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:: Section 5
How does it work?A typical SVN is powered by a high-pressure stream of gas directed through a restricted orifice (the jet). The gas stream leaving the jet passes by the opening of a capillary tube immersed in solution. Because it produces low lateral pressure at the outlet, the high jet velocity draws the liquid up the capillary tube and into the gas stream, where it is sheared into filaments of liquid that break up into droplets. The primary spray produces a polydisperse aerosol with droplets in the 0.1- to 500 µm range. The primary spray is directed against one or more baffles. A baffle is simply a surface on which large particles impact and fall back to suspension, a process that decreases the MMAD and GSD of the output aerosol. A sphere or plate placed in line with the jet flow can serve as a baffle, as can the internal walls of the nebulizer, or the internal walls of the delivery system. In many designs, droplets that impact baffles in the SVN return to the medication reservoir to be nebulized again. The outlet of aerosols can be on the top or side of the SVN. The outlet should connect to mouthpiece and patient can use it directly.
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