up.

Section 7: How to Perform Video Laryngoscopy 

Using a hyperangulated VL can be a life-saver, particularly for patients with anterior airways, poor Mallampati scores, poor mobility, and those wearing c-collars. In principle, this sounds easy. The hardest thing about DL is getting a good view, and getting a good view is easy with VL! Unfortunately, after you get a good view, it can still be difficult to pass the tube, especially with a hyperangulated blade, so we’ll talk about some special techniques for overcoming common pitfalls here. 

First of all, why is it so much harder to pass the tube? A major factor is the shape and contour of the hyperangulated VL blade itself. Take a look at the shape of a mac DL blade:

Figure 38: A standard DL blade – very svelte! 

Notice that the flange is pretty wide, but that the little light doesn’t take up much room when you’re looking down the length of the blade, as you would be when intubating. 

Now compare this with the contour and shape of the hyperangulated VL’s. Here is the Glide scope cover aka the “Glidescope GVL® 3 stat”:

Figure 39: The hyperangulated camera cover for the glidescope – very chunky!

Notice that the square area where the camera fits takes up more room under the flange! This can get in the way of your ETT and make it hard to maneuver. What about the black glidescope disposables? This model is called “LoPro” because supposedly the camera has a lower profile:

Figure 40: The disposable “lo-pro” blades are better, but still chunkier than the old DL. The camera and light area takes up a little bit less room, but still much more than with the DL! It can still get in your way of inserting the ETT. 

Figure 41: Check out the amount of space to insert and maneuver the ETT using the DL mac 3 vs the glidescope covered camera. This may not seem significant, but when trying to make small adjustments on the ETT to get the tip through the cords, several mm can make a huge difference.

And this is why the first rule of VL is that you should always have a DL setup for backup. It is true, someone finally did an RTC on ICU level patients and found that first pass success IS better with VL than DL (Prekker 2023), but the fact remains that sometimes VL fails. In a study of ~500 attempted ED intubations (Mosier 2013), 15 patients were unable to be intubated with VL (That’s 3%!). DL was used to rescue-intubate 12 of these. The other three got cricothyrotomies.

Now to the specifics of the technique:

1) Scissor the mouth just like with DL, and look inside. If there is blood, vomit, or too much spit, put your suction in there and clean it up! You don’t want your camera to get covered with this stuff. If the tongue looks as dry as the Sahara – put some lube on the side of your blade that interfaces with the tongue – the glidescope blades are very sticky, and will stick to a dry tongue, preventing you from getting your blade properly positioned. 

Now insert the right aspect of the tip of the blade at about midline, going OVER the tongue (do NOT try to sweep the tongue to the side).

Figure 42: insert your blade directly on top of the tongue, in the center of the mouth or maybe a smidgen to the left of center (as suggested in (Cho 2008)) to give yourself more room to insert the ETT, as shown on right. Don’t try to sweep the tongue as you would in DL. 

2) As soon as you lose sight of the tip of the blade, STOP. 

3) Look up at the screen, and then proceed slowly, looking for anatomical landmarks as you go (see previous section). You should take caution to avoid going in too far with the blade, and perhaps putting the camera all the way into the esophagus. 

4) Once you visualize the arytenoids, and think that the tip of the blade is in the vallecula, you should stop, and lift towards the opposite wall/ceiling (just like in DL) and try to get a good view of the cords. If you’re having a hard time getting a sufficient view, having a helper jaw-thrust the patient seems to help (Corda 2012).  Do NOT get too close to the cords, or go over the epiglottis with the scope, because this will cause two problems:

  1. Your scope will physically take up too much room in the area you want to maneuver your tube, and it will block your ETT from being able to get through. 
  2. By inserting the hyperangulated blade very deeply, the angulation of the blade can actually push the airway more anteriorly, so then it makes such a sharp angle that you cannot pass your ETT through it. See figure 43, modified from (Levitan 2015) for visualization:

Figure 43: Putting the hyperangulated blade in too far can distort the airway, pushing it more anteriorly than your styleted tube can reach. Modified from (Levitan 2015). 

How can you tell if you’re too close? 

  • Your POGO (percent of the glottic opening that you can see) score should NOT be anywhere near 100% (Gu 2016)–if it is, you’re too close.
  • You should NOT see the cricoid ring on the anterior side of the trachea – this is called the Kovacs sign, (Levitan 2015)–if you see it, you’re too close.

If you are too close, just back up a little bit:

Figure 44 Left: showing the view from getting too close with the camera with positive Kovacs sign and 100% POGO score, and on the RIGHT: better positioning shown after backing up, with POGO about 50%, and the glottis in the top half of the screen, so we will be able to see the tip of the ETT come towards it. 

5) Now, holding your left hand still, grab your ETT by the most proximal part – do not use a pencil grip (see figure 45)–this will give you more leverage. Look at the mouth as you put the ETT in. When you lose sight of the tip STOP.

6) Now look back up at your screen, and start to gently maneuver your ETT towards the view on the screen. Once you get the tip through, you may find it difficult to pass the tube completely through the cords with the stylet in place, due to its geometry. Have a helper ‘’pop’’ the stylet out about 3 cm. You can also do this yourself with your thumb. (see figure 45 for how to do this) Popping the stylet should move the end of your ETT over the end of your stylet, straightening it out, and making it easier to push through the cords.

7) Once you’re through the cords, hold the ETT with a death grip, and have an assistant pull the stylet out towards the patient’s feet, as shown below (if you try to pull it towards the ceiling, it won’t come out. (See figure 45). BE CAREFUL: Keep your blade in place if possible while the stylet is pulled out – it can be difficult to pull out, and it would be easy for your helper to pull too hard and accidentally displace your tube from the airway with too forceful tugging.

Figure 45: 1): Hold the rigid stylet/ETT at the top as recommended in (Bacon 2015), not with a pencil grip as you would with DL 2) From this position, it’s easy to use your thumb to “pop” the stylet out when you get the tip of the ETT through the cords, which will also serve to push the ETT farther down the larynx. 3) To pull the rigid stylet the rest of the way out of the ETT, you’ll need to pull it forward, and then 4) down. Note that this is very different than with the bendable stylet, which you can just pull straight out. If you try to pull the rigid stylet up and out vertically, you’re at risk for extubating the patient or causing laryngeal trauma.

Having trouble getting the tube through the cords? This is a common complaint, and people have come up with all kinds of other things you can try. Taking out the ETT, leaving in the blade, and just trying to intubate with a bougie, then ‘’railroad’’ an ETT over it seems like the most obvious (Sharma 2011). However, other studies have shown that first pass success may be lower with a bougie than with a hyperangulated stylet when using a hyperangulated blade (Tosh 2018), as the geometry of the bougie is not designed for use with hyperangulated blades.

(Dupanovic 2006) recommends inserting the stylet and ETT together rotated 90 degrees to the right, like a ‘’gear shift’’. What about if you get your tube just through the cords, but it’s pointed anteriorly, ramming into the cricoid ring? Try rotating it to the right, so the bevel flattens out (Levitan 2011). You can also try putting your blade a little bit more on the left side of the mouth, to give the ETT more room to get by (Cho 2008).

Also note that different hyperangulated blades have pretty different shapes:

Figure 46: Storz CMAC “D-Blade” on the left, Glidescope “lo-pro” hyperangulated in the middle, and McGrath on the far right

Keep this in mind when inserting your ETT and stylet – the airway may be distorted differently depending on which blade you use.

So you think the patient is successfully intubated… How can you be certain? In the following, we’ll discuss methods of tube placement verification that are routinely used in our hospitals.

1. Tube condensation. Anesthesia people love to exclaim ‘’condensation in the tube!” and will tell you that this is the fastest way to confirm the placement of your tube. (Kelly 1998) showed that the specificity of condensation in the tube with each breath is about 17% for correct ETT placement. Don’t trust this.

2. Auscultation. Also poor. Only about 50% sensitive for detecting an esophageal intubation (Grmec 2004) and about 65% sensitive for detecting a main-stem intubation in the operating room where everything is much quieter than in the ED (Sitzwohl 2010). 

3. Observation of chest rise. Even worse. About 42% sensitive for detecting a main-stem intubation (Sitzwohl 2010 ). Unknown sensitivity for detecting an esophageal tube, but probably poor.

4. Manual balloon palpation. You may see anesthesia attendings do this in the OR. You intubate, then they squeeze the trachea with their fingers to feel where the balloon is, eg (Pollard 1995). This seems to work well for confirmation of depth of the tube in low BMI patients, but there’s no evidence for using it to confirm that the tube is not in the esophagus, and case reports definitely show that it can fail at this (Stirt 1982).

5. Abdominal movement. In an extraordinary study (Andersen 1989) ETTs were intentionally goosed, to see if people could tell if they were in the wrong place by abdominal movement. They guessed incorrectly 90% of the time- worse than chance!

6. Color change aka “Colorimetry”   this is a pretty great way to confirm tube placement, compared to the above options. There’s an elbow shaped piece that comes in an opaque white bag (see figure 48 left), and fits in between the ETT and the bag of the BVM (see figure 48 middle). There are magical chemicals inside that change color according to CO2 content. What SHOULD happen, if the tube is in the ETT and the patient is alive, is that with inspiration the square should turn purple, and with expiration it should turn yellow (see figure 48 right)

Figure 48: “colorimetric” sensor of CO2

After intubation, especially a difficult airway with poor visualization, it is very reassuring to see that first color change, and think “I’ve got it!”, but you should be more cautious. If the patient got some BVM before they were intubated, and a bunch of AIR went into their stomach, or they drank a seltzer water before coming in, and your tube is in their esophagus, you might still get color change as the CO2 sensing chemicals detect the difference in CO2 content of the air coming out of their stomach! Watch for color change after 5-6 breaths before you declare victory. (Salem 2001)

Other unexpected events that can occur:

  • Purple on inspiration and expiration: either you tubed the esophagus, or your patient is dead, and getting poor CPR, and not getting enough blood flow into the lungs to increase the pulmonary CO2 content above ambient levels. Even if CPR is ongoing – reassess that you did not tube the esophagus.
  • Yellow on inspiration and expiration: your colorimeter is broken. This happens if it’s older than 15 months, or exposed to a lot of humidity or other chemicals. Throw it away.

7. Waveform ETCO2 – also called ‘’Capnography” – the gold standard. This is basically the same thing as the color change, except it shows up as a wave-form on the monitor, so everyone can see it. The little connector piece looks like what is shown in figure 49, with little yellow highlights.

Figure 49 Left: ETCO2 capnography piece. Right: in place

It can be connected in between the ETT and the bag of the BVM or in between the ETT and ventilator, and then the yellow plug goes into the special hidden orange doohickey on the monitor. The waveform should pop up on the monitor, and look something like this (ideally):

Figure 50: normal waveform of CO2 on an intubated patient.

Again, when you hook up your ETT and capnography to the monitor and start to see the beginnings of this waveform, it’s very reassuring. BUT! Just like above, if the stomach is full of air and your tube is in the esophagus, you can get a very similar looking waveform for the first several breaths.

Figure 51: deceptive waveform on a goosed patient! (from (Ping 1987)).

The waveform in figure 51 was from a 10 year old boy with an esophageal intubation; the initial waveform is indistinguishable from a normal endotracheal intubation, likely due to air in the stomach from BVM before the intubation (Ping 1987). Just like with colorimetry, you need to wait 5-6 breaths to confirm you’re in the trachea!

8. CXR. This works well for confirming tube depth (should be between 2-6cm from carina). Something like 15% of tubes may be initially either too shallow or too deep (Schwartz 1994), with a higher incidence of too deep placement in women than in men. CXR is NOT good for determining that the ETT is in the trachea instead of the esophagus, although supposedly you can take a 25 degree right-posterior oblique CXR to confirm with some accuracy (Smith 1990). 

 

Section 9: How to insert an LMA

Miss your first pass at intubation and have to bag? Thinking of having another go at it? Maybe trying DL instead of VL? Maybe trying the Bougie? Current expert opinion suggests that you should limit the number of times you try to intubate, and maybe just throw in an Laryngeal Mask Airway (LMA) instead (see difficult airway algorithms from American Society of Anesthesia, British Difficult Airway Society, and All India Difficult Airway Society in appendix). 

Miss your first pass and find that you can’t bag the patient? Don’t worry: such situations are extremely rare in practice, estimated at <1/10,000 people (Heard 2008), but if it does happen, this is definitely an emergency! Reach for the LMA before you reach for a scalpel (unless LMA is contraindicated of course)! 

LMAs can be placed even in patients who would be extremely difficult to intubate, however there is some skill involved. Inexperienced users have a first attempt success rate of about 75% and overall success rate of about 84-94% (Leach 1993), whereas anesthesiologists can generally get an LMA in 98% of patients within 20 seconds (Brimacombe 1993). Seeing as YOU will likely only reach for an LMA after having failed to intubate, it seems worthwhile to read up on and practice this potentially life saving skill. Be sure to do so when on your anesthesia rotation!

For better or worse, there are MANY brands/designs of LMAs out there, and from one day to the next you may find a different type in your airway cart. Fortunately, they all work more or less the same. See below for a common type. 

Figure 52: Labeled LMA (image modified from teleflex.com)

The distal tip fits into the esophagus, to correctly position the cuff over the glottis. How do you put one in? The optimal technique is highly user dependent, but most people agree on the following steps (Pollack 2001):

  • Lube up the cuff – front and back.
  • Put the patient in sniffing position.
  • Grab the jaw / tongue with your left hand, and pull anteriorly (or use a tongue depressor to push the tongue and jaw anteriorly).
  • Insert the LMA pointing it superiorly towards the hard palate initially! (see figure 53, part a).
  • Once you get past the tongue, continue to push posteriorly (see figure 53, part b). The LMA will find its way.
  • Magically, the LMA will clunk into place (part c). You can then inflate it some to get a better seal if you need to (part d).

Figure 53 How to insert an LMA – start by pointing it up into the roof of the mouth (from Whitten 1989).

It’s also worth noting that there ARE a couple of contraindications to LMA use:

  • Aspiration risk. The LMA does not ensure that vomit won’t get in the airway. So if your patient is vomiting, it’s not a great plan. Even if they’re not vomiting, but are at risk, recommendations are to hold cricoid pressure continuously while the LMA is in place (Pollack 2001). Sound onerous? That’s why we usually try to intubate before we LMA.
  • Significant oropharyngeal trauma, that prevents you from getting the LMA in (and also likely will be messy and an aspiration risk).
  • Severe asthma, or other respiratory situations that will require very high airway pressures (Asai 1994) – the LMA doesn’t have as good of a seal as an ETT, and will leak. The maximum airway pressures obtainable on patients getting minor elective surgeries in one study (Weiler 1997) was about 30 mm Hg, but for some percentage of patients, air starts leaking into the stomach at even lower pressures than this (As low as 20 mm Hg in one patient).
  • Laryngospasm – obviously. The glottis is below the LMA.

Section 10: How to Perform Bag Valve Mask (BVM) Ventilation 

When anesthetized, paralyzed, comatosed (or asleep), the muscles of the face and throat relax, and if supine, the weight of the mandible and tongue will cause this structure to move backwards and occlude the airway, causing apnea, hypoxia, and hypercapnia.

Figure 54: when supine and relaxed, the jaw and tongue move posteriorly and the airway collapses. (image from Mayoclinic.org)

 

This is inconvenient, and when it happens, we make moves to open the upper airway so the patient can oxygenate and ventilate on their own. If the airway is open and the patient is still not breathing, and there’s no quickly reversible problem (e.g. naloxone), the person is likely to get intubated. Sometimes between opening the airway and intubation, we will also need to use a BVM to provide respirations to patient. This is extremely commonplace in the OR, where most patients are NPO and low aspiration risk, but in the ED, this can come with higher risk. On the one hand, using a BVM is likely to cause some inflation of the stomach, making vomiting more likely, which is an airway nightmare. 

Opening the airway

As early as 1856, it was observed that patients anesthetized with chloroform were in danger of suffocation by the tongue falling back and the airway collapsing (Hall 1856), with the proposed solution of the time to simplyroll the patient into a prone position so that gravity could relieve the problem. Other researchers developed special forceps for grabbing the tongue and pulling it up and out of the way (which you can still buy on amazon, BTW). The “jaw thrust” maneuver was first described in the 1860s by a dentist (Clover 1868), and basically consists of grabbing the mandibular rami with your fingers and lifting towards the sky. It can also be helpful to use your thenar eminence to press down on the zygoma for counter-traction, as shown in figure 55.

Figure 55: Jaw thrusting (image from Queensland Gov airway management procedures 2021)

 

By performing a jaw thrust, you’re effectively dislocating the jaw out of the glenoid fossa, and lifting the tongue off the retro-pharynx, re-opening the airway.

 

Figure 56: When jaw thrusting, you dislocate the jaw a little bit. Don’t worry, it’ll reduce. (image from (www.pivotalmotion/physio)

Much more convenient than rolling your patient to a prone position or pulling on the tongue with your special forceps.

Another way to open an airway occluded by the tongue is the head-tilt chin-lift shown in figure 57.

 

Figure 57: Head tilt chin lift to open the airway – a less used maneuver in the ED (image from cpraedcourse.com). Although if your patient is just intoxicated and snoring, and does not need aggressive management, this may be a gentler approach to temporarily open their airway than the uncomfortable jaw thrust. Per one study (Guildner 1976), chin lift might even be slightly more effective than the jaw thrust. In practice we usually jaw thrust in the ED, probably because you shouldn’t be flexing or extending the c-spine in most trauma patients, and moreover if we’re manually opening the airway like this in the emergency department, we’re probably also bagging the patient, and it’s easier to jaw thrust while maneuvering the BVM.

 

Bagging / Bag Mask Ventilation

Basically, all of the modern ways of holding a face mask are an attempt to dislocate the mandible forward, re-open the airway, while holding the mask on the face with a good seal. The first challenge is putting on the mask. A useful technique (Whitten 1989) is to start with putting the mask on the bridge of the nose, and then lay it down over the mouth. If the person is old or cachectic, you may need to squish their cheek tissue up into the mask to make a good seal on the sides. Once you’ve formed the seal, jaw thrust up with two hands to open the airway, and you’re ready to ventilate!

Figure 58: Steps of applying the BVM mask and making a good seal (image from Whitten 1989). To do this well, it’s a little more complicated than you expect.

 

As for howhold the mask while you ventilate, there are basically 3 options. They consist of the “C-E method” of one handed ventilation, the standard two-handed technique, and the “alternative” two-handed technique:

Figure 59: Different hand positions for BVMing, taken from (Hart 2013)

Data is pretty convincing that the two handed techniques work much better than the one handed C-E clamp (Joffe 2010), although there doesn’t seem to be much difference between the two handed techniques (Hart 2013).

That said, this is not easy. Studies have shown that a thick neck, presence of facial hair, and a high BMI are all significant predictors of difficult bagging (Cattano 2014). If the patient is paralyzed, bagging may become easier (Warters 2011), but the stakes are also higher.

Trouble shooting

  • With any of these techniques, it is important to lift the jaw up into the mask, and not push the mask (and jaw) down into the face, which would further occlude the airway.
  • If you need to use the one hand technique, it’s best to start with a two handed jaw-thrust to dislocate the jaw and get a good seal, and then use one hand to keep the airway in place while the other hand squeezes the bag. 
  • Try to listen / feel for where the air is leaking out from the mask, and adjust your grip to fit. 
  • If you have a good seal but are not getting good chest-rise, you may need to adjust your jaw thrust.
  • Doing this for more than a few minutes, especially if the patient is not paralyzed, can seriously cramp your hands. Ask for someone else to help do the BVMing if you’re planning to do the intubation, as you need your hands to be relaxed. RTs are generally trained pretty well in using the BVM.

Adjunct Airways

One way to trouble shoot your difficult-to-bag patient is by putting in an “airway adjunct”, i.e. an oral airway (“OPA”) or a nasal trumpet (“NPA”), especially if you’re experience significant resistance providing bag-mask ventilations. These simple tools can help relieve upper airway obstruction and improve your bagging.

Figure 60: oral airways (image from line2ems.com) and nasal “trumpets” (image from Lin 2013)

 

You should try to grab an airway adjunct that fits your patient. Placing the wrong size OPA in particular can worsen the problem by pushing the tongue back into the oropharynx and further blocking airflow. The correct sized OPA should measure the same distance as from the angle of the mouth to the earlobe. The correct sized NPA will measure from the nare to the earlobe. Easy!

 

Modified Nasal Trumpet:

If your patient is really hard to bag, i.e. their jaw is clenched tight, but you get a nasal trumpet it, you can even try the ‘’modified nasal trumpet’’ maneuver (Beattie 2002), as shown in figure 61.

Figure 61: the modified nasal trumpet, from (Beattie 2002)

This technique uses an ETT adapter to hook your nasal trumpet directly up to a BVM. The first step is to make your modified nasal trumpet. Choose a large nasal trumpet, and cut an extra hole near the end that goes in the airway, (dotted ellipse in drawing) to help prevent it from being occluded, and then steal the connector piece off of an ETT and ram it into the external facing end of the trumpet. Now put this in the person’s nare, connect the BVM, and start bagging, using your other hand to occlude their contralateral nare and their mouth, as shown in figure 61. In Beattie’s original report, he used this with great success in “can’t intubate, can’t BVM” situations and avoided many surgical airways. If for some reason it’s impossible to open the mouth, you can also plausibly intubate in this situation, by using the fiberoptic cable through the contralateral nostril (not covered in this guide).

Section 11: How to put it all together and work as a team

This is very important. You are just one piece of a large team with the overarching goal to intubate the patient. The senior resident or attending may ask you what medications you would like to use, what your plan is, etc. Or they may just tell you. They may help you set up the head of the bed for intubation, or they may leave that to you. 

At some point, everything will be ready. RT will be there. The meds will be drawn up. The patient will be positioned, etc. You’ll have all of your gadgets at your disposable. Someone will push the meds, and then you should watch the patient very carefully. Whether succinylcholine or high dose rocuronium is your paralytic of choice, it’ll likely take at least 50 seconds for them to be fully paralyzed, giving you the best conditions to intubate. You should take note of the exact time the paralytic is pushed, and keep mental track of how many seconds have elapsed since. At the same time, you should keep a trained eye on your patient: 

Once the patient stops breathing, or appears to be unconscious, you can test them by touching their eyelash with your finger to see if they move. If this is RSI (e.g. a bariatric or pregnant patient, or at risk for vomiting–most patients you’ll be intubating in the ED will be with RSI), just keep holding the mask on their face so they get some passive oxygenation. If you’re instructed to bag the patient, then you should do a jaw thrust, put on your best C-E grip, and start bagging, watching the chest rise and the ETCO2 for feedback. If things are not going well, attempt to maintain the jaw thrust and mask with two hands, and ask someone to bag for you. If things are still not working, stop and put in an oral and/or nasal airway, and try to bag again. Once the patient has started to fasciculate (if sux), or they appear to be paralyzed (if roc), or the appropriate ~50 seconds has passed, the attending will tell you that it’s time to intubate, so go for it. 

During the procedure, report out loud everything you are doing and seeing. For example: “mouth is loose and easy to scissor open, I’m sweeping the tongue, I see oropharynx… I see epiglottis… I see arytenoids…I see the cords. I’ve got a grade 1 view… tube is at the cords… tube is through the cords” and someone will pull your stylet for you. Saying all of this out loud can be challenging, but will place everyone at east. If you need BURP, ask for it (the attending may just do it without asking) . If you have a bad view, or no view, say so! They will not fault you for being unable to intubate, but if you leave everyone hanging while you’re futzing around with a difficult airway, they will be rightfully upset.

Maintain a loud, clear, but calm voice. If you start sounding like an anxious crazy person, everyone will get nervous and that’s no good.

Once the tube is in and the balloon is up, RT (or someone else) will hook it up to the BVM and start bagging. YOU should hold on to the ETT for dear life (literally) until it’s very firmly secured to the patient’s head. Horror stories of accidental extubations by over-excited RTs or other “helpers” are real. Don’t let someone pull your tube out. Trust no one. Good luck!

Section 12: Appendices, Algorithms, and Trivia

 

1)         ASA Difficult Airway Algorithm (For OR patients):

Figure 62: The difficult airway algorithm from the American Society of Anesthesiologists (Apfelbaum 2022) for use in the OR. Note that “postpone the case” is one of the endpoints – obviously not an option in the ED.

 

2) British Difficult Airway Society Algorithm (critically ill)

Figure 63: Algorithm from the “Difficult Airway Society” (Frerk 2015). Note that cricoid pressure (Sellick maneuver)  is used in all RSIs in the UK as a default – but if laryngoscopy is failing they recommend stopping this, along with trying BURP or bimanual laryngoscopy.

3) All India Difficult Airway Algorithm for ICU patients

Figure 64 (from Myatra 2016) Indian guidelines- similar to British in defaulting to cricoid pressure. Note default to LMA (SAD: “supraglottic airway device”) after failed intubations, whereas older British guidelines seem to recommend LMA only if an expert at LMAs is available.

 

4) Choice of Paralytics… “Roc” vs “Sux”

What follows is a short list of some of the benefits of rocuronium, for the interested reader.

  • Succinylcholine has many contra-indications and potential side effects, like hyperkalemia, malignant hyperthermia, etc, while rocuronium has almost none
  • Rocuronium’s onset time is dose dependent. The higher the dose, the faster. “Double dose roc” at 1.2mg/kg has an onset of paralysis time (about 55 seconds) almost the same as regular dose 1.0 mg/kg succinylcholine (50 seconds) (Magorian 1993) Even higher doses of roc may work even faster (Heier 2000), but have not been well studied. 
  • When succinylcholine makes the patient fasciculate all their muscles, they actually use up some oxygen, so a patient who gets succinylcholine will desaturate before they would if they’d gotten roc. How much? Almost 40 seconds sooner! (Tang 2011). If you’re having a hard time intubating, 40 seconds is a long time.
  • Succinylcholine takes about 10 minutes to wear off, while sugammadex at 16 mg/kg can reverse rocuronium in less than 3 minutes (Lee 2009). If you’re in a can’t intubate, can’t bag-valve-mask situation, 3 minutes will feel like a very long time, but it’s much better than 10. Be aware that not everyone has sugammadex in their pocket though.
  • You can actually make rocuronium work even faster if you give the patient 60mg/kg of magnesium about 15 minutes before intubation, (El Kobbia 2015), although this is rarely practical in the ED.

5) ETT size selection

Up until the 1980s, anesthesiologists generally followed Magill’s 1928 edict to use “the largest endotracheal tube which the larynx will comfortably accommodate” (Farrow 2012), often 8.0-10.0 for women and men respectively. However, later research revealed a very strong association between extra-large ETTs and the development of laryngeal or tracheal stenosis (Gelbard 2015) and vocal cord edema (Colton House 2010), which complicates extubation and future intubations. Furthermore (Stenqvist 1979) showed that decreasing the ETT diameter, while it may increase max pressures seen by the ventilator, does little to change the pressures seen by the airway in healthy patients, even for tubes as small as 6mm. This, and the commonly held conviction that using a smaller ETT makes intubation easier (see e.g. Frerk 2015), has led to a trend towards using smaller ETTs. 

These days, if you ask an anesthesiologist in the OR, they will likely recommend a tube size based on that patient’s anatomy and tracheal diameter. You may hear the rule of thumb of “7.0 for women and 7.5-8.0 for men”, based on their tracheal size or something like this. Actual morphological studies of larynxes based on CT scans show, however, show that tracheal size is mainly a function of the person’s height, and after correcting for height, there is no dependence on sex (Coordes 2011). So if you’re going to follow anything, judge by the person’s height. Figure 65 shows one popular nomogram for picking ETT size based on height:

Figure 65: ETT recommended size and tracheal diameter as a function of height (Coordes 2011)

Note that the optimal tube size changes A LOT with increase in height. For every 4 inches of height, you go up an entire mm of tube diameter, e.g. from 7.0 to 8.0. The average height of a male from Holland is just over 6 feet, and that of a male from Guatemala is just under 5 feet 5 inches (Rodriguez-Martinez 2020). That’s the difference between a 9.0 and a 7.0 ETT! Maybe we should have a tape-measure in the airway box? 

If your patient needs to be emergently bronched, e.g. they are being intubated for massive hemoptysis, or pneumonia with copious thick secretions, then getting an 8.0 or maximum 8.5 tube in would be very helpful, as it allows better continuous ventilation while the bronch is in. (Our esteemed MICU colleagues have endorsed this opinion)

How about asthma? As we learned in medical school, per Pouiselle’s law, airway resistance will go up dramatically with decreasing ETT sizes, which could be particularly problematic in severe asthma exacerbations when the inherent anatomical airway resistance is so high that it causes air trapping. Recently, observational data in intubated asthma patients has shown higher mortality rates associated with smaller ETTs (Kashiouris 2022) with the mortality of a 6.5 tube being about twice that of a 8.0 tube. Whether this is due to air trapping, or due to the increased rate of mucous plugging and hence need for bronchoscopy in these patients, or this is just a spurious correlation caused by some other factor not being controlled for in their study, getting a bigger tube in your status asthmaticus is something to aim for.

All that being said, any airway is better than no airway. If you’re having a hard time passing a large ETT or you’re expecting a narrow airway, a 6.0 is infinitely better than nothing. Get a tube in.

6) Random trivia

Question:   Which paralytic has to be dosed by actual body weight, and which by ideal body weight?

Answer: succinylcholine is actual body weight, and roc is ideal.

Question:  Which paralytic can you give IM?

Answer: succinylcholine, although dose is much higher at 3-4 mg/kg, and it might take 3-4 minutes to be paralyzed. Note that rocuronium will paralyze if given IM (it comes from curare- which was used in the Amazon to make poison arrows, which are certainly not given IV), but time to paralysis and duration is unpredictable 

Question: Let’s say you don’t have 3-4 minutes to wait for paralysis after IM succinylcholine in the deltoid – you need something faster! What can you do?

Answer: In principle, could inject into the tongue. This is not commonly done, but there were many anesthesia studies from the 90s on this. Seemingly the tongue is much more vascularized than other accessible muscles, and intra-lingual succinylcholine can paralyze within about 2 minutes. Obviously increases the risk of a bloody airway. Obviously don’t do this without talking to your attending first. 

Question: In what order are the muscles paralyzed, and in what order do they come out of paralysis?

Answer: The diaphragm and laryngeal adductor muscles are paralyzed first, followed by the facial muscles and the extremity muscles. They are released from paralysis in the same order – the larynx and diaphragm will start working again before the hands do. (Hemmerling 2000).

Question: Let’s say that you paralyzed your patient with sux or roc, but you’re worried that your patient is seizing. Besides an EEG, is there any way that you can tell?

Answer: Check their pupillary reflexes. They should still maintain them after paralysis (Caro 2011), but will not if they’re seizing (Baumgartner 2001). Keep in mind that induction agents (e.g. midazolam) may interfere. 

Question:  How can your attending tell if the tube goes through the cords from the foot of the bed?

Answer: Putting the tube through the cords causes a sudden increase in HR, which some studies have shown to be up to 20 beats / minute on average (Dashti 2014), so if they’re listening to the monitor, and suddenly hear tachycardia, they can guess you’ve probably got it. (Note: you obviously can’t rely on this for tube confirmation- you still need to use capnography)

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