Pediatric Airway Anatomy and Approach
Franklyn Cladis
INTRODUCTION
For the health care provider who is not experienced in in pediatrics, the pediatric airway can be challenging. The difficulty in airway management with this group of patients is primarily because of its differences from the adult airway. Understanding the anatomy and the physiology of the pediatric airway can help make this landscape less challenging. The objective of this chapter is to provide the essentials of pediatric airway anatomy and to provide a framework for examining this patient population.
DEVELOPMENTAL ANATOMY
Understanding the differences between the pediatric and the adult airway makes the management of these patients less challenging and safer. These differences refer to the comparison between the neonatal airway and the adult airway. The toddler’s airway is a transition zone between the neonatal and adult. The most significant differences include the size of the pediatric head, size of the tongue, position of the larynx, and shape of the epiglottis. The narrowest portion of the pediatric airway is controversial but has historically been assigned to the cricoid ring.
1. Head size—The neonate and infant heads are relatively larger than the adult head. Because of the size of the occiput, when the neonate or infant is placed supine the neck assumes a flexed position (Fig. 40-1A,B). They do not require any additional support behind the head to assume the “sniffing” position. In fact, they may need a small shoulder roll to help extend the head out of the flexed position and into the conventional “sniffing” position.
2. Tongue—The tongue is relatively large in the neonate and infant compared with the adult. This may be a factor in airway obstruction in the anesthetized pediatric patient. During anesthesia, the musculature of the oral cavity including the tongue is relaxed and the tongue may lie against the soft palate preventing oral ventilation.1 Continuous positive airway pressure, jaw thrust, and an oral airway will often relieve this obstruction. More recent evidence suggests that the tongue may not be the most common cause of airway obstruction. In an ultrasound study by Abernethy,2 the tongue did not change position after the induction of anesthesia, and the authors concluded that it might not play a significant role in airway obstruction. In addition, Mathru and others3 in adults and Litman and others4 in children demonstrated in MRI studies that the most significant narrowing and most likely site of upper airway obstruction during sedation is at the soft palate and the epiglottis.
3. Position of larynx—The position of the larynx is classically described as being more cephalad in the newborn than the adult. Negus5 described the location of the larynx at the middle of the third cervical vertebra in the preterm infant (C3), at the C3-4 interspace in the full term infant, and at the C4-5 interspace in the adult (Fig. 40-2). In an MRI study,6 the position of the hyoid bone in 15 pediatric patients aged 0 to 2 years was located at second and third cervical vertebrae (C2-3) compared with the third and fourth cervical vertebrae (C3-4) in the adult. The cephalad location of the larynx may make the laryngoscopic view more challenging because the angle from the base of the tongue to the glottic opening is more acute. This has been one reason cited for the use of straight laryngoscope blades in pediatric patients, to facilitate this view.
4. Epiglottis—The size and the position of the epiglottis are different in the pediatric patient compared with the adult. The adult’s epiglottis is typically more broad and rigid and is positioned more parallel to the trachea. The newborn epiglottis is thinner, omega shaped, and less rigid.7 Lifting the epiglottis may be more difficult with a curved blade in the vallecula in the young child. Again, the straight blade may be more effective in the pediatric patient (Fig. 40-3).
FIGURE 40-1 The large occiput in the neonate and infant places the neck in a natural flexion (A). Gently extending the neck or placing a small shoulder roll will place the head in a “sniffing” position (B).
(Courtesy of Franklyn Cladis.)
FIGURE 40-2 Position of larynx. The position of the larynx for the premature infant (7 months gestational age), full-term infant at birth, and adult. The four and half month fetus has its larynx positioned even more cephalad at C2. (From Eckenhoff JE. Some anatomic considerations of the infant larynx influencing endotracheal anesthesia. Anesthesiology. 1951;12:401-410, with permission.)
FIGURE 40-3 Larynx of an infant. Note the omega-shaped epiglottis.
FIGURE 40-4 The effects of airway edema on the resistance in the infant and the adult. The infant’s airway is significantly more compromised by a small change in airway diameter because of a larger increase in airway resistance and decrease in cross-sectional area. (From Cote CJ, Lerman J, Todres ID. A Practice of Anesthesia for Infants and Children. Saunders Elsevier; 2009, with permission.)
5. Subglottis—The cricoid cartilage has been described as the narrowest part of the pediatric airway, compared with the glottic opening in the adult. Recently this has been challenged. Litman and others in 20028 found that the most constricted part of the larynx measured on MRI in a sedated spontaneously breathing pediatric patient is the glottic opening and the immediate subvocal cord level. Dalal and others9Related posts:
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