Detecting airway obstruction
Airway obstruction may be present
during inspiration and during expiration. It may be
due to abnormalities in ‘upper airways’ (from
the nose and mouth up to and including the extrathoracic
trachea) and in ‘lower airways’ (all airways
within the thorax). Obstruction in upper airways can
sometimes be detected from forced inspiratory
maneuvers, whilst forced expiratory maneuvers are required
to disclose obstruction in lower airways. Why this
is so is explained in this section.
A synopsis of the effect of forced inspiratory and expiratory maneuvers on airway calibre, and hence on flows, is shown in the animation.