The effects of preferential deposition of histamine in the human airway.

Two inhalation techniques were performed to obtain airway and diffuse airway deposition of histamine aerosol. A radiotracer method was used to confirm the patterns of aerosol deposition and to measure the dose of histamine aerosol in the airways. In 5 subjects the effect of cumulative doses of histamine aerosol given either centrally or diffusely to the airways was measured. Histamine aerosol deposited predominantly in the large airways was more effective in increasing airway obstruction that was diffusely deposited histamine aerosol, suggesting that the receptors mediating the action of histamine reside mainly in the large airways.