Structure

The larynx is composed of one bone (hyoid) and eleven cartilages (the single thyroid, cricoid, and epiglottic cartilages and the paired arytenoid, corniculate, cuneiform, and triticea cartilages). These cartilages are suspended by ligaments from the base of the skull. The body of the cricoid cartilage articulates posteriorly with the inferior cornu of the thyroid cartilage. The paired triangular arytenoid cartilages rest on top of, and articulate with, the superoposterior aspect of the cricoid cartilage. The arytenoid cartilages are protected by the thyroid cartilage (Fig. 12-8). The triticeal cartilages are rounded nodules of cartilage, approximately the size of a pea in adults, located in the margins of the lateral thyrohyoid ligament.

FIGURE 12-8 Laryngeal cartilages. The natural positions of the laryngeal cartilages are presented on the left, with the individual cartilages separated on the right.

(Reprinted by permission from Fink BR, Demarest RJ. Laryngeal biomechanics. Cambridge, Mass.: Harvard University Press, © 1978 by the President and Fellows of Harvard College.)

Tissue folds and muscles cover these cartilages. In contrast to adults, but comparable to most mammals, the cartilaginous glottis accounts for 60% to 75% of the length of the vocal folds in children younger than 2 years of age.¹⁰ Contraction of the intrinsic laryngeal muscles alters the position and configuration of these tissue folds, thus influencing laryngeal function during respiration, forced voluntary glottic closure (Valsalva maneuver), reflex laryngospasm, swallowing, and phonation (Fig. 12-9).

FIGURE 12-9 Photograph (A) and schematic diagram (B) of the larynx of a premature infant.

The laryngeal tissue folds consist of the following:

Histology

The highly vascular mucosa of the mouth is continuous with that of the larynx and trachea. This mucosa consists of squamous, stratified, and pseudostratified ciliated epithelium. The vocal cords are covered with stratified epithelium. The mucosa and submucosa are rich in lymphatic vessels and seromucus-secreting glands, which lubricate the laryngeal folds. The submucosa consists of loose fibrous stroma; therefore, the mucosa is loosely adherent to the underlying structures in most areas. However, the submucosa is scant on the laryngeal surface of the epiglottis and the vocal cords, so the mucosa is tightly adherent in these areas.^12,13 Most inflammatory processes of the airway above the level of the vocal cords are limited by the barrier formed by the firm adherence of the mucosa to the vocal cords.¹³ For example, the inflammation of epiglottitis is usually limited to the supraglottic structures, and the loosely adherent mucosa explains the ease with which localized swelling occurs (see Figs. 31-15 and 31-16). In a similar manner, an inflammatory process of the subglottic region (laryngotracheobronchitis) results in significant subglottic edema in the loosely adherent mucosa of the airway below the vocal cords, but it does not usually spread above the level of the vocal cords (see Fig. 31-14, C).¹²

Sensory and Motor Innervation

Two branches of the vagus nerve, the recurrent laryngeal and the superior laryngeal nerves, supply both sensory and motor innervation to the larynx. The superior laryngeal nerve has two branches: the internal branch, which provides sensory innervation to the supraglottic region, and the external branch, which supplies motor innervation to the cricothyroid muscle. The recurrent laryngeal nerve provides sensory innervation to the subglottic larynx and motor innervation to all other laryngeal muscles.^13,14 Local anesthetic agents injected to block the superior laryngeal nerve result in anesthesia of the supraglottic region down to the inferior margin of the epiglottis and motor blockade of the cricothyroid muscle, which causes relaxation of the vocal cords. Translaryngeal injection of local anesthetic through the cricothyroid membrane or a specific recurrent laryngeal nerve block is required for infraglottic and tracheal anesthesia.^15–17

Blood Supply

Laryngeal branches of the superior and inferior thyroid arteries provide the blood supply to the larynx. The recurrent laryngeal nerve and artery lie in close proximity to each other, which accounts for the occasional vocal cord paresis after attempts to control bleeding during thyroidectomy.¹⁸

Inspiration

During inspiration, the larynx is pulled downward (caudad) by the negative intrathoracic pressure generated by the descent of the diaphragm and contraction of the intercostal muscles. Longitudinal stretching of the larynx results, thus increasing the distance between the aryepiglottic and vestibular folds as well as the distance between the vestibular and vocal folds. When the intrinsic muscles within the larynx contract, the arytenoids move laterally and posteriorly (rocking backward and rotating laterally), thereby increasing the interarytenoid distance and separating as well as stretching the paired aryepiglottic, vestibular, and vocal folds. Overall, inspiration enlarges the laryngeal inlet, both longitudinally (like opening a telescope) and laterally, allowing the passage of greater quantities of air through the airway per unit time.

Expiration

At the end of expiration, the larynx reverts to its resting position, with longitudinal shortening of the distance between the aryepiglottic, vestibular, and vocal folds (like closing of a telescope). The arytenoids return simultaneously to their resting position by rotating medially and rocking forward, thus decreasing the interarytenoid distance and reducing the tension on the paired aryepiglottic, vestibular, and vocal folds and causing them to thicken.

Forced Glottic Closure and Laryngospasm

Glottic closure during forced expiration (forced glottic closure or Valsalva maneuver) is voluntary laryngeal closure and is physiologically similar to involuntary laryngeal closure (laryngospasm). Forced glottic closure occurs at several levels. Contraction of the intrinsic laryngeal muscles results in (1) marked reduction in the interarytenoid distance; (2) anterior rocking and medial movement of the arytenoids, causing apposition of the paired vocal, vestibular, and aryepiglottic folds; (3) longitudinal shortening of the larynx that obliterates the space between the aryepiglottic, vestibular, and vocal folds (like complete closing of a telescope). Contraction of an extrinsic laryngeal muscle, the thyrohyoid, pulls the hyoid bone downward (caudad) and the thyroid cartilage upward (cephalad), leading to further closure.^{1,3,4,19–22}

Closure of the larynx during laryngospasm is similar to, but not identical to that described for voluntary forced glottic closure. There are two important differences. First, laryngospasm is accompanied by an inspiratory effort, which longitudinally separates the vocal from the vestibular folds. Second, in contrast to forced glottic closure, neither the thyroarytenoid muscle (an intrinsic muscle of the larynx) nor the thyrohyoid muscle contracts; thus, apposition of the aryepiglottic folds and median thyrohyoid folds is minimal. These two differences allow the upper portion of the larynx to be left partially open during mild laryngospasm, resulting in the hallmark high-pitched inspiratory stridor (see Video 12-1).^1,19 Anterior and upward displacement of the mandible (jaw thrust) longitudinally separates the base of the tongue, the epiglottis, and the aryepiglottic folds from the vocal folds, helping to relieve laryngospasm.²⁰

Swallowing

Glottic closure during swallowing is also similar to that which occurs during forced closure of the glottis. Protection of the glottic opening is achieved primarily by apposition of the laryngeal folds and secondarily by upward (cephalad) movement of the larynx. The upward movement of the larynx brings the thyroid cartilage closer to the hyoid bone, resulting in folding of the epiglottis over the glottic opening.^1,19,21,22 With loss of consciousness or deep sedation, the normal protective mechanism of the larynx may be lost or obtunded, thus predisposing to pulmonary aspiration of pharyngeal contents.

Phonation

Phonation is accomplished by alteration of the angle between the thyroid and cricoid cartilages (the cricothyroid angle) and by medial movement of the arytenoids during expiration.^1,14,23 These movements result in fine alterations in vocal fold tension during movement of air, causing vibration of the vocal folds. Lesions or malfunctions of the vocal folds (e.g., inflammation, papilloma, paresis) therefore affect phonation. Phonation is the only laryngeal function that alters the cricothyroid angle.¹Therefore, despite significant airway obstruction during inspiration, it may still be possible to phonate.

Technique

As previously discussed, because of differences in anatomy, there are differences in techniques for intubating the trachea of infants and children compared with adults.1–4,20–22^,101,116,117 Because of the smaller dimensions of the pediatric airway, there is increased risk of obstruction with trauma to the airway structures. A technique to be avoided is that in which the blade is advanced into the esophagus with laryngeal visualization achieved during withdrawal of the blade. This maneuver may result in laryngeal trauma when the tip of the blade scrapes the arytenoids and aryepiglottic folds.

There are several approaches to exposing the glottis in infants with a Miller blade. One approach consists of advancing the laryngoscope blade under constant vision along the surface of the tongue, placing the tip of the blade directly in the vallecula, and then using this location to pivot or rotate the blade to the right to sweep the tongue to the left and adequately lift the tongue to expose the glottic opening. This technique avoids trauma to the arytenoid cartilages. Lifting the base of the tongue lifts the epiglottis, exposing the glottic opening. If this technique is unsuccessful, the epiglottis may be lifted directly with the tip of the blade (see Video 12-1). Another approach is to insert the Miller blade into the mouth at the right commissure over the lateral bicuspids/incisors (paraglossal approach). The blade is advanced down the right gutter of the mouth, aiming the blade tip toward the midline while sweeping the tongue to the left. Once the blade is under the epiglottis, the epiglottis is lifted with the tip, exposing the glottic aperture. By approaching the mouth over the bicuspids/incisors, dental damage is obviated. This is a particularly effective approach for the infant or child with micrognathia. Whichever approach is used, care must be taken to avoid using the laryngoscope blade as a fulcrum through which pressure is applied to the teeth or alveolar ridge. If there is a substantive risk that pressure will be applied to the teeth, a plastic tooth guard may be applied to cover the teeth at risk (the central incisors of the maxilla).

Optimal positioning for laryngoscopy changes with age. The trachea of older children (≥6 years) and adults is most easily exposed when a folded blanket or pillow is placed beneath the occiput of the head (5 to 10 cm elevation), displacing the cervical spine anteriorly.¹¹⁸ Extension of the head at the atlantooccipital joint produces the classic “sniffing” position.^101,119,120 These movements align three axes: those of the mouth or oral (O), pharynx (P), and trachea (T). Once aligned, these three axes permit direct visualization of laryngeal structures. They also result in improved hypopharyngeal patency.^{32,34,70,78,119,120} Figure 12-14 demonstrates maneuvers for positioning the head during airway management. In infants and younger children, it is usually unnecessary to elevate the head because the occiput is large in proportion to the trunk, resulting in adequate anterior displacement of the cervical spine; head extension at the atlantooccipital joint alone aligns the airway axes. If the occiput is displaced excessively, exposure of the glottis may actually be hindered. In neonates, it is helpful for an assistant to hold the patient’s shoulders flat on the operating room table with the head slightly extended. Some practitioners have adopted the practice of placing a rolled towel under the shoulders of neonates to facilitate tracheal intubation. This technique may be disadvantageous if the laryngoscopist stands but may be advantageous if he or she is seated.

FIGURE 12-14 Correct positioning for ventilation and tracheal intubation. When a patient is lying flat on the bed or operating table (A), the oral (O), pharyngeal (P), and tracheal (T) axes pass through three divergent planes (B). A folded sheet or towel placed under the occiput of the head (C) aligns the P and T axes (D). Extension of the atlantooccipital joint (E) results in alignment of all three axes (F).

The validity of the three-axis theory (alignment of the O, P, and T) to describe the optimal intubating position in adults has been challenged.^121–124 Some authors question the notion that elevation of the occiput improves conditions for visualization of the laryngeal inlet based on evidence from both MRI and clinical investigations.^121,123 However, one MRI study in children with an LMA in place found that slight head extension improved the alignment of the glottic and pharyngeal axes but worsened the alignment of the pharyngeal and laryngeal axes.¹²⁵ In a study of adults, neck extension alone was adequate for visualization of the larynx in most patients, but for obese patients and those with limited neck extension, an optimal intubating position was not determined.¹²¹ Others favor the sniffing position but with varying support for the three-axis theory.^126–132 Even if the tracheas of only a few patients are intubated more easily when placed in the sniffing position compared with simple head extension, the current routine application of the sniffing position appears to be the best clinical practice.

Laryngoscopy can be performed while the child is awake, anesthetized and breathing spontaneously, or anesthetized and paralyzed. Most tracheal intubations in children who are awake are performed in neonates, an approach that is not usually feasible or humane in older awake and uncooperative children. Awake intubation in the neonate is generally well tolerated if it is performed smoothly and rapidly; however, an international consensus group and others have cautioned against this practice unless intravenous (IV) access is not available or there is a life-threatening situation.^133–136 Data suggest that preterm and term infants are better managed with sedation and paralysis to minimize adverse hemodynamic responses.^137–141

Selection of Laryngoscope Blade

A straight blade is generally more suitable for use in infants and young children than a curved blade because it better elevates the base of the tongue to expose the glottic opening. Curved blades are satisfactory in older children. The blade size chosen depends on the age and body mass of the child and the preference of the anesthesiologist. Table 12-1 presents the ranges commonly used.

Endotracheal Tubes

Since 1967, all materials used in the manufacture of ETTs have been subjected to rabbit muscle implantation testing in accordance with the standards promulgated by the Z79 Committee.^141a If the material causes an inflammatory response in the rabbits, it cannot be used in the manufacture of ETTs. This has resulted in the elimination of organometallic constituents, which were used in the manufacture of red rubber ETTs.

Selection of the proper size of an ETT depends on the individual child.¹⁴² The only size requirement for a manufacturer is a standardized inner diameter (ID). The external (outer) diameter (OD) varies among manufacturers, depending on the material from which the ETT is constructed. This diversity in OD mandates checking for proper ETT size and leakage around the tube. An appropriately sized uncuffed ETT may be approximated according to the child’s age and weight (Table 12-2).¹⁴³

TABLE 12-2 Endotracheal Tubes (ETTs) Used in Infants and Children

ID, Inner diameter.

^*In some neonates, a cuffed ETT may not have a leak below 30 cm H₂O, and therefore an uncuffed ETT may be more appropriate.

ETTs one-half mm ID greater or less than the anticipated size should be available because of variability in the size of the airway. Use of the diameter of the terminal phalanx of either the second or fifth digit is unreliable.¹⁴⁴ Children with Down syndrome often require an ETT with a diameter smaller than anticipated.¹⁴⁵ After tracheal intubation and stable cardiorespiratory indices are obtained, a sustained inflation to 20 to 25 cm H₂O (short-term intubation perhaps as high as 35 cm H₂O) should be applied to detect an audible or auscultatory air leak over the glottis. If no leak is detected, the ETT should be exchanged for one with an ID 0.5 mm smaller. An air leak at this pressure is recommended because it is believed to approximate the capillary pressure of the adult tracheal mucosa. If lateral wall pressure exceeds this amount, ischemic damage to the subglottic mucosa may occur.¹⁴⁶ Be aware, however, that if the trachea has been intubated without muscle relaxants, laryngospasm around the ETT may prevent any gas leak and mimic a tight-fitting ETT.¹⁴⁷ If such a situation is suspected, the anesthetic depth should be increased, and an air leak may become evident. Changes in head position may also increase or decrease the leak.¹⁴⁷ These maneuvers are important for making the occasional diagnosis of unrecognized subglottic stenosis (see Fig. 36-3, and Videos 12-1 and 12-5).

Traditional teaching has advocated the use of uncuffed ETTs for children younger than 8 years, because an uncuffed ETT with an air leak exerts minimal pressure on the internal surface of the cricoid cartilage and thus poses potentially less risk for postextubation edema (croup).^143,146,148 An uncuffed ETT also allows insertion of a tube with a larger ID, resulting in less airway resistance, although this holds relevance only for a spontaneously breathing child.¹⁴⁹ However, more recent clinical data and clinical practice have challenged these assumptions^150–158; a number of studies demonstrated no differences in the incidence of postextubation complications after cuffed and uncuffed tubes.^150,155 Cited advantages of cuffed ETTs include decreased numbers of laryngoscopies and intubations to determine the appropriate size for the ETT, reduced subglottic pressure, reduced operating room pollution and costs of anesthetic agents, decreased risk of aspiration, accurate control of carbon dioxide tension (Pco₂), better ability to accurately measure the sophisticated physiologic respiratory functions of modern ventilators, absolute ability to deliver increased airway pressures in children with restrictive lung disease, the ability to control cuff pressure, and no increased risk of postextubation stridor.^{150–156,159–161}

A drawback of cuffed tubes is the greater variability in functional OD compared with uncuffed tubes because of differences in cuff shape, size, and inflation characteristics.¹⁶² In general, if a cuffed ETT is inserted, an ETT with a smaller ID should be selected to compensate for the ETT cuff. One study found a 99% rate of appropriate cuffed tube size selection for full-term infants through children 8 years of age using the following formula¹⁵⁵:

To overcome the shortcomings of the many pediatric cuffed tubes, the MICROCUFF ETT (MICROCUFF, PET, I-MPEDC; MICROCUFF GmbH, Weinheim, Germany, distributed by Kimberly-Clark USA) was designed with a high volume/low pressure cuff that is more distally placed along the shaft of the ETT to better accommodate the anatomy of the airway in infants and children (Fig. 12-15).¹⁶³ The ultrathin polyurethane cuff (10 µm) allows tracheal sealing at low pressures and provides a uniform and complete surface contact with minimal formation of cuff folds.^{157,159,163–166} At 20 cm H₂O inflation pressure, the cuffs have a cross-sectional cuff area of approximately150% of the maximal internal tracheal cross-sectional area. Uninflated, the cuff adds only a minimal amount to the OD of the ETT. Shortened cuffs and the elimination of a Murphy eye allow a more distal position of the cuff, thereby theoretically reducing the risk of pressure being applied to the cricoid ring and adjacent mucosa.¹⁶⁷ The location of the cuff on the shaft of the tube helps to ensure cuff placement below the subglottis, perhaps with the advantage of less risk for endobronchial intubation or intralaryngeal cuff position. An anatomically based depth mark on the surface of the tube helps to guide correct placement.

FIGURE 12-15 The MICROCUFF endotracheal tube (MICROCUFF, PET, I-MPEDC; MICROCUFF GmbH, Weinheim, Germany) (right) is designed with an ultrathin polyurethane (10 µm) high-volume/low-pressure cuff that has a more distal position along the shaft of the tube to better accommodate pediatric anatomy. In contrast to more traditional pediatric cuffed endotracheal tubes (left), the elimination of a Murphy eye allows a more distal position of the upper cuff border. The location of the cuff on the shaft of the tube helps to ensure cuff placement below the subglottis—perhaps with the advantage of less risk for endobronchial intubation or intralaryngeal cuff position. An anatomically based depth mark on the surface of the tube helps to guide correct placement.

An investigation of this specially designed ETT for children used the following guidelines to select cuffed ETT sizes¹⁵⁹:

Use of these formulas resulted in the need to reintubate to change tube size in 1.6% of children (6/500).¹⁵⁹ The incidence of postintubation croup was 0.4% (2/500 children). In a randomized, multicenter study in 2246 young children (mean age, 1.9 years), investigators reported a similar findings for cuffed (MICROCUFF) and uncuffed tubes: postextubation stridor, 4.4% and 4.7%, respectively, and ETT exchange, 2.1% and 30.8%.¹⁶¹ However, in a cost/benefit analysis of the MICROCUFF tube (three to six times that of standard ETTs), the reduction in anesthetic cost offset the cost of the MICROCUFF ETT.¹⁶⁰

As a rule, if a cuffed ETT is chosen, the cuff should be inflated to the minimal pressure that seals the air leak; with the MICROCUFF ETT, this appears to be approximately 10.6 cm H₂O.^{159,161,168,169} This air leak must be reevaluated during the anesthetic procedure if nitrous oxide is used, because the gas may diffuse into the cuff, producing excessive tracheal mucosal pressure.^168–170 In fact, the MICROCUFF ultrathin polyurethane ETT cuff has greater permeability for nitrous oxide than conventional polyvinyl chloride cuffs and therefore may increase the cuff pressure more rapidly than other cuffed tubes. However, with the cuff of the MICROCUFF ETT sealing the air leak at approximately 10 cm H₂O in children, the time interval to reach 25 cm H₂O cuff pressure was greater than with a conventional cuffed ETT.¹⁷¹ Routinely checking cuff pressure or filling the cuff with nitrous oxide is recommended.¹⁷² A pressure relief valve that can be connected to the pilot balloon of a cuffed ETT to limit cuff pressures to 20 cm H₂O when nitrous oxide is used has been described.¹⁷³

Endotracheal Tube Insertion Distance

The length of the trachea (vocal cords to carina) in neonates and children up to 1 year of age varies from 5 to 9 cm.⁴⁰ In most infants 3 months to 1 year of age, if the 10-cm mark of the ETT is placed at the alveolar ridge, the tip of the tube rests above the carina. In preterm and full-term infants, the distance is less. In children 2 years old, 12 cm is usually appropriate. An easy way to remember these lengths is 10 for a newborn, 11 for a 1-year old, and 12 for a 2-year old. After 2 years of age, the correct length of insertion (in centimeters) for oral intubation may be approximated by formulas based on age or weight (Table 12-3)^174–177:

TABLE 12-3 Distance for Insertion of an Oral Endotracheal Tube by Patient Age

Some practitioners suggest using anatomic markers to choose the appropriate depth for the tube in the trachea in neonates.^178,179 An advantage of anatomic measurements is that the infant’s weight may not be available immediately after birth or in sick neonates who present to the emergency department with urgent respiratory or cardiac compromise. One study that used chest radiographs to evaluate final ETT position determined that the length of the foot was as accurate as weight-based formulas to determine the depth of insertion for a nasotracheal tube (44% versus 56% rate of optimal placement, and 83% versus 72% satisfactory placement).¹⁷⁹ Alternatively, the nasal-tragus length (the distance from the base of the nasal septum to the tip of the tragus) or the sternal length (the distance from the suprasternal notch to the tip of the xiphoid process) predicted the depth of insertion of the ETT. Either distance plus 1 cm accurately estimated oral ETT tube insertion distance; either distance plus 2 cm accurately estimated nasotracheal tube insertion distance.¹⁷⁸ Both measurements compared favorably with weight-based formulas when tube position was verified by chest radiography.

After the ETT has been inserted and the first strip of adhesive tape has been applied to secure it, one must observe for symmetry of chest expansion and auscultate for equality of breath sounds in the axillae and apices (not on the anterior chest wall). The anterior chest wall in the child is not used to verify tracheal intubation because breath sounds may reverberate across the precordium in small children, precluding the diagnosis of an endobronchial intubation. A CO₂ monitor confirms intratracheal positioning but does not confirm that the tip of the ETT is not in an endobronchial position. A capnogram that diminishes during the first few breaths suggests an esophageal intubation. Unexpectedly increased airway pressures, persistent desaturation, and asymmetrical chest wall movement all suggest an endobronchial intubation. Visible humidity on the walls of the ETT during expiration also confirms tracheal placement, but the humidity may not be visible in younger infants. It is also important to auscultate over the stomach and to observe for desaturation or cyanosis. Once satisfactory position is achieved, a second strip of tape ensures secure fixation (Fig. 12-16).

FIGURE 12-16 Securing the endotracheal tube (ETT). After insertion of the oral ETT and examination for proper position, the area between the nose and upper lip and both cheeks is coated with tincture of benzoin. A, After the benzoin is dry, tape that has been split up the middle is applied to the cheek, and the ETT is placed at the division of the split tape. B, One half is wrapped circumferentially around the tube, and the other half is applied to the space above the upper lip. C, A second piece of tape is applied in similar fashion from the opposite direction. A nasal ETT may also be secured with this technique.

We have observed a number of children whose ETT moved into a main stem bronchus after initial correct position during repositioning for the surgical procedure; this manifested as a slight but persistent decrease in oxygen saturation (e.g., from 100% to a range of 93% to 95%). Several studies have demonstrated that simple flexion or extension of the neck can move the ETT sufficiently to cause an endobronchial intubation or dislodgement of the tube from the trachea, respectively.^180–182 When a small but persistent change in oxygen saturation is noted, rather than increase the inspired oxygen concentration (Fio₂), one must first investigate the cause and reassess the position of the ETT.¹⁸³

Complications of Tracheal Intubation

Laryngotracheal (Subglottic) Stenosis

Ninety percent of acquired subglottic stenoses are the result of tracheal intubation, particularly prolonged intubation (see Videos 12-1 and 12-2).^201–205 The incidence of subglottic stenosis after prolonged intubation in preterm neonates is reduced because the cricoid cartilage is relatively immature. At this age, the cartilage structure is hypercellular and the matrix has a large fluid content, making the structures more resilient and less susceptible to ischemic injury.²⁰⁶

The pathogenesis of acquired subglottic stenosis is ischemic injury secondary to lateral wall pressure from the ETT. Ischemia results in edema, necrosis, and ulcerations of the mucosa. Secondary infection results in exposure of the cartilage. Within 48 hours, granulation tissue begins to form within these ulcerations. Ultimately, scar tissue forms, resulting in narrowing of the airway (Fig. 12-17).^207–209 Specimens obtained from partial cricotracheal resection in children were found to have severe and sclerotic scarring with squamous metaplasia of the epithelium, loss of glands and elastic mantle fibers (tunica elastica), and dilation of the remaining glands with formation of cysts.²¹⁰ Also, the cricoid cartilage was affected on the internal and external side, with irreversible loss of perichondrium on the inside and resorption by macrophages of cartilage on both sides.¹⁹⁴

FIGURE 12-17 The pathogenesis of intubation injuries. A, Schemata of a cross section through the glottis. Pressure necrosis causes ulcerations at the vocal processes of the arytenoids with exposed cartilage. Flaps of granulation tissue are present anterior to these ulcerations. B, Cross section of the glottis at this same level; straight arrows indicate flaps of granulation tissue, and curved arrows indicate the absence of mucosa and ulcerations with exposed cartilage on the vocal processes of the arytenoids. C, Intubation injury to a 2-month-old infant; straight arrows indicate granulation tissue, and curved arrows indicate area of ulcerations (white area). The most severe area of injury is usually at the level of the cricoid cartilage, resulting in subglottic stenosis.

(Reproduced with permission from Holinger LD, Lusk RP, Green CG. Pediatric laryngology and bronchoesophagology. Philadelphia: Lippincott-Raven; 1997.)

Factors that predispose to subglottic stenosis include use of an ETT that is too large, laryngeal trauma (e.g., traumatic intubation, chemical or thermal inhalation, external trauma, surgical trauma, gastric reflux),^211–213 prolonged intubation (particularly greater than 25 days), repeated intubation, sepsis and infection, chronic illness, and chronic inflammatory disease.^204,214,215

The Laryngeal Tube

The Laryngeal Tube (LT; VBM Medizintechnik GmbH, Sulz, Germany) is designed to secure a patent airway during either spontaneous breathing or controlled ventilation. This device is available with a single lumen for ventilation only or with a double-lumen tube that also allows suction of gastric contents. This system seals the esophagus at the distal end with a small cuff attached at the tip (distal cuff), and a larger balloon cuff at the middle part of the tube (proximal cuff) stabilizes the device and blocks the oropharynx and nasopharynx. The two openings that lie between the cuffs are positioned so that the more distal opening faces the glottis. The cuffs are inflated through a single pilot tube and balloon, through which cuff pressure can be monitored. There are three black lines on the tube, near a standard 15-mm connector, that indicate adequate depth of insertion when aligned with the teeth. The nondisposable device is made of silicone (latex free) and is reusable up to 50 times after sterilization in an autoclave. There are four variations: (1) standard single-lumen, reusable (LT); (2) single-lumen, disposable (LT-D); (3) double-lumen with drain tube, reusable (LT-suction II, or LTS II); and (4) double-lumen with drain tube, disposable (LTS-D) (E-Fig. 12-1).³⁰³ It is available in six sizes, suitable for neonates up to large adults (Table 12-5).

E-Figure 12-1 The Laryngeal Tube (LT) (VBM Medizintechnik GmbH, Sulz, Germany) is a single-lumen tube closed at the distal end with a small cuff attached at the tip (distal cuff) and a larger balloon cuff at the middle part of the tube (proximal cuff). The proximal cuff provides a seal in the upper pharynx, and the distal cuff seals the esophageal inlet. Two openings lie between the two cuffs, and the device is positioned so that the more distal opening faces the glottis. The cuffs are inflated through a single pilot tube and balloon, through which cuff pressure can be monitored. There are three black lines on the tube, near a standard 15-mm connector, that indicate adequate depth of insertion when aligned with the teeth. The LT is available in four types (standard LT, disposable LT, LT-suction II, and disposable LT-suction II) and in six sizes, including those that are designed for children. Specially marked and color-coded syringes are supplied to ensure proper cuff inflation. Two different sizes of the Laryngeal Tube are shown.

The LT should be inserted while the child’s head and neck are placed in the sniffing or neutral position. The tip of a well-lubricated LT is placed against the hard palate behind the upper incisors. The device is then slid down the center of the mouth until resistance is felt or the device is almost fully inserted. After connection to the anesthesia circuit, proper placement is confirmed by assessing ease of ventilation. Some adjustment (usually slight withdrawal) may be required to provide optimal ease of ventilation. Care should be taken not to push the tongue backward into the posterior pharynx. Ease of insertion of the standard LT is reported to be comparable to that of the LMA Classic, although the LT may require more readjustments of its position to obtain a clear airway.^304,305 The incidence of complications with the two devices appears to be similar.³⁰⁴ The LT may provide a better seal than the Classic LMA.³⁰⁶ Compared with the PLMA, the LT may be less effective and more difficult to insert.^307–309 Although the LT-suction device may have similar success to the PLMA,³¹⁰ there are scant data in children.^311–316 An initial report of its use in children ages 2 to 12 years found a successful placement rate of 96% (77/80 children). Complications occurred in two children; one had laryngospasm that resolved with deepening of the anesthetic, and the other complained of mild difficulty with swallowing postoperatively.³¹² A study comparing the LT with the LMA found it to be less effective for either spontaneous or assisted ventilation and for fiberoptic evaluation of the airway in children younger than 10 years of age.³¹¹ A study of 70 children using sizes 0 to 3 reported failure to place the LT in 12% of children. Failures were caused by inability to ventilate, hypoxemia, gastric insufflation, cough, and laryngospasm or stridor, particularly for children weighing less than 10 kg; therefore, the LT was not recommended for children of this size.³¹³ Although the manufacturer states that a flexible fiberoptic bronchoscope (FOB) may be passed through the device, the openings are of insufficient size to permit passage of an ETT.

The Cobra Perilaryngeal Airway

The Cobra Perilaryngeal Airway (CobraPLA; Engineered Medical Systems, Indianapolis, Ind.) is a disposable SGA that is marketed for the same indications as the LMA Classic but creates a seal more cephalad in the hypopharynx using a cylindrical inflatable cuff. The distal end of the device sits over the larynx, but the distal end is not inflatable (E-Fig. 12-2).^301,317,318 An initial report comparing the CobraPLA with the LMA Classic found that insertion time, airway adequacy, and number of repositioning attempts were similar. Peak airway sealing pressure was significantly greater with the CobraPLA; the authors concluded that the CobraPLA has better airway sealing capabilities than the LMA Classic.³¹⁹ A more recent group of investigators studying the CobraPLA in adults raised concerns about both the design and the safety of this device, particularly during controlled ventilation. After studying 29 patients, investigations were suspended and later stopped after two cases of significant pulmonary aspiration occurred in patients while using the CobraPLA.³²⁰ The device is available in eight sizes and can be used in infants as small as 2.5 kg (Table 12-6).³¹⁷ The distal grill has a long center slit that is specifically designed to allow passage of a fiberoptic bronchoscope (FOB) and ETT (the size 0.5 neonate CobraPLA allows easy passage of a 3.5 uncuffed ETT). In a pediatric study, the orientation of the larynx as viewed through the CobraPLA using video was obtained in 45 infants and children. An acceptable view of the airway was obtained in all subjects, but the laryngeal view was almost obstructed or completely obstructed by the folding of the epiglottis over the glottic opening in 77% of children weighing less than 10 kg. (A similar problem was encountered in approximately 80% of children managed with the LMA Classic as well.³²¹) The investigators suggested extra vigilance to prevent airway obstruction in small children. Also, because the grill bars of the CobraPLA were closely apposed to the epiglottis and supraglottic structures in almost all subjects, it was suggested that removal of the device in a deeper plane of anesthesia may minimize laryngeal stimulation. Further study of this device in children, particularly infants, is needed to define its role compared with the LMA.^322–324

E-Figure 12-2 The CobraPLA (perilaryngeal airway) (Engineered Medical Systems, Indianapolis) is a disposable supraglottic device that is marketed for the same indications as the laryngeal mask airway but creates a seal higher in the hypopharynx using a cylindrical inflatable cuff. Three different sizes are shown (A). The distal end of the device sits over the larynx but is not inflatable. A long midline slit in the distal end of the device allows passage of a fiberoptic scope and endotracheal tube (B).

The i-gel

The i-gel SGA (Intersurgical, Liverpool, N.Y.) consists of a dual-channeled, noninflatable laryngeal mask made from a gel-like thermoplastic elastomer (Fig. 12-20). It has a built-in bite block and is available in sizes 1, 1.5, 2, 3, 4, and 5 (Table 12-7). One channel functions as the airway tube while the second channel exits at the tip of the device and provides gastric access when seated properly. The lubricated posterior surface of the i-gel is inserted along the palate into the posterior pharynx. An observational study in 50 children reported easy insertion in all patients with a mean leak pressure of 25 cm H₂O; gastric access was successfully obtained in all children.³²⁵ A study that compared the i-gel to the Ambu AuraOnce laryngeal mask (Ambu, Glen Burnie, Md.) showed higher leak pressures and longer insertion times with the i-gel. The authors noted a tendency for the i-gel to slide out and recommended taping to prevent dislodgment intraoperatively.³²⁶

FIGURE 12-20 The i-gel supraglottic device (A) consists of a malleable non–latex-containing, noninflatable cuff that is designed to seal over the laryngeal inlet after insertion. The stem of the i-gel contains a “buccal cavity stabilizer” which is designed to resist accidental rotation after insertion and is made from a hard polymer that resists biting. The i-gel also contains a gastric suction channel next to the 15-mm connector (B), with which practitioners may evacuate gastric contents when the device is in the correct inserted position. C, The distal position of the suction port.

Summary

A variety of SGAs are currently available. Some are imitators of the LMA Classic but available at a reduced cost, whereas others are completely new designs. There are many new devices with various designs to assist in the management of normal and DAs in children, but there are insufficient data to clearly state that one device or one manufacturer is superior to another.

Documentation

Documentation of the DA and its management is essential to provide useful information for the next time that the child requires sedation or anesthesia. A note in the anesthesia record should clearly address the following issues:

FIGURE 12-22 The laryngoscopic grading system of Cormack and Lehane offers a reasonable means of describing visualization of the larynx. It is useful to grade the degree of visualization during laryngoscopy and how that visualization was achieved (e.g., external cricoid pressure or laryngeal manipulation, the size and configuration of the laryngoscope blade). This provides useful information for the next person attempting laryngoscopy so that he or she has some degree of knowledge regarding what to expect. Grade I is visualization of the complete laryngeal opening; grade II, visualization of just the posterior area; grade III, visualization of just the epiglottis; and grade IV, visualization of just the soft palate.

(Reproduced with permission from Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984;39:1105-11.)

In addition to discussion with the family and the child (when age appropriate), a letter should be given to the family and child outlining the difficulties with the airway, describing how the airway was managed, and referring them to the MedicAlert Foundation registry.³²⁰ This should be copied and circulated to the medical record and to the MedicAlert registry. In the United States, the MedicAlert registry for difficult airway/difficult intubation can be reached by telephone at 1-888-633-4298. Similar registries are also being formed internationally.³⁶⁰ The MedicAlert registration form asks for clinical details about the type of airway difficulty as well as which maneuvers were successful in management and which were not. Any practitioner who provides airway management to the registered patient can update this information at any time. Although scoring systems used in adults^83–87 have not been thoroughly investigated in all age groups,^88,361 it is useful to describe in detail the view of the larynx that was achieved and how it was achieved (e.g., blade type, size, external laryngeal manipulation).

The Unexpected Difficult Intubation

With careful preoperative evaluation and planning, the unexpected pediatric DA should be a rare occurrence. However, the practitioner should always be prepared for this potentially life-threatening event. Because the unexpected DA occurs after the anesthesia (plan A) has been initiated, many of the management decisions required for the anticipated DA have already been made. Of primary importance is maintaining adequate oxygenation while a definitive course of action is pursued (i.e., plan B, plan C, and so on). A reasonable decision tree, based on the DA algorithm of the American Society of Anesthesiologists (ASA), is presented in Figure 12-23. An important difference between infants and adults should be noted in this scenario. Because infants have an increased metabolic rate and decreased functional residual capacity, the time between the loss of the airway and resultant hypoxemia with potential secondary neurologic injury is significantly diminished compared with adults.³⁶² In a mathematical model, the approximate time to zero oxygen saturation from an Fio₂ of 90% is 4 minutes in a 10-kg child, whereas the same process in a healthy 70-kg adult takes almost 10 minutes.^360,363

FIGURE 12-23 A proposed algorithm for management of the unexpected difficult pediatric airway. LMA, Laryngeal mask airway; OELM, optimal external laryngeal manipulation; PLMA, ProSeal LMA. *Consider using PLMA if the child is at risk for aspiration or if high inflation pressures are needed.

(Modified with permission from Wheeler M. Management strategies for the difficult pediatric airway. Anesth Clin North Am 1998;16:743-761.)

Extubation of the Child with the Difficult Airway

Preparation for extubation begins shortly after the airway is secured. Equipment used to secure the airway should be rechecked, quickly returned to functional status, and then left in the operating room until successful safe extubation. Children who had prolonged attempts at intubation or who will have procedures that may lead to airway edema may benefit from IV dexamethasone (0.5 to 1 mg/kg, up to 20 mg). If significant airway edema is suspected, consider leaving the child intubated postoperatively until it resolves. The child must be fully awake and have full return of strength and adequate ventilatory effort before extubation is attempted.

A Cook airway exchange catheter with Rapi-Fit adapter (Cook Critical Care, Bloomington, Ind.) is a hollow plastic guide with holes on its distal end that may be useful as a bridge to extubation because the adapter on its proximal end allows the placement of either a Luer-Lok connector for connection to a jet ventilator or a 15-mm adapter for connection to a standard anesthesia ventilating system (E-Fig. 12-3).^364–367 It is available in a variety of sizes to allow the exchange of ETTs with 3.0 mm ID or larger. This can be used for oxygenation and ventilation and as a guide to reinsertion of the ETT if the child’s ventilatory efforts are inadequate or if airway obstruction occurs.³⁶⁸ However, caution is required when using this device for jet ventilation, because significant barotrauma has been reported.^369,370

E-Figure 12-3 Endotracheal tube exchangers are available that will fit an endotracheal tube (ETT) with a 3.0-mm ID. These have side holes at the tip that allow delivery of oxygen (A) and may be attached to either a jet ventilation system or a standard 22-mm OD adapter (B). This device is also available with a stylet and slight bend to be used as an intubation bougie (C). This device can be used to successfully reinsert the ETT should the patient fail extubation criteria. D, This child had a very severe facial burn and was intubated by the nasal route because he had such severe trismus that we were not able to open his mouth. Several days after grafting, he appeared to have satisfactory conditions for extubation. Given the degree of difficulty in placing the mask on his face, extubation was planned using an airway exchange catheter (RapiFit, Cook Critical Care). E, After preoxygenation and sedation with intravenous ketamine and midazolam in low doses, 1 mg/kg of lidocaine was sprayed down the ETT, and the airway exchange catheter was advanced into the trachea. E-Figure 12-3, cont’d F, The ETT was then removed, leaving the airway exchange catheter in place (G). H, The child was then administered oxygen by facemask and observed for satisfactory ventilation and oxygenation, after which the airway exchange catheter was removed.

An alternative to jet ventilation is the Enk Oxygen Flow Modulation set (Cook Critical Care), which allows flow from a standard low-pressure flow meter to be adjusted by occluding holes in the delivery system with the thumb and forefinger (E-Fig. 12-4, A). As a potential substitute for the Enk device, one could cut a side hole in the plastic oxygen delivery tubing to create a similar low-pressure oxygen delivery system (see E-Fig. 12-4, B). Pneumothorax, pneumomediastinum, and deaths have occurred when jet ventilation was used with an airway exchange catheter.³⁷¹ One report suggested that only insufflation or gentle manual ventilation should be used initially and that jet ventilation should be reserved for situations in which these techniques are ineffective. These authors also recommended that the optimal management was reintubation.³⁷²

E-Figure 12-4 A, A device that may be substituted for a jet ventilation system that allows delivery of oxygen at low flows is the Enk Oxygen Flow Modulation set (Cook Critical Care, Bloomington, Ind.). Occlusion of the side holes with the thumb and first finger allows diversion of flow into a transtracheal or translaryngeal cannula, and removal of the occlusion allows flow to exit the side of the device. B, A low-cost alternative is to simply cut a side hole in the oxygen delivery tubing and use it in the same way as the Enk system.

If the child will remain intubated for a prolonged period of time after surgery, it is advisable to return the child to the operating room for extubation. A surgeon who is prepared to perform rigid bronchoscopy and tracheostomy and an anesthesiologist who is familiar with the techniques used for the previously successful airway management should be in attendance.

Multi-handed Mask Ventilation Techniques

Multi-handed mask ventilation techniques can provide an effective temporizing measure until the airway is secured or the child is awakened. One person uses both hands to maintain an adequate mask fit, and a second person compresses the reservoir bag (Fig. 12-24). This can also be accomplished by having a single provider use two hands on the mask while the anesthesia ventilator is activated.³⁷³ Occasionally, a second person is required to perform a jaw thrust with one hand while compressing the anesthesia bag with the other. Rarely, a third person may be required to compress the anesthesia bag with two hands (in order to generate a greater peak inflation pressure) while the first person holds the mask with two hands and the second person performs a two-handed jaw thrust.³⁷³

FIGURE 12-24 A, The two-handed technique for mask ventilation may be useful to improve mask fit and therefore ventilation when the traditional technique is inadequate. One person holds the mask while a second person squeezes the ventilation bag. B, Occasionally, a third person is required to perform a two-handed jaw thrust (see text for details).

Laryngeal Mask Airway

The LMA has revolutionized DA management in children. Numerous case reports and extensive clinical experience attest to the value of the LMA for establishing an airway when both ventilation and intubation are extremely difficult or impossible.^{340,374–376} The LMA has been described as a tool for use in both the nonemergency pathway (cannot intubate, can ventilate) and the emergency pathway (cannot intubate, cannot ventilate [CICV]) of the ASA DA algorithm.^338,340 Use has been described in the awake child (LMA insertion in awake infants with Pierre Robin syndrome [Robin sequence])³⁷⁷ (Video 12-10) and in the anesthetized child with a known or suspected DA. It can be used as the definitive airway in some circumstances, as a conduit for intubation, or as a temporizing airway while other options are pursued (e.g., a surgical airway). There are now many other SGA devices reported to be useful in the management of the child with a DA, but comparative studies in pediatrics are lacking.^255,378

Percutaneous Needle Cricothyroidotomy

In 1992, the American Heart Association changed its recommendations for emergency airway management to a percutaneous needle cricothyroidotomy over a surgical cricothyroidotomy because it was believed that the former entails less risk of injury to vital structures such as the carotid arteries or jugular veins, particularly in the hands of nonsurgical trained practitioners. In addition, most practitioners can more rapidly perform the percutaneous procedure. However, the cricothyroid membrane has a relatively small width in infants and children. Attempts at cricothyroidotomy may readily damage cricoid and thyroid cartilages, resulting in laryngeal stenosis and permanent damage to the speech mechanism. Therefore, this procedure should be reserved for use only under emergency circumstances.^379,380

Because percutaneous needle cricothyroidotomy is rarely used, it is recommended that experience be gained with patient simulators or in animal models, because success in the hands of the inexperienced is not assured.^381,382 A schema of this procedure is presented in Figure 12-25. A commercial product called the Jet-Ventilation-Catheter (VBM) is available in three sizes: 16, 14, and 13 gauge. It consists of a slightly curved puncture needle within a Teflon, kink-resistant cannula nearly identical to an IV catheter (Fig. 12-26, A). This cannula has two lateral eyes at its distal end and a combined Luer-Lok and 15-mm adapter at its proximal end (see Fig. 12-26, B). It also has a fixation flange and foam neck tape to secure the airway.

FIGURE 12-25 Percutaneous cricothyroidotomy. Extend the head in the midline with a rolled towel or folded sheet beneath the shoulders. A, Standing to the left of the child, stabilize the trachea with the right hand. B, The cricothyroid membrane is located with the index fingertip of the left hand between the thyroid and cricoid cartilages. This space is so narrow (1 mm) in an infant that only a fingernail can discern it. The trachea is then stabilized between the middle finger and thumb of the left hand while the fingernail of the index finger marks the cricothyroid membrane. C, A large intravenous (IV) catheter (12 to 14 gauge) is then inserted through the cricothyroid membrane, and air is aspirated (D). The catheter is advanced into the trachea through the membrane, and the needle is discarded; an intraluminal position is reconfirmed by attaching a 3-mL syringe (E) and aspirating for air (F). A 3-mm adapter from a pediatric endotracheal tube can be attached to any intravenous catheter (G). Ventilation is accomplished by attaching to a breathing circuit with a standard 22-mm connector (H). An alternative would be to leave the barrel of the 3-mL syringe attached to the intravenous catheter, insert an 8-mm endotracheal tube adapter to the syringe barrel (I), and then attach to a ventilating system with a standard 22-mm adapter (J).

(From Coté CJ, Eavey RD, Todres ID, Jones DE. Cricothyroid membrane puncture: oxygenation and ventilation in a dog model using an intravenous catheter. Crit Care Med 1988;16:615-619, © by Williams & Wilkins.)

FIGURE 12-26 A, The Jet-Ventilation-Catheter (VBM Medizintechnik GmbH, Sulz, Germany) is available in three sizes: From left to right: 13 gauge (adult), 14 gauge (child), and 16 gauge (infant). It consists of a slightly curved puncture needle within a Teflon, kink-resistant cannula. The procedure for insertion is similar to that described in Figure 12-25. B, This cannula has two lateral eyes at its distal end and a combined Luer-Lok and 15-mm adapter (surrounding the Luer-Lok) at its proximal end, allowing either jet or standard ventilation. It also has a fixation flange and foam neck tape to secure the airway.

Percutaneous needle cricothyroidotomy provides only a means for oxygen insufflation and does not reliably provide adequate ventilation. In the spontaneously breathing patient, simple delivery of intratracheal oxygen (1 to 2 L/min) may be sufficient in the short term, because hypercarbia is generally well tolerated by healthy children.^379,383,384 A number of children with arterial CO₂ values well above 150 mm Hg have survived neurologically intact when adequate oxygenation was maintained.³⁸⁴ Therefore, simple oxygenation without attempts at ventilation may be all that is required to sustain life (Fig. 12-27). For the child without respiratory effort, there is a need to provide ventilation in addition to oxygenation. An Ambu bag with the pop-off disabled can provide limited ventilation through a percutaneous catheter, but these devices will be ineffective at standard pop-off pressures.^379,385 Extremely high ventilating pressures are required, but midtracheal pressures are significantly lower (10 to 16 cm H₂O).³⁷⁹ A percutaneous cricothyroidotomy catheter can also be used with a jet ventilation system. Jet ventilation via a catheter passed through a narrow glottic opening has been described.^386–389

FIGURE 12-27 A, Changes in arterial blood gases and pH are plotted over time for six dogs with spontaneous ventilation; baseline values in room air are plotted at time −3; values after 2 to 3 minutes of hypoxemia as a result of airway obstruction are plotted at time 0. Marked, sustained increases in arterial oxygen tension (Pao₂) follow cricothyroid membrane puncture with delivery of only 1.0 L/min oxygen. B, Changes in arterial blood gases and pH are plotted over time for five dogs that were not making spontaneous ventilatory efforts. Both oxygenation and ventilation were achieved with a self-inflating bag introduced through the cricothyroid membrane. Paco₂, Carbon dioxide tension; SEM, standard error of the mean; Sig., significant difference.

(From Coté CJ, Eavey RD, Todres ID, Jones DE. Cricothyroid membrane puncture: oxygenation and ventilation in a dog model using an intravenous catheter. Crit Care Med 1988;16:615-619, © by Williams & Wilkins.)

If upper airway obstruction is present (e.g., after multiple unsuccessful attempts at rigid laryngoscopy), there will be a limited pathway for the egress of air and oxygen, and barotrauma may result from insufflation of oxygen or attempts at ventilation. Very serious morbidity and mortality may result from massive subcutaneous emphysema or tension pneumothorax.^390,391 Therefore, jet ventilation must be used with extreme caution in infants and children.³⁹²

Another IV catheter–type emergency airway device is the Emergency Transtracheal Airway Catheter (Cook Critical Care), which consists of a 6-F reinforced catheter that is advanced over a 15-gauge needle similar to the devices described earlier (E-Fig. 12-5). One study simulated use of the Enk Oxygen Flow Modulation set with a variety of IV cannulae and the Emergency Transtracheal Airway Catheter. The investigators concluded that the device worked best when all holes on the Enk device were occluded simultaneously and that minimum flow should never be less than 1 L/min. They also suggested that initial fresh gas flow be set to 1 L/min and then adjusted up or down to effect.³⁹³ Successful ventilation with uncuffed devices may depend on the patency of the upper airway (i.e., the greater the patency, the less the effectiveness of ventilation in the nonbreathing patient).³⁹⁴ None of these devices has been examined in controlled trials to confirm efficacy, in part because these events are so rare. Therefore, we recommend training on simulators so that each practitioner can determine what device is best in his or her hands.

E-Figure 12-5 Top, A transtracheal kink-resistant catheter is available in a 6-F external diameter (Emergency Transtracheal Airway Catheter; Cook Critical Care, Bloomington, Ind.). The system is similar to a simple intravenous catheter device inserted percutaneously with a syringe (bottom). Aspiration of air confirms tracheal position, and the catheter is advanced as described in Figure 12-25. The catheter can be attached to either a jet ventilation system (top) or the system described in Figure 12-25.

A number of percutaneous emergency airway devices are available that use a short but large-diameter needle or a needle, guidewire, and dilator to aid insertion of a percutaneous airway.^{381,395–397} The Quicktrach (Rüsch) is a device that consists of a tapered 2- or 4-mm catheter with a fixation flange for securing with cloth tape. A removable plastic stopper is designed to limit the depth of needle insertion. This device requires several steps: puncture of the skin, aspiration for air, removal of the stopper, removal of the needle/syringe, and attachment to standard 22-mm connector. A flexible connector is also provided (E-Fig. 12-6). A rabbit model to simulate infant cricothyroidotomy found success in all attempts but 2 of 10 attempts resulted in fracture of the cricoid cartilage and 1 resulted in damage to the mucosa of the posterior tracheal wall.³⁹⁸ Conversely, this device has been shown to allow more rapid establishment of an airway than other devices that use a Seldinger technique.^399,400 A larger, cuffed adult model is now available (E-Fig. 12-7).

E-Figure 12-6 QuickTrach Emergency Cricothyroidotomy Device (Rüsch Inc., Duluth, Ga.) is available in three sizes (A and B, bottom to top): 1-mm neonatal, 2-mm toddler, and 4-mm older child. This device is similar to the devices presented in Figure 12-25, but the diameter of the introducing needle is larger and the final size catheter also has a larger diameter. A white plastic stopper (C) is designed to prevent excessive depth of insertion and is removed after successful entry into the trachea. The fixed curve of the large needle requires a change in angle from 90 degrees with the skin at insertion to 60 degrees with the skin after entry into the trachea. The built-in flange and strap allow rapid fixation. The size of these devices would seem to limit their utility to larger children and adults, and it would appear that some training on a simulator would be advised.

E-Figure 12-7 A and B, QuickTrach Emergency Cricothyrotomy Device for older patients. The device is shown assembled (A) and disassembled (B). The principles of insertion are similar to those described in Figure 12-25, but this device provides a much larger airway with a cuff, allowing better seal. It would appear that this device would only be appropriate for teenagers due to the size of the insertion needle.

Other devices that use the Seldinger technique (i.e., needle, guidewire, scalpel incision of the skin, and passage of a dilator and tracheostomy tube) are the Arndt and Melker devices (Cook Critical Care).⁴⁰¹ These devices provide a 3.0-mm ID airway that is sufficient for ventilation as well as oxygenation (E-Fig. 12-8). However, the time required to insert such devices may be longer than for simpler devices and may be inappropriate for immediate rapid establishment of an airway.^381,399,400 In contrast, a porcine cadaver study found greater comfort with this technique compared with a scalpel technique.⁴⁰² These devices are useful for elective percutaneous tracheostomy.⁴⁰³

E-Figure 12-8 The Arndt Emergency Cricothyrotomy Set (Cook Critical Care, Bloomington, Ind.) provides a 3.0-mm ID airway that is sufficient for ventilation as well as oxygenation. Percutaneous dilation cricothyroidotomy uses a five-step staged technique, similar to the Seldinger technique used for placement of central venous catheters, to place a secure airway. 1) A percutaneous needle cricothyroidotomy is performed, and negative pressure measured via a syringe and side port confirms aspiration of air. 2) A guidewire is then passed through the needle. The needle is removed, leaving the wire within the trachea. 3) A scalpel is used to puncture the skin. 4) A dilator and cricothyroidotomy tube together are threaded over the guidewire into the trachea. The dilator and guidewire are removed, leaving the cricothyroidotomy tube (airway) in place. A connection for jet ventilation is also provided. There is limited experience with this device in children, particularly infants. Other similar devices are available (see text for details).

Another device, Pertrach (Engineered Medical Systems, Indianapolis, Ind.), uses a split needle on a syringe to puncture the cricothyroid membrane (E-Fig. 12-9). A skin incision is made, and an introducer with tracheostomy tube (3.0-mm ID) is directed into the trachea, splitting the needle, which is removed. The introducer is then removed, and the airway is secured with tracheostomy tape. There are no case reports in the literature to determine the ease or difficulty of insertion in children, but the multiple steps required suggest that it may be a device for elective tracheostomy rather than emergent establishment of a surgical airway.

E-Figure 12-9 A, The Pertrach system (Pulmodyne, Indianapolis.) uses a split needle on a syringe to make a puncture through the cricothyroid membrane. B, An introducer/dilator is passed through the needle into the trachea. C, A skin incision is made and the introducer, together with a 3.0-mm ID airway, is advanced into the trachea while the needle is split and removed. The introducer is then removed, and the airway is secured with tracheostomy tape.

Another percutaneous tracheostomy device is the Bivona Pedia-Trake kit (Smiths Medical, St. Paul) (E-Fig. 12-10). A skin incision is made with a scalpel, and a large needle is introduced with a skin dilator, which in theory opens the incision sufficiently to allow passage of an obturator and a 3.0-, 4.0-, or 5.0-mm ID tracheostomy tube (with or without cuff). This device appears sufficiently complicated so as to not be useful in a CICV emergency; it might be better suited when there is an urgent need to establish surgical access to the airway.

E-Figure 12-10 A, The Bivona Pedia-Trake percutaneous tracheostomy device (Smiths Medical, St. Paul) uses a multiple-step technique that may not be appropriate for an emergent situation. A large-bore needle on a syringe is used to puncture the cricothyroid membrane, and surrounding the needle is a sharp, tapered dilation system. B, After successful entry into the trachea, the syringe and needle are withdrawn, and the opening is dilated. A size 3-, 4-, or 5-mm ID tracheostomy tube is then inserted and secured with tracheostomy tape.

Other devices with limited pediatric use³⁹⁵ are kits designed to place a full-sized tracheostomy tube, such as the Nu-Trake (International Medical Devices, Northridge, Calif.) and Abelson (Gilbert Surgical Instruments, Bellmawr, N.J.) devices. They may potentially cause tracheal or laryngeal injury in small patients because of the relatively large size of the needle; again, little experience in children has been published.^396,397,404

Laryngeal Mask Airway versus Percutaneous Needle Cricothyroidotomy and Transtracheal Jet Ventilation

The LMA Classic has proved to be an extremely useful device in airway emergencies. In contrast to percutaneous needle cricothyroidotomy, it is an effective device for ventilation as well as a conduit for intubation. The LMA is easily inserted and requires a relatively low level of skill, as demonstrated in numerous studies comparing this technique with other airway management skills (e.g., mask ventilation, endotracheal intubation). More importantly, in contrast to transtracheal jet ventilation, the complication rate with the LMA Classic is exceedingly low.⁴⁰⁵ However, this is an SGA device. If glottic or subglottic obstruction to ventilation is present, it will be ineffective, and a surgical airway with or without transtracheal jet ventilation is still the emergency technique of choice. Since the introduction of the LMA, clinical experience suggests that if glottic or subglottic pathology is not suspected, LMA placement to establish ventilation may be appropriately attempted first.³⁴⁰

Surgical Airway

Establishing a surgical airway emergently requires great technical skill. It is difficult to perform quickly, and other methods to provide oxygenation should be pursued first. In nonemergent airway management for children, a tracheostomy is preferred to a cricothyroidotomy because of fewer long-term complications and better results with later decannulation of the airway.^381,406

Anterior Commissure Scope and Rigid Ventilating Bronchoscope

Two pieces of equipment used by otolaryngologists that can assist in visualizing the larynx and providing a method of ventilation are the anterior commissure scope and the rigid ventilating bronchoscope. The anterior commissure scope is a rigid, tubular, straight-blade laryngoscope with a light at the tip. The technique to place the anterior commissure scope and the advantages for visualization are similar to those described later for the straight blade used with the retromolar approach.⁴⁰⁷

Rigid Laryngoscopy

The rigid laryngoscope is the most familiar and most universally available piece of airway equipment; therefore, it is critical for the practitioner to become facile in its use and to know a variety of techniques. Some suggestions are reviewed here. It is reasonable to take a second look with the rigid laryngoscope after an unexpected failed intubation; however, a good rule is to always change something about the approach that may improve visualization. In the past, awake rigid intubation was the traditional approach to the problematic neonatal airway, but this approach should be used only in an extreme emergency or when IV access is not available.^133–136 Some anatomic features are completely unfavorable for success with the rigid laryngoscope, regardless of technique. Repeated unsuccessful attempts should be avoided, because this can lead to airway trauma and edema. Because infants and children already have smaller airway structures, they are uniquely susceptible to a rapid progression from “cannot intubate, can ventilate” to the CICV scenario.

Whether the child has a normal or an abnormal airway, it is essential to ensure correct positioning and to use age-appropriate equipment. The following maneuvers have been found to be helpful in achieving successful intubation of the child with a DA.

Intubation Guides

Intubation guides include plastic-coated, flexible metal stylets and the gum elastic bougie. These can be used for blind placement of the ETT under the epiglottis. A flexible stylet is placed inside the ETT and preformed to shape the ETT tip to one that will optimize intubation success (see Fig. 12-21). A hockey-stick configuration is frequently useful, particularly if only the epiglottis or the most posterior portion of the glottis can be visualized. The gum elastic bougie has a preformed, angled tip. It is placed alone and then the ETT is threaded over it and into the trachea (E-Fig. 12-11). When the bougie is successfully placed in the trachea, one can detect the subtle “bumpy” feel of the bougie making contact with the anterior tracheal rings. This device may also be used to facilitate intubation through an LMA or as an adjunct to other airway devices.^412–415

E-Figure 12-11 A gum elastic bougie may be used as a guide to pass the endotracheal tube into the laryngeal inlet. A hockey-stick configuration is frequently useful, particularly when only the epiglottis or the most posterior portion of the glottis can be visualized. The gum elastic bougie has a preformed angled tip. When the bougie is successfully placed in the trachea, one can detect the subtle “bumpy” feel of the bougie making contact with the anterior tracheal rings. This device may also be used to facilitate intubation through a laryngeal mask airway or as an adjunct to other airway devices.

Oxyscope

The Oxyscope (Heine Optotechnik, Herrsching, Germany) is a Miller 1 laryngoscope blade with an insufflation channel along its length so that it may be attached to an oxygen source. An Oxyscope provides increased Fio₂ and is particularly useful for intubation in spontaneously breathing neonates with high oxygen consumption in whom desaturation may rapidly develop (E-Fig. 12-12).^416–418

E-Figure 12-12 A, The Oxyscope (Heine Optotechnik, Herrsching, Germany), a modified laryngoscope, delivers 2 L/min of oxygen and, if connected to the anesthesia circuit, anesthetic agent at the tip of the blade during laryngoscopy. B, Increased levels of arterial oxygen tension (Po₂) were achieved during laryngoscopy of spontaneously breathing infants.

(From Todres ID, Crone RK. Experience with a modified laryngoscope in sick infants. Crit Care Med 1981;9:544-5, © Williams & Wilkins.)

Retromolar, Paraglossal, or Lateral Approach using a Straight Blade

Use of a straight blade in a retromolar approach may allow glottic visualization when the classic rigid intubation technique fails, particularly if the difficulty is secondary to a large tongue or small mandible (Fig. 12-28)^{407,410,413,420–424} With the child’s head turned slightly to the left, a no. 1 Miller blade is introduced into the extreme right side of the mouth. It is advanced in the space between the tongue and the lateral pharyngeal wall; the tongue is swept completely to the left and is essentially bypassed. It is very helpful to have an assistant pull back the right corner of the mouth with a small retractor (e.g., Senn retractor) to increase the space for ETT placement. The blade is advanced while staying to the right, overlying the bicuspids and lateral incisors until the epiglottis or the glottis is visualized. When the epiglottis comes in view, it is lifted with the blade tip to expose the glottic opening. It is extremely unlikely that pressure from the laryngoscope blade on the bicuspids and lateral incisors could loosen these teeth, because they have double roots or longer roots than the central incisors.

FIGURE 12-28 A through C, The retromolar, paraglossal, or lateral approach to rigid laryngoscopy utilizing a straight blade. Notice that the child’s head is turned to the left and that the laryngoscope blade is inserted over the molars toward the glottic opening (see text for details).

At this point in the laryngoscopy, it may be possible to move the proximal end of the blade toward the midline of the mouth to increase room for ETT placement and manipulation, although care must be taken to avoid applying pressure on the central incisors of the maxilla, lest they become loosened. If the glottis is not visualized, the head can be rotated farther to the left and the blade can be kept lateral to improve visualization. The ETT should be styleted and formed into a 90-degree bend configuration to assist in placement (see Fig. 12-21), particularly if the view of the glottis is only partial. A shorter-length blade (usually a Miller no. 1, even in older children) than that used in the traditional midline approach is chosen because the distance to the glottis with this method is greatly shortened.

Several mechanisms are responsible for the improved view of the glottis with the retromolar approach to laryngoscopy. First, there is a reduced need for soft tissue displacement and compression because the lateral placement of the blade bypasses the tongue. This approach to an improved view of the glottic opening is particularly useful for children with micrognathia.^{410,413,421,423,424} In such children, the space available to displace the tongue is reduced compared with the traditional midline approach to rigid laryngoscopy. Second, there is an improved line of visualization because the incisors and maxillary structures are bypassed by lateral blade placement and by shifting of the head to the left. Third, the use of a straight blade avoids the possible intrusion of a curved blade into the line of site.^{407,420–422} Finally, both the angle and the distance from the insertion of the straight blade at the right commissure of the mouth are reduced, facilitating an easier view of the glottic opening, particularly during a difficult intubation, compared with inserting the blade in the midline.

Fiberoptic Laryngoscopy

An advantage of using the FOB for intubation of the child with a DA is that it does not require extensive head or neck manipulation and is therefore useful in children who have cervical inflexibility (Klippel-Feil syndrome) or cervical instability (Down syndrome, achondroplastic dwarfism, trauma) (Video 12-9 and 12-11). The technique is also versatile because the flexible instrument conforms to a variety of abnormal airways; it is well tolerated by the sedated, spontaneously breathing child.³⁴⁴

Its disadvantage is that the fiberoptic bundle is small, permitting only a limited field of vision. For this reason, the presence of blood or copious secretions may render the FOB ineffective. In addition, use of the FOB requires extensive experience and practice in normal airways first. Our experience suggests that each size of available FOB should be used in at least 20 normal airways before use is attempted in an abnormal airway.⁴²⁵ Practice with all available sizes of FOBs is important because the manual skills required for each size differ somewhat. Also, FOBs are fragile and expensive. Great care must be taken when using and storing FOBs to prevent breakage of the fiberoptic bundles and the adjustable tip mechanism. They must also be sterilized between uses to maintain the patency of the working channel and clear, bright vision through the fiberoptic bundles and to avoid transmission of infection.

Ancillary Equipment

Endoscopy masks can be used to provide oxygen to the spontaneously breathing child and to ventilate the paralyzed child during fiberoptic laryngoscopy. The Frei endoscopy mask (E-Fig. 12-13) and the Patil-Syracuse endoscopy mask are commercially available.^426,427 Patil-Syracuse masks are available in a child size but are too large for most children younger than age 4 years.⁸⁸ The Frei mask configuration allows the FOB to be placed in a central position, overlying the nose and mouth, which is more favorable for tracheal intubation. The clear membrane with the hole for the bronchoscope can be rotated to allow either oral or nasal approaches. Alternatively, a disposable facemask can be combined with a bronchoscopic swivel adapter.⁴²⁸ The FOB can then be passed through the diaphragm of the adapter while ventilation is maintained via the anesthesia circuit. There are two types of commercially available adapters. One type attaches directly to an anesthesia mask. The other type is designed to attach to the ETT and can be modified to fit on the anesthesia mask by the use of a 15- to 22-mm adapter.

E-Figure 12-13 The Frei endoscopy mask is used for oxygenation and ventilation of a patient. A fiberoptic laryngoscope with a softened endotracheal tube of appropriate size presoaked in warm sterile water (not shown) is passed through a membrane opening in the mask. This allows one to maintain a constant depth of anesthesia and continuous oxygenation while visualizing the airway with the fiberscope.

Commercial oral airways designed for use in bronchoscopy are available for pediatric patients (IMD Inc., Park City, Utah); however, there are only three sizes (infant, child, and adult), and no studies have evaluated their usefulness in assisting fiberoptic intubation in children. Guedel airways can also be modified for use as oral intubation guides.⁴²⁸ A strip is cut from the convex surface of the airway to create a channel for placement of the FOB. This modified airway may be used to maintain a midline approach to the glottis; however, it is ineffective as a bite block.

Direct Technique

The optimal position of the child for fiberoptic bronchoscopy is different from the position for rigid laryngoscopy. The head should be flat on the table and slightly extended at the atlantooccipital joint to prevent the epiglottis from obstructing a view of the glottic opening.⁴²⁹ If an oral approach is selected, it is vital that the FOB pass in the midline. A nasal approach may make midline placement simpler and avoids the risk of the child’s biting the FOB or ETT. One useful technique is to apply oxymetazoline to the naris, place a lubricated nasal trumpet into the nares, and then insert a 15-mm connector from a tracheal tube into the nasal trumpet. This allows oxygen and inhalation agent to be delivered to the child while performing standard fiberoptic laryngoscopy (see Videos 12-9 and 12-11). However, the oral approach offers several advantages over the nasal approach, including avoidance of shearing adenoidal tissue and nasal bleeding. The oral approach may also be less stimulating and better tolerated than the nasal approach. If nasal intubation is chosen in a young child, a topical vasoconstrictor will reduce the risk of bleeding. With both approaches, an assistant should perform a jaw thrust to open the posterior pharyngeal and supraglottic spaces. Alternatively, a bite block or intubating airway may be used. Occasionally, the best view is obtained by direct traction on the tongue, which optimally opens the posterior pharynx. This can be accomplished by grasping the tongue with a gauze, plastic forceps, a stitch through the tongue, or application of high suction to the underside or tip of the tongue (Fig. 12-29).⁴³⁰

FIGURE 12-29 Suction can be applied to the tip of the tongue to facilitate pulling it forward to improve glottic visualization. This technique is particularly useful when the tongue is slippery due to secretions or if the mouth opening is small and prevents direct grasping of the tongue with a dry gauze.

The tip of the FOB should be introduced behind the tongue and gradually advanced in the midline under direct vision until a recognizable structure is observed. It is essential that the FOB be kept rigid so that when the direction of the tip is altered it remains in the same plane as the handle of the FOB. When the FOB is rotated, the tip should be slightly bent to provide a panoramic view. In general, the tip of the FOB is passed into the trachea before any attempts are made at passing the ETT through the nose or oropharynx. Because the distances in the oropharynx in children are less than in adults, the most common initial error when using this technique is to advance the FOB too deeply and into the esophagus. To avoid this pitfall, the FOB should be advanced only toward identifiable airway structures.

Once the FOB is introduced into the airway, a common problem is resistance to passage of the ETT. To minimize this occurrence, the ETT should be loaded onto the scope with the bevel facing down (Murphy eye up) for oral intubation and bevel facing up for nasal intubation.^431,432 This can be remembered by the mnemonic UNDO: bevel Up for Nasal intubation, Down for Oral intubation (see Video 12-10).⁴³³ If persistent resistance is encountered while attempting to pass the ETT past the glottic opening, the ETT should be rotated 90 to 180 degrees to place the bevel in a more favorable orientation for passage through the vocal cords. The depth of anesthesia or sedation as well as oxygen saturation (pulse oximetry) must be carefully monitored throughout the procedure. Arrhythmias may be avoided by providing an adequate depth of analgesia/anesthesia and ensuring a patent airway.

Fiberoptic laryngoscopy techniques should be perfected on manikins and on children with normal anatomy before such techniques are attempted on children with pathologic airway anatomy.^434–440 In a study that compared the time to intubation and complications in 40 infants with the Miller no. 1 laryngoscope or the Olympus LFP FOB, the time to intubation was slightly greater with the FOB (22.8 versus 13.6 seconds), whereas the complication rate was similar.⁴⁴¹ The authors concluded that routine use of the FOB for intubation in normal infants is a safe and reasonable method to gain and maintain skills with this technique.⁴⁴¹ For children, video-assisted fiberoptic intubation appears to offer advantages over fiberoptic intubation using a traditional eyepiece. These include faster mastering of this skill and an overall improved success rate when compared with the traditional method.^425,442

Lighted Stylet

A lighted stylet (light wand) is a useful adjunct for managing the pediatric DA (E-Fig. 12-14).^452–456 A number of these devices are available: Trachlight (Laerdol Medical Corporation, Wappingers Falls, N.Y.), Surch-Lite Lighted Intubation Stylet (Aaron Medical Industries, St. Petersburg, Fla.), Light Wand (Vital Signs, Totowa, N.J.), and Trachlite (Rüsch, Tuttlingen, Germany). These devices essentially comprise a malleable stylet with a high-intensity light at the tip; the stylet is shaped into a curve similar to that anticipated for successful passage into the laryngeal inlet (45 to 90 degrees). To begin, an ETT is passed over a well-lubricated lighted stylet. The tip of the stylet should remain within the tip of the ETT to minimize the potential for airway trauma. The room lights should be dimmed at this time to ensure that the stylet is visible when the wand is in the mouth. The lighted stylet is then introduced into the mouth while the proximal end of the stylet is flat against the cheek. As the stylet is inserted into the mouth, the proximal end of the handle is rotated counterclockwise until it is upright. The stylet continues to pass through the oropharynx, following the curvature of the tongue. If the tip of the lighted stylet is not in the proper position (e.g., in the esophagus), a diffuse light or no light will be observed on the surface of the neck. Proper position is usually ensured when a sharp, well-defined, bright circle or cone of light is observed transilluminating the neck directly in the midline at the level of the cricothyroid membrane (see E-Fig. 12-14). Once proper position is ensured, the ETT is gently advanced and the stylet is removed.^455,457

E-Figure 12-14 Lighted stylets are available from a number of manufacturers. A, Trachlight (Laerdol Medical Corporation, Wappingers Falls, N.Y.). B, Surch-Lite Lighted Intubation Stylet (Aaron Medical Industries, St. Petersburg, Fla.). Also available are the Light Wand (Vital Signs, Totowa, N.J.) and the Trachlite (Rüsch, Tuttlingen, Germany). These devices provide a blind method for placing larger-sized endotracheal tubes. C, A bright light on the surface of the neck at the level of the larynx indicates the correct location for passage into the trachea. If no light is visible, this usually indicates passage into the esophagus.

This technique is useful in those children in whom there is no intrinsic laryngeal or airway pathology but in whom visualization is anticipated to be difficult. The light wand may also be of value in children with a fracture of the cervical spine, because tracheal intubation can be accomplished with minimal movement of the neck.⁴⁵⁸ The hemodynamic response to intubation with this technique is similar to that observed with rigid laryngoscopy.⁴⁵⁴ The limitations of this technique are that it is a blind technique, the diameter of the device limits it use to larger-sized ETTs, and it may require multiple attempts; however, the success rate markedly increases with experience.^455,457 The most common cause of difficulty in passing the ETT is that the tube hangs up on the epiglottis. When this occurs, the lighted stylet may be withdrawn and its position slightly adjusted more posterior to allow passage behind and beyond the epiglottis. Alternatively, the ETT can be rotated along the long axis of the stylet so that the bevel is facing up. Our advice for using this technique is similar to that for bronchoscopy: it should be used in children with normal anatomy to gain the necessary experience required for managing children with abnormal airway anatomy. This adjunct has also been combined with an LMA to guide the stylet into the trachea.⁴⁵⁹

Bullard Laryngoscope

The Bullard laryngoscope is used for direct visualization of the laryngeal inlet in children with airway pathology (E-Fig. 12-15). It is available in three sizes: adult, pediatric, and pediatric long. This instrument combines fiberoptic bundles and mirrors. It is positioned within the larynx like a laryngoscope blade, and the direction of force used to displace the tongue is similar to that used with a standard laryngoscope, although this is not intuitively obvious from its configuration. It is designed to provide visualization around a 90-degree bend at the tip (i.e., around the base of the tongue). This configuration may be helpful for direct visualization of the larynx in children with mandibular hypoplasia syndromes (e.g., Robin sequence, Treacher Collins syndrome,⁴⁶⁰ Goldenhar syndrome, cervical fracture restricting motion), when the acute angulation of the base of the tongue to the glottic opening is exaggerated, and in children with congenital trismus (Hecht syndrome).⁴⁶¹ The technique used in children is different from that used in adults. Once the laryngeal inlet is visualized, a styleted ETT, with a bent configuration similar to the curve of the Bullard laryngoscope (see Fig. 12-21, B), is inserted just to the side of the Bullard laryngoscope blade and advanced under direct vision into the trachea. Success with this instrument is directly proportional to the experience of the anesthesiologist, because the perspective seen through this laryngoscope, the method of visualization, and the indirect method of ETT placement are so different from standard laryngoscopy.^462,463

E-Figure 12-15 The Bullard laryngoscope is available in three sizes: adult, pediatric, and pediatric long. The device shown at the top is the adult version, which has an attached endotracheal tube guide; the pediatric versions do not have this guide. This instrument combines fiberoptic techniques and mirrors; the fiberoptic bundles are contained within an instrument that functions and is positioned within the larynx like a laryngoscope blade. It is designed to provide visualization around a 90-degree bend at the tip (arrow) (i.e., around the base of the tongue). This configuration may be helpful for direct visualization of the larynx in children with mandibular hypoplasia syndromes (e.g., Pierre Robin syndrome, Treacher Collins syndrome, Goldenhar syndrome, cervical fracture restricting motion) when the acute angulation of the base of the tongue to the glottic opening is exaggerated. Once the laryngeal inlet is visualized, a styleted endotracheal tube with a bent configuration similar to the curve of the Bullard laryngoscope (see Fig. 12-21, B and C) is inserted just to the side of the Bullard laryngoscope blade and advanced under direct vision into the trachea.

Despite the availability of pediatric Bullard layngoscopes,⁴⁶⁴ adult scopes have also been successfully used in children.^465,466 Although tracheal intubation in children 1 to 5 years of age with a Bullard laryngoscope takes more time than with a Wis-Hipple 1.5 blade, the adult Bullard laryngoscope complements the Wis-Hipple 1.5 blade. Occasionally, the Bullard laryngoscope provides a superior laryngeal view and thus allows successful intubation when a failure with the Wis-Hipple blade occurs. When multiple passes of the tube off the adult Bullard laryngoscope were required, this is usually because of contact with the right aryepiglottic fold or anterior vocal cord. The latter appears to be more problematic when the adult laryngoscope is used in children.^465,466

Additional limitations of the Bullard laryngoscope are that the ETT can partially obstruct the view of the larynx during insertion and that it can be used only for oral intubation.⁴⁶⁴ An advantage is that there appears to be minimal motion of the cervical spine in patients with cervical spine disarticulations.^467–469

Retrograde Wire-Guided Intubation

The technique of retrograde wire-guided intubation utilizes transtracheal passage of an IV catheter through the cricothyroid membrane into the larynx and retrograde passage of a guidewire from a Seldinger vascular cannulation set to create a guide for intubation.^470–477 A commercial kit is available for use with ETTs that are 5 mm ID or larger (Cook Critical Care). This technique is rarely used in children because of the greater compressibility of the trachea and the increased risk of posterior tracheal wall perforation by the catheter in children compared with adults.

Video and Indirect Intubating Devices

Advances in technology have led to the reduction in size of video cameras and optical lenses. The integration of these devices into various laryngoscopes and stylets has produced several enhanced tools for securing the airway in children.⁴⁷⁸ Several of these new scopes improve visualization during laryngoscopy^{412,479–485} and perform better than traditional laryngoscopy in children with difficult direct laryngoscopy.^486–492 However, they are often associated with prolonged time to intubation compared with direct laryngoscopy, and their utility is limited in the presence of blood and secretions. These new devices can be categorized as (1) video laryngoscopes, which incorporate a video camera into the tip of the device; (2) optical laryngoscopes, which use a series of mirrors, prisms, or both to transmit the image from the tip of the device; and (3) optical stylets, which incorporate video or optical systems into a rigid or malleable stylet.