Chapter 2
THE PEDIATRIC AIRWAY
Marjorie J. Arca. M.D.I. Anatomy and Physics
The pediatric airway has unique characteristics that must be considered to
optimize delivery of gas.
- The pediatric airway is small and short
Hagen - Poiseuille’s Law describes the flow of gas through a cylinder.
R = 8nL/ח^4 where n= viscosity of gas
L = length of tube
R = radius of the tube
Although children have a shorter airway, the small diameter of the airways
(↓r), is the more important determinate of flow. Consider for instance an infant with
a 4 mm airway, that decreases by 2 mm. Diameter decreases by 50% but
resistance to flow decreases by 16 (2^4 ). In comparison, an adult with an 8 mm
airway that decreases by 2 mm, the diameter decreased by 25% but flow
decreases by 3x.
- Another factor that can influence flow of gas is the density of the gas
defined by the Reynold’s number R
R = 2Vrp n < 2,000 laminar flow
n n > 4,000 turbulent flow