Not little adults: The uniqueness of the pediatric airways
Learn the differences between adult and pediatric airways.
The following is paid content sponsored by Ambu.
By Jonathan Lee for EMS1 BrandFocus
Kids are not little adults. Everyone has heard this cliché, but why is it so common and what does it mean in terms of pediatric airways?
While it is true that pediatric airways are absolutely smaller than their adult counterparts, there also are important differences in structure and function that affect the way the airway is managed.
Being aware of these differences is imperative in managing any child under two years of age.
KIDS ARE SHAPED DIFFERENTLY.
In newborns, the development of the skull is still a dynamic process. Their head is relatively larger in proportion to their body.
This large occiput displaces the airways in a different direction than in older children and adults. The tongue also is relatively large, meaning the amount of space in the oropharynx is decreased.
The nares of a child tend to be more restrictive than an adult. This is a result of its absolute smaller size when compared, as well as having relatively more mucousal tissue, which reduces the internal diameter of the passage.
Additionally, larger nasal tonsils (adenoids that will eventually atrophy) as well as an increased likelihood of hypertrophied nasal turbinates contribute to overcrowding in the nasopharynx.
Structural differences continue in the larynx. The glottis is much higher (cephalic) in children. In newborns, it can be as high C1, descending to approximately C3-C4 by age seven before reaching its adult position at C4-C5 (Wall).
The shape of the larynx also is different. Traditional teaching suggested that the narrowest portion of the trachea in children was at the level of the cricoid ring. While functionally this may remain true, recent research indicates that the glottis might be anatomically the narrowest point as it is in adults
KIDS WORK DIFFERENTLY.
A number of important physiological differences also exist.
First, kids have a reduced functional residual capacity compared to adults. Metabolically, children are much more active than adults. Oxygen consumption may be as much as doubled in kids, 6ml/kg/min versus 3ml/kg/min in adults.
Finally, there also is a corresponding increase in C02 production; adults producing an average of 60ml/kg/min compared to 150ml/kg/min in children.
This increased C02 production is the physiologic rationale for the increased respiratory rate, which is normal in children. The combination of higher basal metabolic rate and decreased functional residual capacity explains why children desaturate much more quickly than adults.
The consequences of these physiological changes become significant when children are exposed to painful or frightening stimulus. The work of breathing associated with crying can increase by a factor of 32, placing an ill child at risk of dynamic airway obstruction or respiratory arrest
KIDS NEED TO BE MANAGED DIFFERENTLY.
What do these differences mean in practical terms? In the Manual of Emergency Airway Management, Walls makes several recommendations specific to managing children including the following:
Appreciating the speed with which kids can desaturate as well as identifying work of breathing as a risk factor are both key. Supplemental oxygen can be supplied with appropriate sized nasal cannula, simple face masks or non-rebreather masks. (A BVM is not appropriate for a spontaneously breathing patient unless it is being used to provide assisted ventilation; a BVM does not otherwise provide free flow oxygen.)
For BVM ventilation
Effective bag valve mask ventilation is the cornerstone of all airway management, and it is especially important in children. The absolute size of a child’s anatomy requires appropriate sized BVM both to ensure an adequate mask seal as well as to prevent hyperinflation from supra-physiological tidal volumes. Head placement is critical. Hyperextension and hyperflexion of the neck can both cause anatomical obstruction of the airway. A slight sniffing position will help prevent the tongue from obstructing the airway by falling against the posterior pharynx. A towel roll under the shoulders is frequently necessary in young children to offset the flexion caused by the large occiput.
For direct laryngoscopy, straight blades are generally more successful for navigating the pediatric tongue and epiglottis. Uncuffed endotracheal tubes were traditionally used to seal at the cricoid ring; cuffed endotracheal tubes have become more widely used to avoid airway leak. Large, easily traumatized tonsils and adenoids, combined with the acute angle between the laryngeal opening and epiglottis make blind nasal intubation inadvisable in children.
For surgical airways
The size of the cricothyroid membrane ranges from small to non-existent in children, making needle cricothyrotomy very difficult and surgical crycothyrotomy nearly impossible in small children.
Children under two years are physiologically different from adults. Keep the above in mind whenever treating these patients.