Cross Section of Airway Wall
The radius of the airway lumen is determined by the level of ...
High
Low
Muscle Contraction
Airway Wall Inflammation
Mucus Secretion
0
2
4
6
8
10
and the dose & type of asthma medication ...
High
Low
0
2
4
6
8
10
Reliever
Preventer (prophylactic)
Preventer (acute)

 

As the radius of the airway lumen decreases (airway narrowing), airway resistance (R) increases because:

Airway Resistance ∝ 1/radius⁴

Pousielle's Law describing airflow through a tube

Lumen Radius
Airway Resistance (arbitrary units)
Airway Resistance ∝ 1/radius⁴
0
2
4
6
8
10