Emergency airway management in children: Unique pediatric considerations

INTRODUCTION — The anatomic structures and physiologic processes that affect the assessment and management of the airway in children will be reviewed here as will the challenge of achieving proficiency for practitioners who infrequently perform pediatric airway management. Specifics regarding airway management techniques are discussed separately. (See "Basic airway management in children" and "Technique of emergency endotracheal intubation in children" and "Rapid sequence intubation (RSI) in children for emergency medicine: Approach".)

ANATOMIC CONSIDERATIONS — There are several anatomic features in infants and children that may impact advanced airway management. Here we discuss the relevant structures and their effect on airway management.

Prominent occiput — The proportionally larger occiput in infants and younger children causes varying degrees of neck flexion in the supine position. This can result in anatomic airway obstruction or interfere with attempts to visualize the glottic opening during laryngoscopy [1-3]. Placing a towel roll under the shoulders in young infants can improve airway alignment (picture 1). This approach is in contrast to placing a pad under the occiput in adults.

Large tongue — Infants and young children have large tongues relative to the size of the oral cavity. Therefore, inadequate control and displacement of the tongue may impede visualization of the deeper airway during direct laryngoscopy. In addition, the tongue becomes a common source of upper airway obstruction, particularly in patients with depressed mental status and concomitant loss of intrinsic airway tone. Retroglossal obstruction occurs in approximately half of obstructions in infants, compared with adults where the vast majority of intrinsic airway obstruction occurs at the level of the soft palate [4,5].

Larger tonsils and adenoids — Children more commonly have larger tonsils and adenoids than adults. Studies utilizing magnetic resonance imaging (MRI) have confirmed that this increased mass of lymphoid tissue contributes to airway obstruction in children [6]. In addition, adenoidal bleeding can occur with placement of a nasopharyngeal airway or attempts at nasotracheal intubation. Resultant blood in the naso- and hypopharynx can lead to aspiration and make glottic visualization challenging.

Superior laryngeal position — The position of the larynx in infants and children is more cephalad than in adults. It is located opposite the C3 to C4 vertebrae, compared with the C4 to C5 in adults (figure 1) [7,8]. This creates a more acute angle between the glottic opening and the base of the tongue, which can make direct visualization more challenging.

Weaker hyoepiglottic ligament — As the name indicates, the hyoepiglottic ligament connects the hyoid bone to the epiglottis, running through the base of the vallecula. Applying direct tension to the ligament can elevate the epiglottis and improve glottic visualization. In young children, it has less tensile strength; therefore, in some patients, curved blades designed for tip placement in the vallecula (eg, Macintosh) may not elevate the epiglottis as effectively as in adults.

Large, floppy epiglottis — The epiglottis is relatively large and floppy in children, particularly those younger than three years of age. It is also angled more acutely with respect to the axis of the trachea. As a result, the epiglottis projects into the airway and covers more of the glottic aperture (figure 1). Effective mobilization of the epiglottis also favors the use of a straight blade to directly lift the epiglottis to provide visualization during direct laryngoscopy (figure 2). Infants and young children may have an omega-shaped epiglottis that can lead to positional, inspiratory stridor and can give the appearance of a thickened epiglottis on lateral airway radiographs [9].

Shorter trachea — The trachea increases in length with age, from approximately 5 cm in neonates to 12 cm in adults [10,11]. The short trachea predisposes to right mainstem bronchus intubation or inadvertent extubation, given the short segment within which an endotracheal tube (ETT) can be correctly placed [12]. This can occur at the time of intubation, or during unintentional head movement, which has been shown to displace ETTs as much as 1 cm in neonates and 2 cm in older children [13].

Narrow trachea — In addition to being shorter in length, the trachea in younger children is also narrow [10,11]. Because airway resistance is inversely proportional to the lumen radius to the fourth power, even small decreases in the size of the airway lumen from secretions, edema, or external compression (including external laryngeal manipulation, in circumstances in which it is felt to be beneficial) will have disproportionate effects on these smaller airways (figure 3). The narrow tracheal lumen, combined with the narrow space between tracheal rings and small size of the cricothyroid membranes, makes needle or surgical cricothyroidotomy technically challenging in infants and children [14]. (See "The difficult pediatric airway for emergency medicine".)

Anatomic subglottic narrowing — In adults, the vocal cords comprise the narrowest portion of the airway. Historically, the cricoid ring has been identified as the narrowest portion of the pediatric airway in cadaveric studies [15]. More recent data suggest that the airway in children may not be conical or funnel-shaped as previously believed. Measurements taken during magnetic resonance imaging (MRI) and bronchoscopy show that the cross sectional area is smaller at the vocal cords than the subglottis [16,17]. Similarly, airway imaging using MRI and computed tomography including both cross sectional and three-dimensional reconstructions show no difference in the cross sectional area between the subglottis and the cricoid ring. The shape of the cricoid ring does change with age, with an elliptical shape in infants and evolving to a circular shape similar to adults in older children [16,18-20].

As a result of the elliptical shape of the subglottis and cricoid cartilage, particularly in infants, foreign bodies can become lodged below the cords, and resistance during endotracheal tube (ETT) passage may increase at this level. Cuffed ETTs can effectively fill the elliptical shape of the subglottic airway and reduce the likelihood of air leak around the tube. With the advent of newer, smaller profile, lower pressure cuffed tubes, the American Heart Association initially approved cuffed ETTs for all pediatric patients outside the newborn period in 2010 and more recently has suggested that cuffed tubes may be chosen over uncuffed tubes, provided the cuff pressure can be maintained at less than 20 cm H₂O [21,22]. In addition, use of a cuffed ETT in children is associated with a reduced need for ETT exchanges and no increase in post-extubation morbidity or long-term complications when compared to uncuffed tubes. (See "Technique of emergency endotracheal intubation in children", section on 'Cuffed versus uncuffed'.)

Compliant chest wall — The thoracic skeleton in children is primarily cartilaginous and therefore more compliant than the ossified bony structures in adults [23]. Intrinsic muscle tone is required to maintain lung volumes and prevent chest wall distortion. Therefore, infants and young children are more likely to experience respiratory muscle fatigue, atelectasis and respiratory failure.

PHYSIOLOGIC CONSIDERATIONS — Age-specific physiologic features in infants and children can also affect advanced airway management. Here we discuss those processes which are different in children, and how they impact assessment and management of the pediatric airway.

Age-related respiratory rate — Normative ranges for vital signs vary by age (table 1). Variation in patterns may also occur, such as periodic breathing which occurs commonly in the first six months of life [24]. Discriminating normal from concerning vital sign values and trends is paramount in assessing respiratory illness and response to therapy.

Preferential nasal breathing — Infants are commonly believed to be obligate nasal breathers. Some data suggest that a subset of infants will fail to initiate mouth breathing within a prescribed time after nasal occlusion [25]; however, others have shown infants can breathe through their mouths spontaneously or following nasal airflow obstruction [26,27]. For the majority of infants who are nasal breathers, the nares account for nearly half the total airway resistance [28]. Therefore, obstruction by secretions, edema, or compression from non-flowing nasal cannula or a misplaced face mask can lead to significant increase in the work of breathing.

Smaller tidal volumes — Infants and young children have small, relatively fixed tidal volumes relative to body size (6 to 8 mL/kg). As a result, they are susceptible to iatrogenic barotrauma from aggressive positive pressure ventilation. In addition, the limited ability to increase minute ventilation with deeper breathing means that any compensatory response to physiologic demands for increased minute volume is most likely to be manifest as tachypnea. Limited sustainability of rapid respiratory rates predisposes young infants to respiratory failure.

Lower functional residual capacity — Functional residual capacity (FRC) increases with age during childhood [29,30]. Therefore, young children have little intrapulmonary oxygen stores to utilize during hypoventilatory or apneic periods. Apneic infants and toddlers, in particular, have a more precipitous decline in oxygen saturation, for example, when they undergo rapid sequence intubation [31,32]. For this reason, children have a heightened need for preoxygenation and, possibly, bag-mask ventilation during rapid sequence induction for intubation. (See "Rapid sequence intubation (RSI) in children for emergency medicine: Approach", section on 'Preoxygenation'.)

Higher oxygen metabolism — Infants have a higher metabolic rate and consume oxygen at a rate twice that of adults (6 versus 3 mL/kg/min) [33,34]. This higher oxygen consumption, coupled with the lower FRC in children, results in a shorter safe apnea time. In a study of preoxygenated ASA I children (ie, healthy, no medical problems), the mean time to oxygen desaturation to 90 percent ranged from 1.5 minutes in children less than six months to more than six minutes in children greater than 11 years of age [31].

Prone to respiratory fatigue — Infants and younger children have a lower percentage of efficient, slow-twitch (type 1) skeletal muscle fibers in their intercostal muscles than older patients [33]. Therefore, when children utilize retractions to facilitate airflow during respiratory distress, they are more prone to fatigue, and ultimately, respiratory failure.

Higher vagal tone — Infants and young children may have a pronounced vagal response to laryngoscopy or airway suctioning. Because hypoxia potentiates the risk for bradycardia, efforts to maintain oxygenation before and during endotracheal intubation should be maximized.

The role for atropine in preventing bradycardia during airway management is discussed elsewhere. (See "Rapid sequence intubation (RSI) in children for emergency medicine: Approach", section on 'Pretreatment'.)

LIMITED OPPORTUNITY TO GAIN PROFICIENCY — Laryngoscopy and endotracheal intubation are complex psychomotor skills that require sufficient training and practice to achieve and maintain proficiency. Studies including neonatal, pediatric, and adult populations have shown that intubation success increases by level of training [34-37]. As an example, in an observational study that evaluated first-time success rates for 114 pediatric rapid sequence intubations in children’s hospital emergency departments, pediatric emergency medicine attendings had a higher first-time success rate (89 percent) than pediatric emergency medicine fellows (43 percent) or pediatric residents (35 percent) [37]. More specifically, learning curves for anesthesia resident clinicians in a controlled setting showed that after 10 intubations the success rate was less than 50 percent, and only after 57 intubations did these trainees achieve a 90 percent success rate [38]. For non-anesthesia trainees, success also increased with experience, with a predicted 90 percent rate of "good" intubations achieved after 47 prior attempts [39].

In pediatrics, advanced airway management experience for many providers outside of anesthesia may be limited [40]. Comparing data from pediatric and adult tertiary care emergency departments, health care providers have less frequent opportunities to perform intubation in children than in adults. A survey of pediatric emergency departments suggests a range of 1.1 to 3.3 intubations per 1000 patients per year [41], while studies based in adult facilities demonstrate 6 to 10 intubations per 1000 patients per year [42,43]. This demonstrated need for extensive experience, in contrast to the infrequent opportunities to perform advanced airway techniques in children, also needs to be considered in pediatric airway management. Simulation training can provide an alternative means for pediatric airway management training [44].

Rescue ventilation devices such as the laryngeal mask airway or laryngeal tube provide alternatives to endotracheal intubation, and are more likely to be placed correctly than endotracheal tubes by providers with limited prior experience [45-50]. Thus, health care providers who will be involved in airway management should develop comfort and familiarity with at least one rescue ventilation device. (See "Supraglottic airway devices in children with difficult airways".)

SUMMARY

●Pediatric versus adult airway – Although the indications for airway management in children are similar to those in adults, unique pediatric anatomy and physiology create specific challenges in assessment and management:

•Anatomy – Pediatric anatomy (figure 1) predisposes to airway obstruction and significantly impacts pediatric airway management, including (see 'Anatomic considerations' above):

-Relatively larger oropharyngeal structures (tongue, tonsils, and adenoids)

-Large floppy epiglottis with greater difficulty in visualizing the vocal cords during laryngoscopy

-Proportionally larger occiput in infants and younger children causes neck flexion and potential airway obstruction in the supine position (picture 1)

-shorter and narrower trachea increases risk of endotracheal tube malposition after intubation.  

•Physiology – Several unique physiologic differences negatively impact airway management in infants and children (see 'Physiologic considerations' above):

-Because of decreased functional residual capacity and increased oxygen consumption, they become hypoxemic more quickly than adults. These physiologic differences result in a shorter and less safe apnea time during rapid sequence intubation (RSI).

-A majority of infants primarily breath through their nose and can have compromised respiratory status caused by nasal obstruction, edema, or compression.

-Infants and young children have a pronounced vagal response with bradycardia in response to laryngoscopy or airway suctioning

-Infants and younger children have a lower percentage of efficient, slow-twitch (type 1) skeletal muscle fibers in their intercostal muscles and are more prone to fatigue and respiratory failure.

•Maintenance of skills – Developing competence and maintaining proficiency with advanced airway management is particularly challenging in children because of the relative infrequency with which most practitioners utilize these skills. Simulation training can provide an alternative means for airway management training. (See 'Limited opportunity to gain proficiency' above.)