There is a sensory system within the mucosa of the nose and supraglottic larynx that appears to be both mechanosensitive and chemosensitive. Our data suggest that the respiratory modification produced by microaerosol inhalation represents a mechanoreceptor rather than chemoreceptor response. Furthermore, the sensitivity of this reflex system appears aged-dependent, the data indicating a more active response early in life. From a clinical perspective, it is postulated that aerosol inhalation reflex alters the pattern of breathing, resulting in improved respiratory flow rates during partial upper airway obstruction. The mechanism of a favorable clinical response to mist inhalation has not been previously appreciated in this context.