4 Unified Airway Concept
4.1 What It Is
There are different classifications of rhinitis or “phenotypes,” such as allergic rhinitis, nonallergic rhinitis, and mixed rhinitis. There are also different types of asthma, such as allergic, nonallergic, and mixed phenotypes. These different classifications or types of rhinitis and asthma seem very similar or overlap. This similarity is vital in understanding the unified airway concept: the idea that the upper and lower respiratory tracts are linked, not just anatomically, but also through pathophysiology and mechanisms of inflammation; that inflammation in the upper respiratory tract can influence the lower respiratory tract (and vice versa) as part of a single system. This concept also helps emphasize that type I-mediated hypersensitivity is a systemic phenomenon and that allergic inflammation isn’t necessarily isolated to one area.
4.2 How Might This Work?
This concept is based on the foundation that allergic inflammation is a systemic process and that inflammatory signals and cells travel through the bloodstream from one site to another. This is best modeled in studies where an allergen is introduced into either the nasal airway (nasal challenge) or lungs (bronchial challenge), but not both at the same time. Generally, it is seen that exposing one part of the respiratory system (either upper or lower) leads to allergic inflammation in both parts.
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