Oropharyngeal deposition and delivery aspects of metered-dose inhaler aerosols.

Oropharyngeal deposition and subsequent delivery of metered-dose inhaler (MDI) aerosols into the lung were measured with the actuator alone and with 4 different kinds of auxiliary devices; open-end straight tube, Aerochamber, Nebuhaler, and InspirEase. The total mass of dry aerosol discharged directly from the actuator, from the auxiliary devices, and through the oropharyngeal model was determined by collecting the aerosol on the absolute filter and weighing the filter. Aerosol depositions in the auxiliary devices and in the oropharynx as well as the amount of aerosol delivered past the oropharynx were determined as percentages of the total aerosol mass output from the actuator alone. Six different MDI aerosols, 3 bronchodilators, and 3 corticosteroids were used. With the actuator alone, oropharyngeal deposition ranged from 33 to 71% at an inspiratory flow rate of 0.33 L/s, depending on the type of MDI aerosols. Aerosol delivery into the lung was 29 to 67%. With the auxiliary devices, oropharyngeal deposition markedly decreased to the range below 6% regardless of the type of auxiliary device and aerosol. A major deposition (23 to 72%) occurred in the auxiliary devices except for Nebuhaler in which a much reduced deposition (8 to 18%) occurred. Aerosol delivery into the lung was in the range of 40 to 72% with the open-end tube, 26 to 62% with the Aerochamber, 34 to 60% with InspirEase, and 31 to 92% with Nebuhaler. Although a substantial increase in aerosol delivery (as much as 38%) was found with a large size Nebuhaler, the aerosol delivery with other smaller auxiliary devices used was comparable to those obtained without the auxiliary devices.