There are significant physiologic, anatomic, and equipment differences between children and adults that must be considered when planning the approach to the emergent pediatric airway. The presentation of a critically ill child requiring intubation is relatively uncommon compared to adults. ^1,2,3 This chapter presents the physiologic and anatomic characteristics of the pediatric airway, strategies for effective airway management, and organization methods for equipment to minimize errors in equipment sizing and medication dose calculation. ⁴

Due to a higher metabolic rate, oxygen consumption is increased in children, especially in infants. Infants and children have an increased relative cardiac output and minute ventilation to match the increased metabolic demand. However, children are vulnerable to rapid desaturation when oxygenation or ventilation is reduced. Children have relatively small-volume lungs with small functional residual capacities. This translates into a reduced oxygen reservoir, which decreases the effectiveness of preoxygenation and makes optimal preoxygenation more difficult. Therefore, be prepared to support oxygenation with bag-mask ventilation, often before an intubation attempt, while awaiting the onset of induction and paralysis. Attempts at intubation may need to stop once oxygen saturation drops below 90% to allow for bag-mask ventilation before the next attempt. Below an oxygen saturation of 90%, desaturation is particularly rapid. ⁵ The vast majority of children are easily bag ventilated when the proper technique is used, even when partial obstruction is present. The key is anticipation and early use of good bag-mask ventilation.

Children can develop gastric distention from air swallowing during distress as well as insufflation during bag-mask ventilation. Gastric distention can further compromise functional residual capacity, tidal volume, and ventilation. Early placement of an orogastric or nasogastric tube may remedy this. Gastric tubes have also been recommended to minimize the risk of reflux from an incompetent gastroesophageal junction, but the incidence of aspiration in children appears to be quite low, even in emergent intubation.

Children have a proportionally larger extracellular fluid compartment than adults. This results in a quicker onset and shorter duration of action of drugs and may require higher doses per kilogram for many of the drugs used to facilitate rapid-sequence intubation.

There are a number of anatomic characteristics of children that must be appreciated to optimize the success of endotracheal intubation (Table 111–1). Most of the unique anatomic characteristics are present in the first few years of life. From 2 to 8 years of age, there is a transition to a smaller but similarly proportioned anatomy compared to adults. Most children do not have the many acquired anatomic challenges present in older adults, and the differences in children are predictable. With good technique and anticipation of these differences, the majority of pediatric airways are successfully managed.

Alignment of the oral, pharyngeal, and tracheal axes, to allow visualization of the glottis, is affected by several features most pronounced in the infant: (1) a relatively large head and occiput, (2) a disproportionately large tongue and small mandible, and (3) a larynx that is more superior and anterior than in adults. This acute angle can be overcome by extending the neck (unless cervical injury is suspected) and, in some cases, placing a small roll under the shoulders (Figure 111–1).

The use of a straight laryngoscope blade is helpful in the presence of a large tongue and redundant soft tissues. The infant glottic opening, epiglottis, and aryepiglottic folds are more prominent, soft, and mobile than in an adult or older child. This redundant tissue can obscure the view and make it hard to identify the trachea. Under tension from a laryngoscope blade, the esophageal inlet can appear similar to the cords, because it can form a triangle and the edges appear white when stretched.

The narrow trachea, combined with the redundant, mobile periglottic tissues, predisposes the young child to airway obstruction. ⁶ The narrowest point of the child’s trachea is at the cricoid ring, which is also the site of mucosal swelling associated with croup. Airway resistance increases disproportionately with any reduction in diameter and dramatically increases when airflow becomes turbulent rather than laminar. A 25% reduction in diameter from swelling (e.g., 4 mm to 3 mm) reduces the cross-sectional area by 50% and increases resistance by 200%. The swollen, mobile tissues create a dynamic obstruction, and, in the agitated, crying, young child with subsequent turbulent airflow, the work of breathing can increase 32-fold. ⁷ This can lead to complete obstruction and respiratory arrest. This principle underscores the need to keep children with partial airway obstructions as calm as possible in a quiet, comforting environment. Because the obstruction is dynamic, children with airway edema usually respond well to positive-pressure bag-mask ventilation. Also, croup—by far the most common infectious cause of pediatric upper airway obstruction—causes inflammation below the glottic opening, and laryngoscopy usually provides normal visualization of the cords.

Some procedures are not indicated in children because of anatomic differences. Blind nasotracheal intubation is relatively contraindicated in children <10 years old, because the prominent adenoidal and tonsillar lymphoid tissue is likely to bleed and the acute airway angles described earlier make success less likely. Also, surgical cricothyrotomy is contraindicated in children <10 years old because the cricothyroid membrane is too small. Therefore, in children <10 years of age, needle cricothyrotomy is the subglottic, invasive airway of choice. ⁸

The principal challenge with children is selecting the appropriate-size equipment. Although there are formulas that can assist in the estimation of equipment sizing, all EDs should have pediatric airway equipment stocked and organized by age or size and easily accessible. Equipment restocking must also be reliable, so that all sizes are immediately available when needed. The Broselow^® tape represents a system that uses length-based estimates of equipment and medications, organized by color. ⁷ Airway carts can be similarly color-coded. Regardless of the system used, the goal is to eliminate reliance on memory to determine the best equipment size and medication dose.

ENDOTRACHEAL TUBES

Endotracheal tube size can be estimated by using the Broselow^® length-based system noted earlier. The following formulas can also reasonably estimate the size, as measured by internal diameter in children >1 year of age: 

Endotracheal tubes with <5.5-mm internal diameter are traditionally recommended to be uncuffed. This is because the cricoid ring represents the narrowest point of a pediatric airway and serves as a physiologic cuff. More recent data suggest that the use of cuffed tubes in younger children is safe; however, cuff inflation pressures must be closely monitored ( Tables 111–2 and 111–3 ). Cuffed tubes may be beneficial in cases where high airway pressures or changing compliance are anticipated (e.g., asthma, pneumonia, acute respiratory distress syndrome).

LARYNGOSCOPE BLADES

Straight laryngoscope blades (Miller) are preferred to curved blades in young children because the large epiglottis can be lifted directly and the large tongue is more easily displaced to provide direct visualization. A blade that is too small or short is potentially more difficult to use than one that is too large, because a short blade may not reach the supraglottic area. To determine proper blade length, place the blade handle joint at the child’s upper incisors and the tip at the angle of the mandible. The length of the blade from its tip to the handle joint should be within 1 cm proximal or distal of the angle of the mandible. ⁹ The #0 straight (Miller) blade or #1 curved (MacIntosh) blades are only used for the small or premature newborn ( Figure 111–2 ).

AIRWAY ADJUNCTS

Oversized masks do not allow a proper seal. Proper mask size is shown in Figure 111–3 . Correct sizing is also needed for stylets, bag-mask ventilators, oxygen masks, and suction. Undersized bag-mask ventilators (250 mL) do not provide adequate tidal volume for most children.

The selection of alternative airway techniques or rescue devices for children is limited. However, most children can be bag-mask ventilated should laryngoscopy fail. Intubating stylets, or bougies, are available in pediatric sizes small enough to accept a 3.0-mm internal diameter endotracheal tube. The Combitube is not recommended for patients <48 inches tall.

As noted in the earlier section “Anatomic Characteristics,” emergency subglottic, surgical airways in children <10 years of age are restricted to needle cricothyrotomy. The indications for these alternative airway options are discussed in more detail below.

NONINVASIVE VENTILATION

Noninvasive ventilation has been used in adult patients as a technique for respiratory support in order to stave off intubation. Its application has been most rigorously studied in adult congestive heart failure and chronic obstructive pulmonary disease. Studies in children have focused mostly on respiratory support in bronchiolitis. Nasal continuous positive airway pressure and high-flow (i.e., 6 L/min) nasal cannula, where humidified oxygen is delivered via nasal cannula, have been evaluated in the literature as means to support respiratory effort in infants and children with bronchiolitis. ^10,11,12,13 Use of this technique has been shown to improve ventilation and, in some children, obviate the need for subsequent intubation and should be considered as an adjunct in cases of moderate to severe bronchiolitis. Another form of noninvasive ventilation, bilevel positive airway pressure, may be useful in chronic conditions associated with respiratory insufficiency such as neuromuscular disorders or syndromes associated with anatomic upper airway obstruction (e.g., craniofacial syndromes, Down’s syndrome with macroglossia), as well as acute conditions including asthma. ^14,15

PREPARATION FOR INTUBATION

Begin preparation for endotracheal intubation when noninvasive means of ventilatory support and oxygenation are insufficient. Initiate preoxygenation, even if oxygen saturation is 100%. Maximize preoxygenation through elevation of the head of the bed when possible and high-flow oxygen through a non-rebreathing mask. Prepare appropriately sized equipment before initiating rapid-sequence intubation. Prepare different sized blades and at least one size smaller endotracheal tube. Make sure that oral and endotracheal suction catheters are functioning and of proper size. Assess airway difficulty (see later section “The Difficult Pediatric Airway“) and have rescue devices at hand. In some situations, such as partial airway obstruction, the best strategy may include anesthesia or otolaryngology consultation and consideration of intubation in the operating room. Even if the plan is to defer final management to another setting or a consultant, have equipment at the bedside in case of clinical deterioration requiring immediate action. Specialty equipment, such as a pediatric Magill forceps for foreign body obstruction, should also be at the bedside.

Ensure reliable IV access. In cases of urgency and no IV access, an IO line may be needed. Finally, a fluid bolus (20 mL/kg normal saline) is often beneficial before initiation of rapid-sequence intubation. Many children require intubation for respiratory failure, which is often associated with dehydration from reduced oral intake and increased insensible losses. In addition, positive pressure resulting from ventilation after intubation may decrease preload, making preintubation fluid resuscitation important.

BAG-MASK VENTILATION

Bag-mask ventilation is frequently required in children, and good technique is important. Rapid oxygen desaturation in children requires bag-mask ventilation before any laryngoscopic attempt, and bag-mask ventilation is the principal rescue technique in children when intubation attempts fail. Correctly sized bags and masks are essential to good ventilation, regardless of the provider’s skill.

A common error in pediatric bag-mask ventilation is the tendency to bag too rapidly, rather than match the rate and volume appropriate for the child’s age. On occasion, the rate or volume will need to be adjusted for the disease state. For example, lower volumes and longer expiratory times are often needed in asthma, but one must first understand the normal ventilatory parameters before adjustments can be made ( Table 111–4 ). Another common error is pressing the mask into the face in an attempt to achieve a good seal, which causes flexion of the neck and subsequent airway obstruction.