The major components of a SVN consists of gas inlet/orifice, baffles, housing containing the liquid medicine and a capillary tube.
Baffles
One key feature in the SVN design is the baffles. The baffling system decreases both the MMAD and the GSD of the generated aerosol by impacting the larger aerosol out of air stream.
MMAD (Mass Median Aerodynamic Diameter): the mass median of the distribution on an aerodynamic diameter basis.
GSD (Geometric Standard Deviation): the ratio of the diameter below which 84.1% of the particles lie to the median diameter.
Residual or dead volume
Residual or dead volumeis the liquid volume of medication that remains in the SVN after the device runs dry. The residual volume varies from as little as 0.5 mL to more than 2.2 mL. Depending on the design and operation, sometimes it can be more than two thirds of the total dose.
Capillary tube
The capillary tube is a hollow tube, immersed in the liquid, that surrounds the orifice. The small spacing between the capillary tube and the orifice allows the liquid to reach the top during operation. It is the critical component that ensures the supply of medicine to the gas inlet.
