Aerosol drug delivery using heliox and nebulizer reservoirs: results from an MRI-based pediatric model

An MRI-based model of the mouth, throat, and upper airways of a 5-year-old boy is used to evaluate methods for increasing the nebulized drug dose delivered to the lungs. Four methods are considered: (1) standard nebulizer delivery with air, (2) delivery with 70/30 helium-oxygen (heliox), (3) delivery with air and an aerosol-conserving reservoir, and (4) delivery with heliox and a reservoir. When comparing air and heliox, delivery flowrates were adjusted so that the aerosols produced were of similar size. The reservoir utilized was the Medicator Aerosol Maximizer (Healthline Medical, Baldwin Park, CA). It conserves the aerosol generated by the nebulizer during exhalation and makes it available for the next inhalation. Technetium-DTPA was utilized. The standard nebulizer driven by air delivered 2.2% of the dose loaded into the nebulizer to the lungs as fine droplets, versus 3.3% for the nebulizer with heliox (50% increase; p = 0.002 vs. air), 2.9% for the nebulizer plus reservoir driven by air (32% increase; p = 0.02 vs. no reservoir), and 4.0% for the nebulizer plus reservoir driven by heliox (82% increase; p = 0.002 vs. air without reservoir). The increased pulmonary dose when heliox was utilized occurred because of decreased deposition within the nebulizer and other delivery equipment. The increased pulmonary dose when the reservoirs were utilized occurred due to a decrease in the dose expelled from the nebulizer by exhalation.