Respiratory illness, sepsis, and trauma are three important entities afflicting children that may lead to needing to manage a child’s airway. Airway management in the ED is a complex interplay of patient factors, clinical illness status, and provider factors that, through our thorough training we become proficient at navigating. We have discussed many airway concepts previously (ex, ETT Depth, Cuffed ETTs, Apneic Oxygenation, Delayed Sequence Intubation, Noninvasive Ventilation, Heliox, and Transtracheal Ventilation) but one topic that deserves specific attention is the notion of a Difficult Airway:

Difficult Airway: Basics

• Defining “Difficult Airway” is challenging, so studies are not strictly comparable (we all know it after we have dealt with it though).
• Some separate “Difficult Airway” from “Difficult Intubation.” [Belanger, 2015]
  • Difficult Airway – unable to provide adequate gas exchange despite BVM, airway adjuncts, or combination of the two.
  • Difficult Intubation – 3 or more attempts by an experienced clinician

• The incidence of difficult intubations in children vary from <0.1% to 9% [Graciano, 2014; Heinrich, 2012]
• Difficult intubations is associated with higher incidence of oxygen desaturations below 80% and adverse events. [Graciano, 2014]

Difficult Airway: Important Differences

Anatomic and physiologic differences influence how the oral, pharyngeal, and tracheal axes align as well as how the respiratory mechanics function and how the child compensates to physiologic stress.

The differences are most prominent in children < 2 years of age and more adult anatomy evolves as children progress to 8 years of age.

Anatomic Differences:

• Relatively larger head (particularly occiput)
  • Need for shoulder roll instead of head elevation to align external auditory meatus with sternal notch (which helps align the three axes).
• Smaller and compressible nasal passages
  • More easily occluded by mucous
  • Easily obstructed by poorly positioned facemask.
• Relatively larger tongue
  • More difficult to control with laryngoscope blade.
  • Occupies more mouth and posterior pharyngeal space.
• Larynx location is more cranial
  • Adult’s larynx located around C4-5
  • Child’s larynx located around C3-4, but can be even higher (C2-3).
  • Makes for more of an “anterior” airway and acute angle from pharyngeal axis to tracheal axis.
• Epiglottis is longer and more floppy
  • Softer cartilage and more pliable tissues
  • Can be more difficult to retract away from glottic opening.
• Trachea is more compressible
  • Softer cartilage and more pliable tissues
  • Can be easily compressed by a “helpful” person performing cricoid pressure (don’t let this happen).
• Ribs are horizontal
  • Contribute less to the work of breathing
  • Diaphragm does most of the work of breathing.
• Low functional residual capacity
  • Due to smaller airways and less dead space
  • Smaller reservoir from which the apneic child can draw oxygen
• Smaller number of alveoli
  • Less oxygen absorption surface area.

Physiologic Differences:

• Higher metabolic rate
  • Consumes oxygen at more than twice the adult rate
  • Combined with low functional residual capacity, leads to rapid desaturations.
• Low glycogen stores
  • High metabolic rate and low glycogen stores leads to hypoglycemia.
  • Hypoglycemia is a common SYMPTOM of the critically ill child.

Difficult Airway: Predictive Factors

• Adult-based tools (ex, LEMON, Mallampati, thyromental distance) are not predictive in young children. [Belanger, 2015]
• There are patient factors that are associated with difficult intubation. [Karsli, 2015; Belanger, 2015]
  • History of difficult airway (duh) [Graciano, 2014]
  • Less than 1 year of age
  • Signs of Upper Airway Obstruction (duh) [Graciano, 2014]
  • Congenital/Genetic Syndromes w/ altered anatomy
    • Down Syndrome
    • Pierre Robin Sequence
    • Treacher Collins
    • Cleft Palate
    • Mucopolysaccharidosis (ex, Hunter, Hurler)
  • Physiologic stress [Graciano, 2014]
    • Hypotension, ventilation failure, etc

Difficult Airway: Assume the Worst

• Most pediatric airways can be secured by experienced clinicians, but the potential for discovering a difficult airway after meds have been pushed is a perilous position to be in. [Belanger, 2015]
• Absence of predictive factors for difficult airway does not mean it will be an easy airway. [Karsli, 2016; Graciano, 2014]
  • One study found 1 in 5 Difficult Airway cases were NOT anticipated. [Karsli, 2016]

Moral of the Morsel

• Pediatric patients are a special population and warrant special considerations.
• Anatomy and Physiology matter! There are numerous differences that need to be considered… even when it is “easy.”
• Anticipate the Worst! 1 out of 5 is a concerning number – All pediatric patients should be considered to have a Difficult Airway until you successfully intubate them… then you can hit the “easy” button.
• There are no “easy airways” in the ED, regardless of age. Patients that require intubation in the ED have, be definition, stressed physiologic systems and, as such, should be considered difficult until proven otherwise.

References