1. Which of the following is NOT one of the major differences between the pediatric and adult airway?
a) Pediatric glottis is more anterior and inferior than in the adult
b) The narrowest portion of the pediatric airway is in the subglottic area vs. the glottic opening in adults
c) The pediatric tongue is proportionally larger and occupies more of the pharnyx than in the adult
d) Airway edema leads to a larger change in cross sectional area in pediatric patients than adults
2. You have a patient with biphasic stridor after extubation. You give him a dose of dexamethasone and order racemic epinephrine to the bedside. You also ask your RT to bring heliox. How does heliox work in this setting?
a) Helium is lighter and thus easier to breathe than oxygen
b) Helium decreases the viscosity of the air, making it easier to breathe
c) Helium is less dense, and thus increase the likelihood of laminar vs. turbulent flow
d) Helium decreases the Reynold's number, making it easier for oxygen to diffuse across membranes
ANSWERS & EXPLANATIONS
1. A- The pediatric airway is more anterior and SUPERIOR (not inferior) than in adults. The glottis is at C1 at birth, C3 at 6 months of age, and C5-6 by adolescence. All of the other answer choices represent significant differences between the pediatric and adult airway that impact ability to access the airway, clinical manifestations of inflammation, and response to various therapies.
2. C- Helium, due to decreased density, reduces the Reynold's number, thereby helping to promote laminar flow (Reynold's number <2000) instead of turbulent or transitional flow (Reynold's number >4000 and 3000-4000, respectively). There is less airway resistance as a result of this laminar flow and thus, decreased work of breathing. The more helium, the more effective but in some patients, you may be limited in the amount of heliox you can deliver as they may require 50% FiO2 to maintain oxygen saturations. Some clinicians feel that below 60% Helium, there is little to no effect although theoretically, any helium should reduce the Reynold's number and promote improved flow dynamics. Found to improve gas exchange in patients with airway obstruction (Cheifetz 2005)