GENERATION OF CONCENTRATED AEROSOLS FOR INHALATION STUDIES

A technique is described for generation of concentrated respirable aer osols and their administration to canine lungs. The functional charact eristics of the system were delineated using aqueous solutions of diso dium fluorescein (DF). The aerosol was generated by delivering pressur ized air and disodium fluorescein solution to a Turbotac jet nebulizer . The particles were dried with a sheath of warm air and concentrated using a seven orifice virtual impactor. The input aerosol particles we re concentrated up to eight times, resulting in output aerosol concent ration of about 10 mg m-3 at a flow rate of 20 1 min-1. The particles had predictable mass median aerodynamic diameters between 4 and 7 mum, and geometric standard deviations between 1.7 and 2.0. To conduct inh alation studies on beagle dogs, the aerosol generation and concentrati on system was pressurized to 18 cm of water. In these experiments the test aerosol consisted of a mixture of disodium fluorescein with techn etium-99m tagged to iron oxide colloid, controlled delivery of the aer osol to the dogs was achieved by sequencing low resistance solenoid va lves using a logic control box. The animals were anesthetized and endo tracheally intubated. The aerosols were carried in the ventilating air stream. The duration of exposure was 3 min. Gamma scintigraphy confir med deposition of the aerosol in the lower lungs as demonstrated by a total lung retention between 70 and 75% after 24 h. This methodology i s applicable for use with solutions and/or colloidal suspensions and c an be adapted for continuous aerosol generation and delivery.