Biomedical Engineering Reference
In-Depth Information
is a circular, wafer-thin metal plate with micrometer-size tapered holes (Figure
13) (Stangl et al., 2000; Ledermüller et al., 2003). The piezoelectric actuator is
driven by an electronic circuit in order to vibrate the membrane against the
medication fluid. Small jets of fluid are formed and passed through a
perforated plate in order to form droplets of controlled size and low velocity
(Dhand, 2002). The nebulized droplets of a steroid suspension were smaller
and more uniform using the eFlow nebulizer compared to droplets generated
from the Pari LC Plus/ Proneb Turbo air-jet system (Jauernig et al., 2003). The
eFlow nebulizer has also shown capable of delivering colloidal systems such
as liposomes (Wagner et al., 2006).
(Source: Ledermüller et al., 2003 ).
Figure 13. Design of the Pari e-Flow vibrating-mesh nebulizer. A piezoelectric
actuator driven by an electronic circuit causes vibrations in a plate containing tapered
holes to extrude the fluid and generate aerosol droplets.
3.4. Soft Mist Inhalers (SMIs)
Soft mist inhalers (SMIs) are propellant-free devices which produce slow
moving aerosols from drug solutions over an extended period of time (Hindle,
2004). An example of SMIs is the Respimat
®
inhaler (Boeringer Ingelheim,
Germany). In the Respimat
®
, the drug solution is stored in a collapsible bag
within a sealed plastic container surrounded by a cartridge. The manual
compression of a tension spring results in suction of the medication fluid
through a capillary tube. A metered dose of the fluid is forced through a
uniblock that produces two fine jets of liquid which collide in a controlled
angle to produce a spray of tiny droplets (Dalby et al., 2004). The Aerosol
generated from Respimat is long-lasting and slow-moving compared to
