The size and behavior of the human upper airway during inhalation of aerosols

ABSTRACT
Introduction: The mouth, the pharynx and the larynx are potential sites of aerosol deposition in the
upper airway during inhalation of aerosolized drugs. The right angle bend of the lumen at the back of
the mouth, the position of the tongue, the variable size and shape of the lumen in the pharynx and the
larynx, and the breathing pattern could increase aerosol deposition in the upper airway and decrease
lung deposition.
Areas covered: In this review, the anatomy of the upper airway from the oral cavity to the glottis and
the impact of mandibular protrusion and incisal opening on the size of the upper airway are highlighted.
In addition, the impact of inhalation maneuvers, inhaler mouthpiece geometries and a stepped
mouthpiece on the size of the upper airway are discussed.
Expert opinion: The structure of the upper airway lumen does not have a fixed cross sectional area and
is susceptible to both constriction and distension during inhalation. The size of the upper airway can be
enlarged through mandibular protrusion and/or incisal opening which might decrease aerosol deposition
in the upper airway and increase lung deposition.