Single-breath deposition of jet-nebulized saline aerosol

A common method of inhalation of aerosols used in clinical research and in therapy is by single inspiratory breaths at unregulated inspiratory flow rates from a jet-type nebulizer. We have studied the effect of inspiratory flow rate on the regional deposition of such an orally inhaled aerosol when delivered to the human respiratory tract directly from a jet-type nebulizer by single inspiratory breaths. The aerosol, generated by a No.42 DeVilbiss jet nebulizer, was inhaled by mouth by three normal human subjects at flow rates between 13 and 165 1/min. At mean inspiratory flow rates ranging between 13 and 35 1/min, deposition of the radioaerosol was predominantly in the bronchopulmonary region (larynx and below) of the three subjects. Inhalation of the aerosol at flow rates above 48 1/min resulted in increasing oropharyngeal deposition (supralaryngeal). Oropharyngeal deposition of the aerosol, at all inspriatory flow rates, was greater than predicted by the Stokes number calculated using the inspiratory flow rate. The reason for this enhanced deposition is believed to be the direct jetting of particles onto the oropharyngeal wall.