In this day and age with video-laryngoscopy (VL) rapidly becoming the standard of care for orotracheal intubation (OTI) one might rightly ask if there is still a need for a chapter on direct laryngoscopy (DL). However, while VL is gaining ground on DL it has yet to replace it as the most common device employed to facilitate OTI, and it will remain a vitally important skill to master for difficult and failed intubation rescue, and in parts of the world that cannot afford or do not have access to VL.

What Is the History and Evolution of Direct Laryngoscopy and Tracheal Intubation?

In the modern era, DL is almost exclusively associated with tracheal intubation, even though the procedure was initially developed for diagnosing and treating laryngeal pathology. Following the development of mirror laryngoscopy in the 1800s (Czermark and others), Kirstein reported the first DL in 1895.¹ Over the next 20 years, the basic tenets of the procedure were refined by surgeons interested in laryngeal examination and surgical exposure.

A step-wise approach, the focus on epiglottoscopy, recognition of posterior laryngeal landmarks, optimal positioning for laryngeal exposure, and the benefits of external laryngeal manipulation and head elevation, etc., are all detailed by Chevalier Jackson² in his 1922 text, Bronchoscopy and Esophagoscopy, A Manual for Peroral Endoscopy and Laryngeal Surgery.

With the evolution of modern anesthesia, the original straight laryngoscope designs by ENT surgeons gave way to instruments specifically designed for tracheal intubation, such as the straight Magill (1930)³ and Miller blades (1941)⁴ and the curved Macintosh blade (1943).⁵ It was also in this time period that the modern design of a detachable blade and battery handle became commonplace.

Between the 1930s and 1970s, many different laryngoscope blades were designed to facilitate intubation (e.g., Wisconsin, Phillips, Guedel, etc.), but the Magill, Miller, and Macintosh models (albeit with some modifications) remain universally used, and in most settings, are the only laryngoscope blades available.

The development of flexible fiberoptics, subsequent attachment of fiberoptics to rigid blades (Bullard laryngoscope, WuScope, etc.), and more recently video laryngoscopes (Glidescope, McGrath, Storz Video MAC, etc.) have narrowed the clinical role of standard, line-of-sight (LOS), DL, and now there is a wide array of indirect visual devices for both diagnostic imaging of the larynx and tracheal intubation. Direct laryngoscopy remains the predominant method of tracheal intubation. Alternative devices, however, are being increasingly deployed for both routine and anticipated “difficult laryngoscopy.”

What Are the Principal Design Components of Laryngoscopy Blades and How Do they Work to Facilitate Endotracheal Intubation?

Laryngoscope blade design, light, and battery systems affect procedural performance since they impact on illumination, laryngeal exposure, and endotracheal tube (ETT) delivery. This holds true for both straight and curved laryngoscope blade designs, but because these designs function differently, there are different considerations (see below).

The principal components of a laryngoscope blade are the spatula (that passes over the lingual surface of the tongue) and the flange that is used to direct the tongue (Figure 9–1), a fluid filled non-compressible structure, to the side of the mouth and into the mandibular space (the space below the tongue). This concept of “mandibular space volume” is particularly important in clinical practice as the practitioner evaluates for difficult laryngoscopy and intubation (see Chapter 1).

Straight blades, such as the Magill blade (see Chapter 1, Figure 1–1), were originally designed to “pick up” the epiglottis and elevate it directly, while the curved Macintosh type blades are intended to be advanced into vallecula and indirectly elevate the epiglottis by applying pressure to the hyoepiglottic ligament. These factors illustrate two distinguishing features of these blade designs: that straight blades are inserted more deeply than curved blades; and that curved blades have an atraumatic tip design to reduce the risk of vallecular injury.

Because laryngoscopy was originally an operative technique where the practitioners needed their dominant right hand (85% of the population is right hand dominant) to be free to operate, the laryngoscope became by default a left-handed instrument.

Laryngoscopy and intubation are performed through the right side of the mouth. The left hand is used to insert the laryngoscope blade into the mouth to expose the glottis. The right hand is then free to perform a variety of tasks including the insertion of an intubation aid (e.g., Eschmann Tracheal Introducer, [ETI]), manipulate the larynx, lift the head, suction the airway, and ultimately, pass the tube.

Early pioneers, such as Magill,³ employing straight blades recognized that tongue displacement to one side facilitated laryngeal visualization, particularly if the blade of the laryngoscope was inserted in the corner of the mouth and along the paraglossal gutter. Importantly, it was recognized that this “paraglossal” or “retromolar” technique optimized the laryngeal view mostly because it shortened the distance between the teeth and the larynx (i.e., the molars are closer to the larynx than the incisors). The other benefit of right paraglossal laryngoscopy is that the rigid laryngoscope blade impacts the molar teeth rather than the relatively more fragile central incisors. The flange of the laryngoscope remains a threat to dentition and should never be leveraged backward against the teeth.

Straight blade laryngoscopes tend to have smaller displacement volumes (defined by the dimensions of the spatula and flange) than curved designs. It is logical, therefore, that straight blades (and a paraglossal approach) are favored in patients who have a small mandibular volumes into which the tongue is displaced (or “compressed”) during DL. Examples of such patients are small children (below the age of 8, but especially below age 5) and adults who have a receding chin.

What Are the Variables that Determine the Illumination Created by a Laryngoscope Blade?

Illumination is critically important for DL. Bright light is necessary for tissue edge and color discrimination, and the identification of tissues and structures. This is particularly important in preterm infants where the appreciation of subtle color differences is critical to intubation success.

Laryngoscope lighting systems can be divided into those with a light source mounted directly on the blade (bulb-on-blade), and those in which the light source is at the top of the handle (bulb-on-handle).

Bulb-on-blade designs (sometimes referred to as conventional blades) have a simple electrical connection between the bulb socket on the blade and the handle (with enclosed batteries). This connection is very robust and less subject to malfunction than the spring-loaded, on-off lights used with bulb-on-handle systems. These removable bulbs can usually be replaced if they fail. This feature confers the risk that should the bulb become loose it may flicker during operation, or worse yet, become dislodged and lost into the patient.^6,7 To eliminate this risk, some manufacturers fuse the bulb to the blade rendering the bulb non-replaceable.

Laryngoscope bulbs for both designs are of several types: incandescent filament (tungsten with halogen gas), xenon gas, and light-emitting diodes (LED). The bulb itself can have either a frosted or clear lens, and may incorporate a reflector (common with bulb-on-handle designs).

Compared to other light producing systems, LED bulbs use very little energy, operate with less heat, and have a much longer life span, thereby eliminating bulb replacement as a major concern. They now can be produced at less cost than other bulbs and produce brilliant light. The light from an LED tends to be whiter and bluer than traditional bulbs. All of the newer intubation devices (video laryngoscopes, mirror laryngoscopes, chip-on-stick CMOS imaging devices, etc.) use LED lights.

With bulb-on-handle systems, a light-conducting fiber, made of either glass or plastic, conveys the light from the top of the handle to the distal portion of the blade. Although such blades are often called “fiber-optic,” they have no optical fibers, per se, and a more appropriate term is “fiber-lit.” Glass fibers conduct light more efficiently, but cost significantly more. Disposable blades commonly use a light-conducting bundle made of plastic, whereas non-disposable fiber-lit blades all use glass fiber bundles. In the United States, any blade or handle that uses fiber illumination has a green dot on the blade base and a green circle at the top of the handle (commonly referred to as a “green-line handle”). It is important for practitioners to appreciate that fiber-lit blades and handles and conventional blades and handles are not interchangeable.

A critical and essentially unexamined area of laryngoscope illumination involves batteries.⁸

Alkaline batteries have a gradually declining discharge curve. Failure to appreciate and rectify this declining illumination may compromise DL by low light, heralded by a difficult or failed intubation.

Lithium batteries have a much flatter, higher discharge curve than alkaline batteries, but fail precipitously once the energy output falls below a certain threshold. Lithium batteries are much more expensive and generate more heat than alkaline batteries.

Some manufacturers, especially those producing high-quality fiber-lit blades, offer nickel-metal-hydride rechargeable battery systems, which produce very intense light when combined with a xenon bulb and glass fibers. While the light output from these high-end fiber-lit systems is impressive, they are very expensive.

Newer LED technology has the potential to rival the light output of these systems at a fraction of their cost, draw little energy, and are offered in a single-use, disposable, bulb-on-blade design.

Regardless of the type of light, the intensity of light reaching the distal end of a laryngoscope blade is dependent on the distance the light must travel. This phenomenon is governed by the inverse square law of physics:that is if the distance from the light source to an object is doubled, the resultant amount of light energy reaching the object is reduced to one quarter of the original amount. So, generally, blade designs with shorter light-to-tip distances create more intense distal light. This produces substantial variability in the amount of light emitted by different combinations of blades and handles used in clinical practice. In a study conducted in emergency departments, there was a 500-fold difference in light output between the best and worst blade-handle combinations.⁹

Few clinical settings monitor the light output with light meter testing. Lighting standards in dentistry or surgery recommend 5000 lux.¹⁰ While there is no well-accepted light intensity standard for the laryngoscopes, the International Organization for Standardization has suggested 700 lux as a minimum light output for laryngoscopes.¹¹ In the presence of blood, secretions, and vomitus, common to emergency airways, more light is needed to discriminate landmarks.

What Are the Distinguishing Features of Commonly Used Curved (Macintosh) Blade Designs?

The term “Macintosh blade” is generally used to mean any curved blade. However, since Macintosh’s⁵ original description in 1943, several variations have been produced that are distinguishable by their flange height, flange shape, light position, and light type. These designs are commonly designated by their geographic manufacturing origins, i.e., American (commonly known as “Standard”), English (commonly known as “Classic”), and German designs. The common features are a gently curved spatula and a large reverse Z-shaped flange (Figure 9–1).

American blades closely follow Macintosh’s original description, that is, a large vertical, square-shaped, proximal flange that does not extend to the distal tip, coupled with a bulb-on-blade illumination system. The English design has a smaller, curvilinear proximal flange that runs all the way to the distal tip, and also uses a conventional light. Heine of Germany developed a fiber-lit blade that follows the English contour in terms of a short proximal flange. A large rectangular-shaped 5-mm glass fiber bundle is incorporated in the flange. The English and German designs have a much shorter light-to-tip distance than the American design (Figure 9–2). Most American designs use a frosted bulb, while most English designs have a clear lens. American and English designs now offer fiber illumination options. Numerous manufacturers around the world now offer “American,” “English,” and “German” curved blades, and many blades have a mix of features.

It is interesting to note that Macintosh envisioned one adult size for his blade (corresponding to approximately a Macintosh size 3). Market demand leads to the current variety of pediatric and adult sizes available. Size selection is largely a matter of patient’s size and practitioner’s choice. No matter the size chosen, it should be noted that the most common error of the novice is inserting the blade too deeply and into the upper esophagus before visualization is performed. The shorter light-to-tip distance (and light source common to German or English designs) also provides better illumination relative to the American design.

A recent variation of the Macintosh design is the McCoy (also known as Corazelli-London-McCoy [CLM]) levering laryngoscope blade (Figure 9–3). This blade is a Macintosh design with an articulating distal tip that when activated is intended to elevate the tissue at the base of the tongue (improving epiglottis lift and laryngeal exposure). This blade has become quite popular in the United Kingdom (where it originated), but published clinical investigations have reported mixed results.^12–17

What Variations Exist Between Miller Blade Laryngoscope Designs?

Robert Miller’s straight blade design in 1941 adapted the straight shape of early laryngoscopes, in particular that of Magill (see Figure 1–1), but added a slightly upturned distal tip and narrower flange.⁴ The flange had a compressed D shape (when viewed longitudinally) with a height large enough to accept a 37 French Argyle tube. Compared to tubular-shaped blades (Jackson-Wisconsin, for example), the much shallower proximal flange was intended to minimize dental injury (Figure 9–4). The light was situated at the distal tip on the right side of the spatula, opposite the flange side, and tilted toward midline (Figure 9–1).

Since Miller’s original description, various manufacturers have compressed the flange height, and some have changed the bulb location (to the left flange edge, or recessed within the flange). Designs with light sources located on the exposed edge of the left flange are less preferred by some since a light at this location can become embedded in the tongue with resultant poor illumination. Most Miller designs currently made for adults cannot accommodate an adult-sized cuffed ETT down the barrel. In addition, tube passage down the barrel blocks the LOS to the target. The very narrow design of modern Miller blades necessitates careful paraglossal placement (the small flange cannot sweep the tongue) and the extreme right corner of the mouth (which often requires manual retraction by an assistant) must be used for tube delivery. Alternatively, an ETI can be employed. Another challenge of the narrow flange straight blades is that it makes landmark recognition down the barrel difficult.

What Is the “Straight-Blade Paradox?”

Landmark recognition and ease of tube delivery improve as the flange height and spatula size of a straight blade are increased. Paradoxically, it gets harder to introduce the blade alongside the tongue, and reach the larynx, as the displacement volume of the blade increases. This was known to Miller, who shortened his flange height, but left the resulting D-shaped barrel large enough to accept an ETT.

Straight blade designs with larger flanges (and spatulas) than the Miller design include the Phillips (a 2/3 small “C”-shape flange), Wisconsin (a higher, nearly full “C”-shaped flange), and the Guedel (a very large, sideways “U”-shaped flange and spatula) (Figure 9–4).

The Henderson straight blade has small incomplete 2/3 “C”-shaped flange that is large enough for tube delivery. It also has a uniquely visible distal tip (a knurled edge at the distal blade tip is visible when viewed down the barrel), and a large, recessed, fiber bundle light source (Figure 9–5).

Apart from the McCoy and Henderson Blades Already Mentioned, Are there Other Recent Blade Designs that Might be of Use?

The Dorges universal blade is intended to replace Macintosh size 2-4 blades with one blade for all patients from age 1 to adult.¹⁸ The curve is much reduced, the spatula is tapered from proximal end to distal tip, and the proximal flange height is very short (15 mm), allowing it to be used with children and those with limited mouth opening, while at the same time permitting deeper insertion in larger adults owing to its length (Figure 9–6).

The Grandview blade is an emergency blade for adult patients that is available in two sizes.¹⁹ It combines a very widen spatula with a slight overall curve and a narrow proximal flange (Figure 9–7). The resulting blade can be used to lift the epiglottis directly or indirectly.

What Optical and Biomechanical Considerations Should Practitioners Appreciate When Performing Direct Laryngoscopy?

Direct laryngoscopy is a procedure with inherent visual restrictions. Visual restrictions are created by the degree to which the mouth opens, the teeth, the tongue, the long axis view down a laryngoscope blade, and the structures about the laryngeal inlet that surround the glottic opening. Laryngeal anatomy, which is exposed in piecemeal fashion initially, must be recognized when viewed down this restricted visual space. In many instances, only a small posterior portion of the glottic opening may be visible. Passage of the ETT further adds to the visual challenge. It is critical for practitioners to know laryngeal anatomy in detail, to anticipate the sequence and appearance of structures as they come into view, and to be aware of how visual restrictions and biomechanics impact on laryngeal exposure and tube delivery.

What Is the Best Way to Maximize Mouth Opening and Jaw Distraction for Laryngeal Exposure and Tube Insertion?

As has been previously mentioned, employing the right corner of the mouth for laryngoscope blade insertion and tube passage is essential. A paraglossal approach is absolutely essential with straight blades. Even with curved blades, midline placement of the blade must be avoided because it will create “tongue flop” on each side of the blade, restricting glottic exposure and tube delivery.

The amount of mouth opening possible is a function of jaw distraction, and head and neck positioning. Positioning that facilitates jaw distraction and mouth opening is important in all patients, but most critical in the obese. Supine patients without cervical spine immobilization or known cervical pathology are optimally positioned for laryngoscopy when the external auditory meatus and sternal notch are horizontally aligned when viewed from the patient’s side (see Chapter 20, Figures 20–1 and 20–2). This is called “ear-to-sternal notch” or “ramped” position.

The traditional “sniffing position” is created by a combination of neck flexion and head extension at the atlanto-occipital joint. Ear-to-sternal notch positioning usually requires 8 to 10 centimeters of elevation under the occiput, generally much more head elevation than that produced by the standard “sniffing” position. Furthermore, standard sniffing position posture fails to take into account size-related anatomical variations of the respiratory tract as it transitions from the thorax through the head and neck. On the other hand, ear-to-sternal notch positioning takes this variation into account permitting external landmark-based patient positioning to be individualized. These anatomical variations are most frequently appreciated in individuals who are obese and morbidly obese. In such patients, a ramp may be several feet high and incorporate support under the upper torso and shoulders as well as the head to achieve proper alignment. Head elevation and ramping in this manner optimize laryngoscopy, and while at the same time offer improved gas exchange mechanics.

When performing laryngoscopy with the patient supine, along with ear-to-sternal notch positioning, the face plane of the patient should be parallel to the ceiling (see Figure 20–2). A common error is to overextend or tilt the head backwards.² Atlanto-occipital extension may push the base of tongue and epiglottis against the posterior hypo-pharyngeal wall. Not only does this make recognition of the epiglottis more difficult upon blade insertion, but also narrows the space available to pass the laryngoscope and restricts laryngeal exposure. Extension alone may also create tension on the anterior neck muscles opposing simultaneous efforts to open the mouth and distract the jaw.

Successful laryngoscopy in this position requires that the patient’s head be below the practitioners xiphoid process, a position recommended by some texts. The reason for this is that increasing head elevation dynamically during laryngoscopy if laryngeal exposure is inadequate is made easier.²⁰ Dynamic head elevation cannot be done on the morbidly obese and these patients must be ramped into a proper position in advance (see Figure 20–2).

Mouth opening in the anesthetized or unresponsive patient usually occurs with head and neck positioning. In the event it does not, it can be achieved by simply pushing the chin in a caudad direction or by employing the cross-fingered or “scissors” technique. This technique provides a more controlled and effective force than simply extending the head on the neck.

What Is the Optimal Position for Laryngoscopy in Patients with Known or Suspected Cervical Spine Injury? Is It Safe to Perform Direct Laryngoscopy?

Direct laryngoscopy has been shown to be safe in patients with known or suspected cervical spine injury, but it should be performed with manual in-line immobilization (MILI) (see Chapter 17). There has been considerable attention and controversy regarding airway management in the known or presumed c-spine injured patient.^21–23 Some would argue that this concern has led to unnecessary delay in managing the trauma airway, a decision which in some cases could result in increased morbidity and mortality (e.g., hypoxemia and/or hypercarbia in head injured patients). As a result, Advanced Trauma Life Support (ATLS) has backed away from an earlier recommendation that C-spine imaging precede airway management. Furthermore, there is little evidence to support secondary spinal cord injury directly attributable to airway management.^22–24 Despite the fact that MILI does not completely prevent c-spine motion, it remains a recommendation. Care should be taken to ensure proper application of MILI in such a manner that mouth opening is not limited. Mouth opening is markedly limited with a collar in place where epiglottis-only views (or worse) can occur in more than 60% of cases.²⁵ Properly performed MILI will reduce the incidence of an epiglottis-only view to 22%.²⁶

Research comparing intubation devices have revealed no convincing superiority of any device over well-performed DL in terms of limiting c-spine motion.²¹ The major priority in managing suspected c-spine injured patients is how to optimize view on laryngoscopy. Indicated airway management should not be delayed in fear of causing secondary spinal cord injury. The use of alternative devices, such as optical stylets or VL may help overcome a challenging view, although simple maneuvers, such as the application of optimal external laryngeal manipulation²⁷ (OELM or BURP, Backwards Upwards Rightwards Pressure²⁸) and the use of an ETI (commonly referred to as a “gum elastic bougie”) are equally effective in managing the airway in a trauma patient with a suspected c-spine injury.²¹

Ear-to-sternal notch positioning cannot be used in such patients. The front of a cervical collar should be removed in order to permit jaw distraction. It is also helpful to drop the foot end the stretcher while keeping the stretcher straight (i.e., “Reverse Trendelenberg”). This positions the airway higher than the stomach and may prevent passive regurgitation and improves pulmonary mechanics. An assistant must maintain MILI while laryngoscopy is carefully performed.

How Should the Laryngoscope be Gripped to Minimize the Work of Laryngoscopy While Maintaining Fine Control of the Blade Tip?

The mechanics of laryngoscope lift are slightly different with curved versus straight blades. With the curved blade, the tip of the blade is guided into vallecula to depress the underlying hyoepiglottic ligament, lifting the epiglottis forward away from the glottic inlet. With straight blades, the tip of the blade lifts the epiglottis directly. Both curved and straight blade handles should be gripped with the tips of the fingers where the handle meets the proximal blade (Figure 9–8). The handle should be gripped low enough so that the blade is essentially an extension of the forearm. Holding the handle higher increases the length of the lever arm requiring significantly more muscular effort. When properly gripped with the thumb pointing upward on the handle, fine control and effective mechanical advantage are achieved, and levering on the upper incisors is less likely to occur. Laryngoscopy is a delicate procedure, mostly dependent on gentle positioning of and correct vector forces at the blade tip. When properly positioned, the amount of force required for most patients is minimal and can be achieved by a light grip. When the blade tip is not correctly positioned, excessively forceful lifting will usually not correct the problem.

Another way to maximize lifting efficacy with minimal muscular effort is to keep the left elbow adducted to your side (roughly the anterior axillary line), not pointing outward. With the elbow in, the handle is gripped down low, the forearm is kept straight, and body weight can be used to rock forward slightly so that minimal arm strain occurs. Force is efficiently transferred along the forearm and down the long axis of the blade.

How Is the Larynx Sighted During Direct Laryngoscopy and Is Performance Improved by Assuming a Distance as Far as Possible from the Target?

Contrary to popular belief and traditional instruction, even with an extended arm position, it is not possible to simultaneously see the larynx during laryngoscopy with both eyes.²⁹ This is due to the inherent visual restrictions of DL, created by the opening of the mouth, the teeth, the tongue, the laryngoscope blade itself, and the structures of the laryngeal inlet. Visually, DL is similar to looking down a narrow pipe at a target the size of a quarter, from a distance of 14 to 16 inches.

Both eyes can be open during the procedure, but sighting of the larynx is with the dominant eye only; the brain subconsciously blocks out the non-dominant image through a process called “binocular suppression.” The same phenomenon occurs when looking through a peep-hole in a door, or when sighting during target sports. In situations without visual restriction, the right and left eyes have slightly different perspectives on an object, due to the distance separating the eyes in the skull. These slightly disparate views are fused into a single stereoscopic image. This cannot happen with the visual restrictions created during laryngoscopy; stereoscopic sight cannot be achieved. Because binocular suppression occurs subconsciously, even experienced laryngoscopists may not be aware of which eye they use to sight the larynx.

The monocularity of laryngeal sight during laryngoscopy is evident when viewing novice intubators attempting laryngoscopy for the first time by noting a subtle side-to-side head rotation, intermittently sighting the target with one eye and then the other.

The old adage that “experienced laryngoscopists maintain a distance from the target, while novices climb into the mouth” is due not to experience but rather restrictions on accommodation that occur with age. By the mid-forties, the near visual accommodation point begins to move out approximately 2 to 3 centimeters per year. By mid-fifties regardless of your underlying acuity, presbyopia results in the near focus point being at about arm’s length. Younger practitioners have the accommodation flexibility to focus on near objects. These changes are exacerbated in low light conditions. The amount of light needed for laryngoscopy by the same practitioner is different at age 40 versus age 50 and 60; more light improves the near focus ability significantly and is another reason for using laryngoscope systems with good light output.

Is It Beneficial to Identify Ocular Dominance, Acuity, and Accommodation Distance in Trainees and How Is This Done?

Ocular dominance, visual acuity, and accommodation should be assessed at the start of procedure training and in all practitioners on the steep curve of presbyopia (mid-forties).

Ocular dominance is tested by having the practitioner perform DL on a training mannequin. After the practitioner confirms that the larynx is sighted, instruct him or her not to move their head. Selectively cover each eye, individually. When the non-dominant eye is covered, the laryngeal view is not compromised; when the dominant eye gets covered, the larynx will no longer be sighted (or it will be seen partially, off angle). One cannot change one’s natural ocular dominance. Eyedness tends to follow handedness assuming there is not unequal acuity, and since majority of the population is right-handed, most practitioners are also right-eyed. Persons who have a difference in visual acuity (wear lenses), or are left-handed, have a greater likelihood of being left-eyed when it comes to laryngoscopy.

Identification of ocular dominance, formal visual acuity, and accommodation testing is valuable to the trainee to proactively prevent procedural performance problems. Notwithstanding severe visual acuity problems, most accommodation issues can be addressed by corrective lenses. Unfortunately, many practitioners have lenses made for either driving, or reading, not for the proper procedural distance of laryngoscopy. The proper procedural distance for a given practitioner is between their arm held at full extension, and the arm flexed at 90 degrees. For most practitioners this is about 14 to 16 inches (35−40 cm). Corrective lenses become a valuable aid to DL in most practitioners by their mid- to late-forties.

What Factors Contribute to Difficult Laryngoscopy and How Reliable Is Prediction?

Difficult laryngoscopy can result from two different issues: (1) problems with landmark recognition and (2) mechanical problems that prevent laryngeal exposure.

Landmark recognition is much more difficult in the presence of blood, secretions, vomitus, or distorted anatomy from a myriad of causes, including burns, edema, and other pathology. Successful laryngoscopy hinges on recognizing the epiglottis and structures of the laryngeal inlet, in addition to the glottic opening and vocal cords. The epiglottis has a mucosal appearance that is very similar to the posterior hypopharynx even without the additional challenges of fluids, vomitus, or distorted anatomy. Fluids from the oropharynx and hypopharynx will collect above the epiglottis when a patient is positioned in a supine position with poor muscular tone (or after the use of muscle relaxants). This can easily cause epiglottis edge recognition failure as the blade is inserted. Elevation of the epiglottis out of the fluids by proper jaw distraction during the first phase of laryngoscopy, which is, in turn, a function of proper head and neck position, and avoidance of overextension may help. Because fluids are often present in the airway, it is appropriate to have a Yankauer suction immediately available.