Differences in upper airways of neonates, children and adults

This chapter is most relevant to Section F1(ii) from the 2017 CICM Primary Syllabus, which emplores the trainees to "understand the differences encountered in the upper airway for neonates, children and adults". Weirdly, it has never come up in the CICM Part One written exam, but the Fellowship examiners sure seem to love this topic, and it accounts for a third of all Paeds questions from the adult Part Two past papers. Examples include:

  • Question 5 from the second paper of 2014 (generally)
  • Question 27 from the first paper of 2016 (stridor)
  • Question 9 from the first paper of 2010 (generally)
  • Question 4 from the second paper of 2008 (generally)
  • Question 9 from the first paper of 2007 (generally)
  • Question 11 from the second paper of 2006 (difficult paediatric intubation)
  • Question 18 from the first paper of 2005 (generally)

Because of this increased attention in Part Two (and relative inattention in Part One), this topic is treated with some respect in the Required Reading section for Part Two exam preparation, where there is a chapter dedicated to the paediatric airway.  To simplify revision and because of chronic lazyness, the author has wrecked SEO by duplicating its contents below, with minimal modification. For the purposes of logically organising this information, it was reasonable to view the differences in terms of "infants vs. adults" because the majority of anatomical weirdness in this area is seen before the age of 12 months.

Anatomical Peculiarities of the Paediatric Airway
Anatomical problem How this is a problem
Prominent occiput Neck is flexed in the supine position. 
Laryngoscopy will be difficult in this position.
Small mandible Less anterior excursion; smaller mouth opening
Large tongue Large tongue relative to the size of the oral cavity. Causes airway obstruction and interferes with laryngoscopy.
Larger tonsils and adenoids Can cause airway obstruction. Nasopharyngeal airways may cause bleeding and aspiration.
Superior laryngeal position Located opposite the C3 to C4 vertebrae, compared with the C4 to C5 in adults. Laryngoscopy is made more difficult.
Large, floppy epiglottis The epiglottis projects further into the airway and covers more of the glottis (until the age of 4)
Short trachea Easy to intubate the right main bronchus.
Easy to inadvertently extubate the child.
Narrow trachea  More predisposed to obstruction: small decreases in the airway size will cause obstruction.
The needle or surgical cricothyroidotomy is more difficult, as the target is smaller. 
One should also be concerned about the risk of tracheal stenosis following prolonged intubation or tracheostomy.
Soft trachea and cricoid Cricoid pressure may collapse the airway
Anatomic subglottic narrowing An effective anatomic seal can be expected without the need for a cuffed ETT. Foreign bodies can become lodged below the cords. This resolves by age 10-12.

References

Heard, A. M. B., R. J. Green, and P. Eakins. "The formulation and introduction of a ‘can't intubate, can't ventilate’algorithm into clinical practice." Anaesthesia64.6 (2009): 601-608.

Stacey, Jonathan, et al. "The ‘Can't Intubate Can't Oxygenate’scenario in Pediatric Anesthesia: a comparison of different devices for needle cricothyroidotomy.Pediatric Anesthesia 22.12 (2012): 1155-1158.

Weathers E., "The Anatomy of the Pediatric Airway" 2010 -RC EDUCATIONAL CONSULTING SERVICES, INC.

Santillanes, Genevieve, and Marianne Gausche-Hill. "Pediatric airway management." Emergency medicine clinics of North America 26.4 (2008): 961-975.

HOLM‐KNUDSEN, R. J., and L. S. Rasmussen. "Paediatric airway management: basic aspects." Acta Anaesthesiologica Scandinavica 53.1 (2009): 1-9.

Cardwell, Mary, and Robert WM Walker. "Management of the difficult paediatric airway." BJA CEPD Reviews 3.6 (2003): 167-170.