A drying chamber for use with small volume jet nebulizers

Abstract

Jet nebulizers are used to deliver a variety of drugs to the lower respiratory tract. The majority of droplets generated during the initial atomization process are too large to penetrate into the lower airways and hence baffles within nebulizers are used to generate droplets that fall within the ‘respirable range’ of l-5 pm (1). In certain situations such as the ‘alveolar targeting’ of drugs such as pentamidine (2), it is desirable to generate droplets <3,~rn in size. The use of such aerosols may also be useful in the treatment of patients with a variety of chronic obstructive airways diseases. It is known that for patients with cystic fibrosis and other such conditions, deposition of aerosols becomes increasingly more central as the disease progresses (1,3). There is evidence to suggest that finer droplets (<3,~m) may penetrate more effectively to the lung peripheries in these patients. The standard method of generating fine aerosols, using jet nebulizers, has been to increase the effectiveness of the baffles within the system. However, the use of more effective baffles within the nebulizer itself substantially increases the time taken for a dose to be nebulized, while the use of an external baffle placed between the nebulizer and patient reduces the total dose of drug delivered. A new approach was sought in order to generate fine aerosols while maintaining the relatively high rates of drug delivery characteristic of conventional jet nebulizers. An auxiliary chamber (volume 1 1) was designed (Fig. 1) to be used with any conventional jet nebulizer. Adjacent to the nebulizer inlet is a one-way entrainment valve and an inlet for an auxiliary ‘drying’ air supply. As with the nebulizers driving gas flow (DGF), the ‘drying’ flow could be varied