Differentiating Aspects of the Pediatric Airway

Robert C. Luten

Nathan W. Mick

THE CLINICAL CHALLENGE

Airway management in the pediatric population presents many potential challenges, including age-related drug dosing and equipment sizing, anatomical variation that continuously evolves as development proceeds from infancy to adolescence, and the performance anxiety that invariably accompanies the resuscitation of a critically ill child. Clinical competence in managing the airway of a critically ill or injured child requires an appreciation of age- and size-related factors, and a degree of familiarity and comfort with the fundamental approach to pediatric airway emergencies.

The principles of airway management in children and adults are the same. Medications used to facilitate intubation, the need for alternative airway management techniques, and the basic approach to performing the procedure are similar whether the patient is 8 or 80 years of age. There are, however, a few important differences that must be considered in emergency airway management situations. These differences are most exaggerated in the first 2 years of life, after which the pediatric airway gradually develops more adult-like features.

APPROACH TO THE PEDIATRIC PATIENT

General Issues

A recent review of the pediatric resuscitation process attempted to define elements of the mental (cognitive) burden of providers, when dealing with the unique aspects of critically ill children compared with adults. Age- and size-related variables unique to children introduce the need for more complex, nonautomatic, or knowledge-based mental activities, such as calculating drug doses and selecting equipment. The concentration required to undertake these activities while under stress may subtract from other important mental activity such as assessment, evaluation, prioritization, and synthesis of information, referred to in the resuscitative process as critical thinking activities. The cumulative effect of these factors leads to inevitable time delays and a corresponding increase in the potential for decision-making errors in the pediatric resuscitative process. This is in sharp contrast to adult resuscitation, where drug doses, equipment sizing, and physiologic parameters are usually familiar to the provider, leading to more automatic-type decisions that free the adult provider’s attention for critical thinking. In children, drug doses are based on weight and may vary by an order of magnitude depending on age (i.e., 3-kg neonate vs. a 30-kg 8-year-old vs. a 100-kg adolescent). The use of resuscitation aids in pediatric resuscitation significantly reduces the cognitive load (and error) related to drug dosing calculations and equipment selection by relegating these activities to a lower order of mental function (referred to as “automatic” or “rule based”). The results are reduced error, attenuation of psychological stress, and an increase in critical thinking time. Table 24-1 is a length-based, color-coded equipment reference chart (Broselow-Luten-based “resuscitation guide”) for pediatric airway management that eliminates error-prone strategies based on age and weight. Both equipment and drug dosing information are included in the Broselow-Luten system and can be accessed by a single length measurement or patient weight. This system is also available as part of a robust online resource (www.ebroselow.com).

Specific Issues

Anatomical and functional issues

The approach to the child with airway obstruction (the most common form of a difficult pediatric airway) incorporates several unique features of the pediatric anatomy.

1. Children obstruct more readily than adults do and the pediatric airway is especially susceptible to airway obstruction resulting from swelling. See Table 26-4 that outlines the effect of 1-mm edema on airway resistance in the infant (4-mm airway diameter) versus the adult (8-mm airway diameter). Nebulized racemic epinephrine causes local vasoconstriction and can reduce mucosal swelling and edema to some extent. For diseases such as croup, where the anatomical site of swelling occurs at the level of the cricoid ring, the narrowest part of the pediatric airway, racemic epinephrine can have dramatic results. Disorders located in areas with greater airway caliber, such as the supraglottic swelling of epiglottitis or the retropharyngeal swelling of an abscess, rarely produce findings as dramatic. In these latter examples, especially in epiglottitis, efforts to force a nebulized medication on a child may agitate the child, leading to increased airflow velocity and dynamic upper airway obstruction.

TABLE 24-1 Equipment Selection

	Pink^a	Red	Purple	Yellow	White	Blue	Orange	Green
Length (cm)-based pediatric equipment chart
Weight (kg)	6-7	8-9	10-11	12-14	15-18	19-23	23-31	31-41
Length (cm)	60.75-67.75	67.75-75.25	75.25-85	85-98.25	98.25-110.75	110.75-122.5	122.5-137.5	137.5-155
ETT size (mm)	3.5	3.5	4.0	4.5	5.0	5.5	6.0 cuff	6.5 cuff
Lip-to-tip length (mm)	10-10.5	10.5-11	11-12	12.5-13.5	14-15	15.5-16.5	17-18	18.5-19.5
Laryngoscope size+blade	1 straight	1 straight	1 straight	2 straight	2 straight	2 straight or curved	2 straight or curved	3 straight or curved
Suction catheter	8F	8F	8F	8-10F	10F	10F	10F	12F
Stylet	6F	6F	10F	10F	10F	10F	14F	14F
Oral airway (mm)	50	50	60	60	60	70	80	80
Nasopharyngeal airway	14F	14F	18F	20F	22F	24F	26F	30F
Bag/valve device	Infant	Infant	Child	Child	Child	Child	Child/adult	Adult
Oxygen mask	Newborn	Newborn	Pediatric	Pediatric	Pediatric	Pediatric	Adult	Adult
Vascular access	22-24/23-25	22-24/23-25	20-22/23-25	18-22/21-23	18-22/21-23	18-20/21-23	18-20/21-22	16-20/18-21
Catheter/butterfly	Intraosseous	Intraosseous	Intraosseous	Intraosseous	Intraosseous	Intraosseous
NG tube	5-8F	5-8F	8-10F	10F	10-12F	12-14F	14-18F	18F
Urinary catheter	5-8F	5-8F	8-10F	10F	10-12F	10-12F	12F	12F
Chest tube	10-12F	10-12F	16-20F	20-24F	20-24F	24-32F	24-32F	32-40F
BP cuff	Newborn/infant	Newborn/infant	Infant/child	Child	Child	Child	Child/adult	Adult
LMA^b	1.5	1.5	2	2	2	2-2.5	2.5	3
Directions for use: (1) measure patient length with centimeter tape or with a Broselow tape; (2) using measured length in centimeters or Broselow tape measurement, access appropriate equipment column; (3) column for ETTs, oral and nasopharyngeal airways, and LMAs; always select one size smaller and one size larger than recommended size.
^aFor infants smaller than the pink zone, but not preterm, use the same equipment as the pink zone. ^bBased on manufacturer’s weight-based guidelines:
Mask size Patient size (kg)
1 ≤5
1.5 5-10
2 10-20
2.5 20-30
3 >30
Permission to reproduce with modification from Luten RC, Wears RL, Broselow J, et al. Managing the unique size related issues of pediatric resuscitation: reducing cognitive load with resuscitation aids. Ann Emerg Med. 1992;21:900-904.

2. Noxious interventions can lead to dynamic airway obstruction and precipitate respiratory arrest, leading to the admonition to “leave them alone.” The work of breathing in the crying child increases 32-fold, elevating the threat of dynamic airway obstruction and hence the principle of maintaining children in a quiet, comfortable environment during evaluation and management for upper airway obstruction (Fig. 24-1A-C).

3. Bag-mask ventilation (BMV) may be of particular value in the child who has arrested from upper airway obstruction. Note in Figure 24-1C that efforts by the patient to alleviate the obstruction may actually exacerbate it, as increased inspiratory effort creates increased negative extrathoracic pressure, leading to collapse of the malleable extrathoracic trachea. The application of positive pressure through BMV causes the opposite effect by stenting the airway open and relieving the dynamic component of obstruction (Fig. 24-1C,D). This mechanism explains the recommendation to try BMV as a temporizing measure, even if the patient arrests from obstruction. There have been numerous case reports of children with epiglottitis successfully resuscitated utilizing BMV.

4. Apart from differences related to size, there are certain anatomical peculiarities of the pediatric airway. These differences are most pronounced in children <2 years of age, whereas children >8 years of age are similar to adults anatomically and the 2- to 8-year-old period is one of transition. The glottic opening is situated at the level of the first cervical vertebra (C-1) in infancy. This level transitions to the level of C-3 to C-4 by age 7 and to the level of C-5 to C-6 in the adult. Thus, the glottic opening tends to be higher and more anterior in children as opposed to adults. The size of the tongue with respect to the oral cavity is larger in children, particularly infants. The epiglottis is also proportionately larger in a child making efforts to visualize the airway with curved blade by insertion of the blade tip into the vallecula and lifting the epiglottis out of the way more difficult. Thus a straight blade, which is used to directly lift the epiglottis up, is recommended in children younger than 3 years (Table 24-2).

Blind nasotracheal intubation is relatively contraindicated in children younger than 10 years for at least two reasons: Children have large tonsils and adenoids that may bleed significantly when traumatized, and the angle between the epiglottis and the laryngeal opening is more acute than that in the adult, making successful cannulation of the trachea difficult.

Children possess a small cricothyroid membrane and in children younger than 3 to 4 years, it is virtually nonexistent. For this reason, needle cricothyrotomy may be difficult, and surgical cricothyrotomy is virtually impossible and contraindicated in infants and small children up to 10 years of age.

Although younger children possess a relatively high, anterior airway with the attendant difficulties in visualization of the glottic aperture, this anatomical pattern is consistent from one child to another, so this difficulty can be anticipated. The adult airway is subject to more variation and age-related disorders leading to a difficult airway (e.g., rheumatoid arthritis, obesity, etc.). Children are predictably “different” not “difficult.” Figure 24-2 demonstrates anatomical differences particular to children.

Physiologic issues

There are two important physiologic differences between children and adults that impact airway management (Box 24-1). Children have a basal oxygen consumption that is approximately twice that of adults. Coupled with a proportionally smaller functional residual capacity (FRC) to body weight ratio these factors result in more rapid desaturation in children compared with adults given an equivalent duration of preoxygenation. The clinician must anticipate and communicate this possibility to the staff and be prepared to provide supplemental oxygen by BMV if the patient’s oxygen saturation drops below 90%.

Figure 24-1 • Intra- and Extrathoracic Trachea and the Dynamic Changes that Occur in the Presence of Upper Airway Obstruction. A: Normal anatomy. B: The changes that occur with normal inspiration; that is, dynamic collapsing of the upper airway associated with the negative pressure of inspiration on the extrathoracic trachea. C: Exaggeration of the collapse secondary to superimposed obstruction at the subglottic area. D: Positive-pressure ventilation (PPV) stents the collapse/obstruction versus the patient’s own inspiratory efforts, which increase the obstruction. (Adapted from Cote CJ, Ryan JF, Todres ID, et al., eds. A Practice of Anesthesia for Infants and Children. 2nd ed. Philadelphia, PA: WB Saunders; 1993, with permission.)

TABLE 24-2 Anatomical Differences between Adults and Children

Anatomy	Clinical significance
Large intraoral tongue occupying relatively large portion of the oral cavity and proportionally larger epiglottis	Straight blade preferred over curved to push distensible anatomy out of the way to visualize the larynx and elevate the epiglottis
High tracheal opening: C-1 in infancy vs. C-3 to C-4 at age 7, C-5 to C-6 in the adult	High anterior airway position of the glottic opening compared with that in adults
Large occiput that may cause flexion of the airway, large tongue that easily collapses against the posterior pharynx	Sniffing position is preferred. The larger occiput actually elevates the head into the sniffing position in most infants and children. A towel may be required under shoulders to elevate torso relative to head in small infants
Cricoid ring is the narrowest portion of the trachea as compared with the vocal cords in the adult	Uncuffed tubes provide adequate seal because they fit snugly at the level of the cricoid ring Correct tube size essential because variable expansion cuffed tubes not used
Consistent anatomical variations with age with fewer abnormal variations related to body habitus, arthritis, chronic disease	Younger than 2 y, high anterior; 2-8 y, transition; and older than 8 y, small adult
Large tonsils and adenoids may bleed; more acute angle between epiglottis and laryngeal opening results in nasotracheal intubation attempt failures	Blind nasotracheal intubation not indicated in children; nasotracheal intubation failure
Small cricothyroid membrane landmark, surgical cricothyrotomy impossible in infants and small children	Needle cricothyrotomy recommended and the landmark is the anterior surface of the trachea, not the cricoid membrane