Michael F. Murphy
Tobias D. Barker
Robert E. Schneider
Laryngoscopy and Orotracheal Intubation
Direct laryngoscopy is the centerpiece of orotracheal intubation. Laryngoscopy is a learned skill, and when it is performed properly, it provides optimal exposure of the glottic opening, facilitating endotracheal intubation. Laryngoscopy is a multifaceted procedure that requires both dexterity and creativity to align the oral, pharyngeal, and laryngeal axes of the airway so that the laryngoscopist is provided the best possible view of the glottis.
Although there are many different types of laryngoscopic blades, they are essentially either straight or curved. Typically, the straight blades are intended to pick up the epiglottis to optimize visualization of the glottic opening. The curved blades are used to negotiate around the base of the tongue to make contact with the hyoepiglottic ligament. Depressing this ligament with the blunt (and usually beaded tip) of a curved blade produces elevation of the epiglottis and exposure of the glottis. Both types of blades can be used either way, although the best success rates are achieved when they are used as intended. Airway managers need to be familiar with both techniques so if one fails the other can be used.
A best attempt at laryngoscopy has six components: (a) performance by a reasonably experienced laryngoscopist, (b) no significant muscle tone (paralysis), (c) optimal positioning of the airway (e.g., sniff position), (d) the use of external laryngeal manipulation, (e) appropriate length of blade, and (f) type of blade. With this definition and no other confounding considerations, the optimal attempt at laryngoscopy and intubation may be achieved on the first attempt and should take no more than three attempts. Because there are different techniques of laryngoscopy, the laryngoscopist needs to choose one method that works best, and use or practice it often, although not to the exclusion of the others.
Anatomy of Intubation
To appreciate the intricacies of laryngoscopy, one must first understand the anatomy of the upper airway. The anatomy of the upper airway, including the larynx, is described in Chapter 4. In the larynx, the vocal cords, which define the glottic opening, lie at the midportion of the thyroid cartilage, and are inferior and posterior to the flexible epiglottis. During laryngoscopy, these constant relationships serve as important anatomical landmarks. When in trouble, one must find the epiglottis because it leads to the cords. There will be occasions during routine or difficult laryngoscopy when the esophagus is exposed and mistaken for the vocal cords. Unless one has a landmark or consistent reference point to confirm the airway anatomically, esophageal intubation may result, or intubation may be unsuccessful. Whenever one is uncertain whether the visualized opening is the glottis or the esophagus, the epiglottis must be found. Once identified, the tip of the epiglottis can usually be elevated with either the straight or the curved blade exposing the cords and the arytenoid cartilages, allowing confident placement of the endotracheal tube (ETT) into the airway.
The single greatest obstacle to successful laryngoscopy is the tongue. To the laryngoscopist, the tongue is the enemy, and the epiglottis is a friend. Anatomically, the base of the tongue may block access to the glottic opening. When the tongue is large in relation to the oral cavity (Mallampati Class III or IV), it can inhibit adequate exposure of the glottic aperture. For this reason, preintubation assessment of the patient's airway is essential. In the mnemonic LEMON, discussed in Chapter 7, the M stands for Mallampati, serving as a reminder to examine the oral cavity to assess the relative size of the tongue in relationship to the oropharynx and the mandibular space. The laryngoscope blade is the tool that controls and maneuvers the tongue. In general, the larger the tongue, the wider the blade (i.e., no. 3 or 4) that should be selected. Fundamental to successful laryngoscopy is the selection of a blade, curved or straight, that will be wide and long enough to capture the tongue at the initiation of laryngoscopy, sweep it leftward out of the visual field, and permit direct visualization of the airway.
Laryngoscope Blades: History and Application
There are two fundamental laryngoscope blade designs, and practitioners typically have preferences for one or the other, even though it is essential that airway managers have facility with both.
Although orotracheal intubation employing a laryngoscope blade was initially described in the late 19th century, it became popularized in the early 20th century by Sir Ivan Magill, who used a semicircular straight blade modified from the ear, nose, and throat surgeon's anterior commissure laryngoscope. This “Magill blade” was inserted at the right corner of the mouth, taking advantage of the fact that the distance from the molars to the glottis was less than the distance from the incisors to the glottis, a factor that improved the airway manager's view of the vocal cords. The tip of the blade picked up the epiglottis, enhancing the view of the glottis. An uncuffed, blunt-tipped, gum elastic ETT was then inserted down the semicircular flange of the blade through the vocal cords and into the trachea. Most of these patients were breathing spontaneously (usually on ether anesthesia), although if positive-pressure ventilation was needed, as it commonly was after the introduction of curare and succinylcholine in the 1940s, oil-soaked gauze was packed around the ETT. This technique became known as the “paraglossal” or “retromolar” technique and remained the standard technique until the 1940s when balloons were applied to ETTs to permit positive-pressure ventilation with the use of neuromuscular blockade. Even today, moving the blade from the midline to the paraglossal position may rapidly convert an intubation failure to a success, particularly if an endotracheal tube introducer, such as an Eschmann introducer (EI), is used. It is a maneuver that may improve the laryngeal view so substantially that every airway manager ought to be aware of it.
Modifications of the Magill blade include other straight blade variants, such as the Miller, Wisconsin, Phillips, Henderson, Guedel, and others. A common feature to most of these blades is that the tip is fairly sharp, as opposed to the curved blade where the tip is squared off and blunt to minimize trauma in the vallecula as it is advanced to depress the hyoepiglottic ligament to flip the epiglottis up to enhance glottic exposure.
The addition of bulky rubber balloons to rubber ETTs in the 1940s hindered or even made impossible their passage through the flange of the Magill blade. To get around this problem, Macintosh invented the curved blade in 1943. This blade was designed to control the tongue and sweep it to the left side of the mouth, creating sufficient room to pass the bulky tube/balloon combination. By the late 1940s, Macintosh tired of his design and reverted to the Magill blade, having invented the intubating stylet (gum elastic bougie or EI) to get around the problem. Macintosh inserted the EI down the flange of the paraglossally inserted Magill blade into the trachea, and then moved the blade to the center of the mouth, guiding the ETT into the trachea over the EI.
Techniques of Laryngoscopy
Preparation and Assistance
The decision to intubate implies that the airway manager has formulated a primary plan and backup plans should the primary plan fail. The primary plan is generally called “Plan A,” whereas the backup plans are called “Plan B” and “Plan C.” Plan A is almost always orotracheal intubation employing a laryngoscope.
Before embarking on the intubation attempt, the airway manager must ensure that the following are available:
· All of the equipment and medications needed for Plans A, B, and C
· Trained assistance
· Adequate suction
The assistant needs to be positioned on the right side of the patient and be trained and prepared to
· Pass equipment as needed to the airway manager.
· Hold the head in a position as stipulated.
· Apply Sellick's maneuver and laryngeal manipulation.
· Hold open the corner of the mouth during intubation.
· Remain in position until excused by the airway manager.
Fundamentals of Laryngoscopy
Laryngoscopy is two-handed procedure: the airway manager holds the laryngoscope in the left hand, and the right hand is placed under the patient's occiput to tilt the head back to open the mouth and lift and move the head during the laryngoscopy in an attempt to optimally visualize the glottis. Once the airway manager has the “best view” of the larynx, the assistant is asked to hold the head in that position with the left hand.
Positioning the Airway
Laryngoscopy will be more successful if the laryngoscopist assumes or creates a comfortable intubating position that allows inline visualization of the airway. This can be accomplished by adjusting either the height of the patient or the height of the intubator (stool, kneeling) to bring the airway into the laryngoscopist's central field of vision. Uncomfortable, contorted body positions lead to fatigue and unnecessarily complicate laryngoscopy.
Before placing the laryngoscope into the patient's mouth, the sniffing position is created by placing a pillow, folded towel, or sheet under the patient's head to facilitate slight forward flexion of the lower cervical spine on the chest and extension of the head on the neck (“sniffing the morning air” or “sipping English tea”; the “flex/extend” position) (Fig. 6-1). The “flex/flex” position provides better laryngeal exposure for some patients, whereas for others (e.g., the morbidly obese) the “extend/extend” position is better. Although there has been some controversy as to whether the sniffing position is best, it is generally accepted that this is the best starting position. The laryngoscopist's right-hand positioning of the head permits one to rapidly achieve the best position for intubation.
In the trauma victim, where inline stabilization of the cervical spine is recommended, or in patients with decreased cervical spine mobility, flexion of the lower cervical spine onto the chest and extension of the head on the neck may be impossible or inappropriate, thus making laryngoscopy more difficult. Patients with advanced cervical arthritis may have markedly reduced neck motion, which may also confound laryngoscopy.
Opening the Mouth
Once the optimal position for laryngoscopy has been achieved, the mouth is opened by tilting the head back with the right hand or by using the fingers of the right hand to “scissor” the mouth open. This latter maneuver is awkward because the scissoring fingers obstruct access to the right side of the mouth by the blade. In the event that mouth opening is limited, or the chest obstructs the handle preventing insertion, it may be necessary to remove the blade from the handle, insert the blade into the mouth, and then reattach the handle.
Handling the Laryngoscope
The laryngoscope handle should always be grasped in the left hand. Although laryngoscope manufacturers can supply devices for use with the right hand, they are difficult to acquire and both left- and right-handed care providers are advised to learn to hold the laryngoscope handle in their left hands.
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Figure 6-1 • A: Anatomical neutral position. The oral axis (OA), pharyngeal axis (PA), and laryngeal axis (LA) are at greater angles to one another. B: Head, still in neutral position, has been lifted by a pillow flexing the lower cervical spine and aligning the PA and LA. C: The head has been extended on the cervical spine, aligning the OA with the PA and LA, creating the optimum sniffing position for intubation. |
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Figure 6-2 • Laryngoscopy. A: Recommended grip of the laryngoscope. B: Technique of achieving greater glottic exposure. Note how the end of the laryngoscope handle is directed at approximately 45 degrees, and lift is applied longitudinally. C: Absence of the rocking motion will prevent dental injury and trauma. |
To minimize trauma to airway structures, it is advisable during the blade insertion stage of laryngoscopy to hold the handle with the fingertips to maximize maneuverability and tactile fidelity, not clenched in the palm of the hand (“death grip”) (Fig. 6-2). Once the tip of the laryngoscope blade is positioned where the operator wants it, the laryngoscope handle can be grasped using any familiar technique, including the death grip, as one applies elevation force to optimize laryngeal exposure. However, the expenditure of precious muscle strength during a phase of laryngoscopy where strength is not needed only serves to sap power from when it may be needed most as one tries to elevate the tongue and epiglottis to reveal the glottic opening.
If using a straight blade, the volar pad of the thumb may be positioned on the proximal end of the blade at the connection with the handle to facilitate advancement, particularly if the “insert blindly and withdraw technique” is being used.
Insertion of the Blade
There are two methods of inserting the laryngoscope blade into the mouth and over the tongue: the “look as you go” technique and the “insert blindly and withdraw technique.” The former technique is the one usually employed with both straight and curved blades; the latter only with straight blades, and most often in infants.
Curved blades are intended to be advanced into the vallecula and depress the hyoepiglottic ligament to flip the epiglottis forward. This is crucial to the optimal visualization of the glottis with this blade, and failure to do so is a fundamental factor leading to failure. The airway manager advances the curved blade over the tongue under direct vision until the tip of the epiglottis is visualized. At this point, the blade is gently “levered home” into the vallecula. Only after the tip of the blade is pressed firmly into vallecula does one “lift” the handle and blade to expose the glottis. Incomplete insertion may cause the posterior aspect of the tongue to “squeeze” out beneath the blade and force the epiglottis down over the glottis creating a grade 3B view (see Chapter 7).
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Figure 6-3 • A: Oral Cavity. B: Initial anatomical relationship of the flange of the blade with the lingual surface of the molar teeth. Note there is no tongue between the flange of the blade and the teeth. |
Straight blades are intended to pick up the epiglottis whether inserted blindly or under direct vision (“look as you go” technique). Although the tip of the straight blade may be inserted into the vallecula, caution is advised if the blade has a sharp tip.
The blind insertion technique is generally faster than the look as you go technique. It also has the advantage of one knowing that the tip of the laryngoscope is beyond the glottis in the esophagus, eliminating the uncertainty that many infrequent intubators suffer when they intubate and cannot figure out “Am I too deep or too shallow?”
If one elects to use a blind insertion technique, there are two stages to the technique: a nonvisual insertion stage and a visual withdrawal stage. In the first stage (nonvisual) of this technique, the laryngoscope blade is fully inserted blindly, but gently, into the esophagus. Assuming the patient is totally paralyzed with maximum mandibular mobility, the laryngoscope blade is placed into the right side of the patient's mouth alongside the lingual surface of the right mandibular molar teeth (Fig. 6-3). This is an extremely important initial anatomical relationship in controlling the tongue. The laryngoscopist must be certain there is no tongue between the flanged surface of the blade and the lingual surface of the mandibular molar teeth before beginning laryngoscopy. If any tongue is seen, the laryngoscope should be removed and then replaced in the correct starting position. Failure to establish this starting position will compromise control of the tongue, potentially obstruct visualization of the glottic opening, and hinder passage of the ETT (Fig. 6-4). Blade insertion is generally much easier with the patient in the sniffing position rather than the neutral position. In the latter instance (most trauma patients), the laryngoscope blade must hug the anterior surface of the tongue as the blade compresses the tongue into the floor of the mouth and simultaneously opens the mandible and atraumatically advances through the oropharynx, posterior pharynx, and into the esophagus. This procedure is gentle, but requires some muscle power. If more space is required to negotiate the posterior pharyngeal turn, it must be generated by further movement of the mandible as opposed to the neck.
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Figure 6-4 • Tongue Control During Laryngoscopy. A and B: Poor visualization of the cords due to incorrect positioning of the blade. Note how the tongue folds over the blade and obscures the view. C: Correct positioning of the blade to control and move the tongue to the left, providing an optimal view for intubation. |
Once the blade has been correctly positioned adjacent to the right mandibular molar teeth, its entire length is passed blindly and atraumatically into the patient's esophagus, traversing the base of the tongue, passing posterior to the epiglottis and cords, anterior to the posterior pharyngeal wall, and finally moving superiorly and anteriorly through the cervical esophagus into the proximal body of the esophagus. Active visualization of the posterior pharyngeal or laryngeal anatomy is neither possible nor required during this initial maneuver. As mentioned previously, the esophageal insertion is done completely by feel, with gentle pressure exerted by the volar pads of the fingers and thumb, allowing the laryngoscopist to feel the advancing tip of the laryngoscopic blade. Any perception of resistance during this maneuver requires immediate cessation of advancement, slight withdrawal and realignment superiorly, and then reinsertion. The tip of the advancing blade should move toward the midline during this insertion. The laryngoscopist can be assured that the application of cricoid pressure may need to be eased slightly to effect a complete atraumatic insertion.
As mentioned previously, with this initial position established, the cords will always be proximal to the tip of the laryngoscope blade, never distal (Fig. 6-5).
The second stage is totally visual. Under direct vision, the blade is slowly withdrawn from the esophagus to initially expose the glottis, the epiglottis (which can be picked up with the tip of either blade, providing maximum laryngeal exposure for successful intubation), and the base of the tongue (Fig. 6-6). It may require transient forearm muscle power to further elevate the tongue into the mandibular space just before intubation to achieve maximum glottic exposure.
Bimanual Laryngoscopy
Cormack and Lehane quantified the extent to which one is able to visualize the larynx, epiglottis, and upper airway during laryngoscopy (Fig. 6-7). Grades 1 and 2 are usually associated with low laryngoscopic failure rates, whereas grades 3 and 4 usually have higher failure rates. Grade 3 has been further subdivided into grade 3A, where the epiglottis sits up, and grade 3B, where it remains flopped down over the glottis.
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Figure 6-5 • A: The initial starting position for the visual phase of laryngoscopy. B: Note that the blade is in the esophagus and the blade/handle junction is at the patient's teeth. Note the position of the cords proximal to the tip of the blade. |
If the laryngoscopic view is less than adequate, reaching around to manipulate the larynx with the free right hand to apply firm backward, upward, and rightward pressure on the thyroid cartilage will most often improve the laryngeal view one full grade, producing maximum glottic exposure. This maneuver, which is distinct from cricoid pressure (Sellick's maneuver), is called the BURP maneuver (Back ward, Up ward, Right ward Pressure) or optimum external laryngeal manipulation (Fig. 6-8). Although this maneuver will often lead to improved visualization, the operator should always individualize the movement of the thyroid cartilage to optimize the laryngoscopic view.
Once the vocal cords are exposed and positioned optimally by the laryngoscopist, the assistant providing cricoid pressure with the right long finger and thumb can use the free right index finger to maintain this optimum view, and without releasing cricoid pressure, can perform a combined maneuver to give both Sellick's maneuver and BURP. This frees the laryngoscopist's right hand to insert the ETT.
Intubating the Trachea
Once the glottis has been identified, it is important that the laryngoscopist not lose sight of the target. The assistant, standing at the patient's right side applying Sellick's maneuver or Sellick-BURP with the right hand, should pull open the right side of the patient's mouth with the left index finger, providing generous access to the oropharynx and, most importantly, providing room for unimpeded passage of the ETT (Fig. 6-9). The ETT should be passed from the right side of the patient's mouth and must not be passed down the flange of the blade, if one is using a straight blade. If the ETT is mistakenly passed down the flange of the blade, it can become trapped, preventing advancement, or the cuff can be lacerated. Entering from the right side of the patient's mouth prevents the loss of the target in the laryngoscopist's visual field.
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Figure 6-6 • Exposure of The Cords. A: Initial withdrawal of the laryngoscope will usually expose the cords. If not, further withdrawal of the laryngoscope will disclose the epiglottis (B), which can be picked up and elevated (C), disclosing the glottic aperture. |
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Figure 6-7 • Cormack-Lehane Laryngoscopic Grading System. Grade 1 is visualization of the entire glottic aperture. Grade 2 is visualization of just the arytenoid cartilages or the posterior portion of the glottic aperture. Grade 3 is visualization of only the epiglottis. Grade 4 is visualization of only the tongue or the tongue and soft palate. |
As the ETT is initially passed into the right side of the patient's mouth, the bevel of the tube should lie in a horizontal position. The tube initially contacts the hard palate and then sweeps the soft palate as it is advanced toward the glottic opening occupying a position in the right peripheral field of vision. At the glottic opening, the bevel should be simultaneously rotated counterclockwise 90 degrees from a horizontal tube tip orientation to a vertical tube tip orientation so the narrowest dimension of the tube tip enters the glottis in alignment with the vocal cords (Fig. 6-10).
The angle that the stylet used in the ETT is bent is an individualized decision. It has, however, been shown to have an improved chance of passing beyond the glottis if the angle is less than 35 degrees. Following passage through the cords, the laryngoscope and the stylet are removed, and the balloon is inflated.
Endotracheal Tube Introducers
EIs are custom designed for Cormack Lehane grade 2 and 3 views. They are a fundamental piece of airway management equipment that must be part of every airway manager's skill set. As described previously, the EI employs a Seldinger-type technique. Crucial to success is the continuation of laryngoscopy during passage of the ETT over the EI.
EIs are ordinarily plastic, 60 to 70 cm in length, and incorporate a 30-degree deflection of the distal tip. The tip deflection enhances the anterior movement of the distal tip underneath the epiglottis, maximizing the chance it will pass into the glottis and hence the trachea, and permits the tactile appreciation of tracheal rings once placed in the trachea. Seventy-centimeter devices are easier to use than those 60 cm in length. A standard ETT is 30 cm in length, so 60 cm is exactly twice the length of an ETT; the added 10 cm of the 70-cm device facilitates grasping the proximal end of the EI as the ETT is advanced into the trachea. One manufacturer supplies a device with a hollow lumen to permit some degree of oxygenation in the event tube passage over the EI fails (Frova by Cook Critical Care, Bloomington, IN). Some EIs are reusable, whereas others are intended as single-use devices.
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Figure 6-8 • A: Relatively anteriorly placed larynx. B: BURP maneuver on the thyroid cartilage. C: BURP maneuver improves the laryngeal view for intubation. |
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Figure 6-9 • Retraction of the corner of the mouth by an assistant's index finger will provide ample room for unobstructed passage of the endotracheal tube. |
The EIs are labeled in centimeters, depicting the distance from the tip. The print on the EI is aligned on the same side of the EI as the tip deflection. Positioning the 25-cm mark of the EI at the patient's lip correlates with the tip of the EI at midtrachea. It is important to keep the writing and hence the deflected tip up (anterior) as the ETT is passed over the EI to minimize the chance of forcing the ETT posteriorly in the trachea, risking a posterior tracheal perforation.
Technique of Passing the EI
When using the EI, some laryngeal structure (epiglottis or better—grade 2 or 3) must be visible. Under direct vision, the EI is inserted behind the epiglottis, and an attempt is made to insert the tip through the glottis into the trachea. In a grade 2 view, the EI may be seen to enter the glottis. In a grade 3 view, the tip of the EI will not be seen to enter the glottis or trachea. Once in the trachea, the tip can often transmit a subtle click, click, click sensation generated by the tracheal rings as the EI is moved gently in and out of the airway. Feeling this sensation enhances your confidence that the EI is in the trachea; failing to sense it does not mean that the EI is not in the trachea. The tongue or other airway structures contacting the shaft of the EI may insulate against the transmission of the corrugated vibrations. In the case where tracheal rings cannot be felt, the EI should be gently advanced. If it is in the trachea, it will “hold up” at some point. Hold up will not occur if the EI is in the esophagus. In the event holdup occurs, withdraw the EI to 25 cm at the lips before advancing the ETT over the EI.
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Figure 6-10 • The Endotracheal Tube is Rotated 90 Degrees Counterclockwise. (B) as it is passed through the cords, changing the initial horizontal (widest) axis of the bevel (A) to the vertical (narrowest) axis (C). |
Failure of the ETT to pass easily over the EI into the trachea is most often due to the failure to maintain a “best laryngoscopic view” during the ETT insertion. Keeping the laryngoscope in place minimizes the angle the ETT/EI combination must negotiate and enhances the chance of successfully intubating the trachea.
As the ETT is passed over the EI, a gentle clockwise or counterclockwise twist as the bevel of the ETT reaches the glottis enhances passage. If the ETT gets hung up, rotate the tube 90 degrees, first to the right and then to the left. The tip of the ETT may be caught on the posterior commissure of the glottis, the anterior commissure of the cords, either cord, or the cricoid cartilage, although it is impossible to know the exact location. A similar experience may occur when the EI is passed. The possibilities and remedies are identical.
Once the ETT is in place, the intubating EI is removed, and tube position is confirmed.
Confirming Intubation of the Trachea
Once the ETT has been placed, it is imperative to confirm that it is in the patient's trachea. Traditionally, one of the “gold standards” has been the direct visualization of the ETT passing through the vocal cords, but even this assertion has proven fallible. Probably the only “gold standard” is visualizing tracheal rings on fiberoptic bronchoscopy. The current standard is the detection of end-tidal carbon dioxide (CO2), most commonly in emergency medicine, emergency medical services and hospital wards, and intensive care units using the colorimetric capnometer, which changes from purple to yellow in the presence of exhaled CO2, or capnography in the operating room, where the presence of an appropriate waveform confirms tracheal placement.
When using a colorimetric end-tidal CO2 detector, the color will quickly change from purple (poor) to yellow (yes). This color change should occur within one or two breaths, but in certain circumstances it may be delayed for up to six breaths. If the color change to yellow is not immediate, one has to be suspicious that the ETT is either in the esophagus or above the cords, rather than being properly positioned in the trachea. A color change to tan rather than to bright yellow may also indicate a supraglottic or esophageal location of the ETT tip. In this circumstance, several options are available to confirm the anatomical location of the tube: the laryngoscopy may be repeated to confirm that the tube is indeed properly positioned through the cords, a new colorimetric device may be tried, or the patient may be extubated and reintubated. If any doubt remains, the tube should be assumed to be in the esophagus.
In those clinical circumstances where CO2 is not produced (e.g., prolonged cardiac arrest), the colorimetric detectors are of limited value and esophageal detecting devices (EDDs) may be used to confirm appropriate tube placement. There are two types of esophageal detecting devices: the piston syringe device and the self-inflating bulb device. Studies have shown that the sensitivity of the self-inflating bulb is greater than the piston syringe. The principle behind these devices relates to the anatomical differences between the trachea and the esophagus. The trachea is composed of anteriorly positioned cartilaginous rings that prevent the collapse of the airway into the ETT when the piston is aspirated or the compressed bulb is released and allowed to reinflate. Because the esophagus is a circumferentially muscular structure without any bony or cartilaginous support, placement of the ETT into the esophagus and aspiration of the syringe or release of the self-inflated bulb will invaginate the esophageal mucosa into the tube and prevent easy removal of the piston or rapid reinflation of the bulb. These devices are quite sensitive and specific, but again must be used in conjunction with other techniques to confirm proper placement of the ETT into the trachea.
Auscultation of the left supraclavicular area, left axilla, left chest, right chest, and epigastrium, respectively, are additive to end-tidal CO2 and EDD confirmation techniques. The left side of the chest is preferentially auscultated first to confirm that a right mainstem intubation has not occurred. Fogging (condensation) of the ETT is a completely unreliable method of confirming tracheal intubation and should not be relied on. With the exception of bronchoscopic confirmation, none of these techniques taken alone guarantee proper placement of the ETT in the trachea. Thus, it is recommended that they all be done, especially in the arrested patient.
Chest x-rays are used primarily to assess for mainstem intubation and to evaluate tube position within the trachea, not to determine whether the ETT is in the trachea.
Failed Laryngoscopy and Intubation
When tracheal intubation is unsuccessful, the patient should be ventilated with a bag and mask and high-flow oxygen if the saturations are below 90%. During this reoxygenation time, the laryngoscopist should systematically analyze the likely causes of the failure (Box 6-1). It makes no sense to attempt a second laryngoscopy without changing something in the procedure to improve chances for success. The following questions should be addressed:
· Is the patient in the optimum position for laryngoscopy and intubation? If the patient was placed in the sniffing position initially and the larynx still appeared quite anterior, reducing the degree of head extension could be helpful. In addition, it may even help to elevate and flex the patient's head with the laryngoscopist's free right hand (actually flex both the head and the neck) while performing laryngoscopy to create a better view of a true anterior airway.
· Would a different blade provide a better view? If the initial attempt at laryngoscopy was done with a curved blade, it may be advisable to change to a straight blade and vice versa. Alternatively, a different size blade of either type might be helpful.
· Is the patient adequately paralyzed? Laryngoscopy may have been attempted too soon after administering succinylcholine, or an inadequate dose of succinylcholine may have been administered. If the total time of paralysis has been such that the effect of succinylcholine is dissipating, then administration of a second full paralyzing dose of succinylcholine is advisable. If this occurs, atropine must be available to treat potential bradycardia that occasionally accompanies repeat dosing of succinylcholine. Appropriate paralysis can improve the view of laryngoscopy one full grade.
· Would external laryngeal manipulation (BURP) be helpful? Most often, BURP improves the laryngeal view by one full grade.
· Is a more experienced laryngoscopist available? If so, a call for help may be in order.
BOX 6-1 Laryngoscopy: Common Errors Associated with Failed Attempts
· No tongue should be visible on the right side of the blade. If there is, remove the blade and reinsert it.
· Once the glottis is visualized using the left arm and hand, keep it in view! Do not relax the left hand/arm when you pick up the endotracheal tube with the right hand/arm.
· Keep your wing up. Although it is more comfortable to rest your elbow on the pillow or stretcher, once you have done that, all that you can do with the laryngoscope is lever it, pushing the target up and away from you.
Evidence
1. What is the best positioning of the airway for laryngoscopy? Cormack and Lehane (1) devised the most widely accepted system of categorizing the view of the larynx achieved with an orally placed laryngoscope. More recently, Levitan et al. (2) devised a scoring system to quantitate the percentage of glottic opening visible, which is becoming used more frequently in the literature. The sniffing position (head extension, neck flexion) has been widely accepted as the optimum position for orotracheal intubation, although Adnet et al. recently challenged this dogma, suggesting that simple extension (head extension, neck extension) may be superior (3,4). For difficult intubations, there is even literature to support simple flexion (head flexion, neck flexion) to optimize visualization (5,6). Although the question of optimal head positioning remains, it is likely that it will vary from patient to patient. This highlights the importance of a two-handed technique for intubation, allowing for individualized adjustments during laryngoscopy.
2. Is thyroid cartilage manipulation during laryngoscopy really necessary? It has clearly been shown that external laryngeal manipulation, one example of which is BURP, improves laryngeal view grade by one full grade, on average (7,8,9). In addition, one recent study demonstrated the importance of operator-directed laryngeal manipulation (as opposed to assistant-directed manipulation) in maximizing visualization of the glottic structures (10). The importance of laryngoscopy being a bimanual technique is emphasized regardless of which direction the thyroid cartilage is displaced.
3. Are EIs truly helpful? The literature clearly supports the use of EIs to enhance success rates of intubation, particularly with grade 3 views (11,12,13,14,15). In one study, the success rate improved from 66% to 96% after two attempts (14). Rotation of the tube, usually 90 degrees counterclockwise, enhances ETT insertion success. In addition, one study has shown a negative effect of Sellick's maneuver on the success of ETT passage over the EI (16). Pathogenic bacteria may colonize both the Eschmann (Portex) variety of EI and the plastic container it is housed in, emphasizing the importance of sterilizing the device after each use (17). Although rare, bronchial perforation has been reported with the device (18).
4. Does it matter which laryngoscopic blade I use? It is generally believed that one's choice of a laryngoscope blade and the technique used to facilitate intubation is best guided by personal choice and experience (3,19,20). The literature suggests that straight blades improve laryngoscopic view (increased exposure of the vocal cords), whereas curved blades provide better intubating conditions (more room to maneuver) (20). The introduction of wider blades (e.g., Grandview) and use of intubating stylets improves intubation success rates with the straight-blade technique (14). Regardless of the blade used, once visualization is obtained, the degree of stylet induced ETT angulation can help or hinder passage through the larynx. One recent study demonstrated the optimal bend to be a 25- to 35-degree angle (21).
A modern Macintosh-type laryngoscope with a hinged tip that flexes when a lever on the handle is depressed was introduced by McCoy and Mirakhur in 1993 (22). The mechanism of displacement of the tongue and elevation of the epiglottis is similar to the Macintosh laryngoscope, in that the tip of the laryngoscope is inserted into the vallecula and the epiglottis is elevated indirectly by depressing the hyoepiglottic ligament. There have been many reports of conversion of grade 3 views to grade 1 or 2 (23). However, there have also been reports of failures (24).
5. What are the various methods for confirming correct ETT placement? Visualization of the ETT entering the larynx provides a reliable method of verifying correct position of the tube. Fiberoptic bronchoscopy remains the gold standard for verifying correct ETT placement in adults and pediatric patients by permitting the direct visualization of tracheal rings. This technique has also been used in the setting of emergency airway management (25,26,27). Auscultation of the chest for breath sounds and of the epigastrium for absence of air entry into the stomach and observation of chest motion during ventilation are common but notoriously inaccurate methods of ascertaining proper ETT placement. CO2 detection and EDDs have become the standards of care to verify correct placement of the ETT in the trachea, although both techniques have shortcomings (28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43). As might be expected, CO2 detection techniques tend to be less accurate in identifying correct placement of the ETT in patients with cardiac arrest, with reported false-negative rates (CO2 not detected despite the tube being in the trachea) as high as 30% to 35% (32). In nonarrested patients, CO2 detection is highly reliable, indicating correct placement 99% to 100% of the time (28,31,37). Soft drinks in the stomach containing CO2 may mimic the exhaled CO2 from the lungs for a few breaths, the so-called Cola complication; this confounding result ought not to persist beyond six breaths (42). The correct endotracheal placement of the tube can be evaluated by an EDD that consists of a self-inflating suction bulb or syringe and an attached adapter to fit it to a standard ETT connector. The collapsed bulb or syringe rapidly fills with air if the ETT is in the trachea; it does not inflate if the tube is in the collapsed esophagus with a specificity of about 99% (34,43). Lighted stylets have also been used to verify tracheal placement (44). In general, none of these techniques alone guarantee correct placement, and as many of them as possible should be used in every case.
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