Aerosols devices

Aerosol devices can be difficult to use for example, it has been estimated that approximately 50% or more adult patients have difficulty using conventional metered-dose inhalers efficiently, even after careful training. Dexterity is also required, which may be lacking in the very young and elderly populations. 

As you learned earlier, chlorolluorocarbons (CFCs) are chemicals that interfere with the ozone cycle high up in the atmosphere. CFCs are nontoxic, nonflammable compounds that contain atoms of chlorine, carbon, and fluorine. These gases are human-made compounds that were released into the atmosphere primarily from refrigeration and aerosol devices. 

An alternative dry powder aerosol device is illustrated in Fig. 9.46 and the mechanism of dispersion of powdered dmg in a Ventodisk or Becodisk system is shown in Fig. 9.47... 

Advances in the equipment for the administration of aerosol medication to horses have facilitated the widespread use of inhalation therapy in equine medicine. Newer aerosolization devices ease administration and make pulmonary drug delivery efficient. Aerosol therapy is likely to become the mainstay of treatment for horses with heaves and may prove beneficial in the treatment of infectious respiratory disease in horses. 

For MDIs, lung deposition can be enhanced by (1) gentle exhalation to residual volume rather than to functional residual capacity, (2) slow inhalation (lOL/min) rather that fast inhalation (50L/min), and (3) breath hold of 10 sec rather than none at end of puff inhalation. These observations were based on measurement of urinary albuterol at 30-min postinhalation, which is considered to reflect lung delivery and to avoid gastrointestinal (GI) tract deposition [36], The effect of inhalation flowrate through an aerosol device can greatly affect particle size, a factor that may explain in part the reduced deposition with suboptimal flowrates. Failure to quickly achieve optimal inspiratory flowrate via a budesonide Turbuhaler can result in an increase in size from <6.6 microns to... 

Jet nebulization (Figure 4.1-7), the cheapest and most common aerosol device in the pulmonary delivery arena, uses driving gas to accelerate liquid from a reservoir and achieve primary atomization. These primary droplets then hit an obstruction that causes splashing and spreading, which generates secondary droplets in the 1- to 10-pm range. 

Lentz Y, Anchordoquy T J, Lengsfeld C S (2006). Impact of Aerosolization Devices on plasmid DNA. J. Aerosol Med. In Press. 

Bisgaard H. Towards improved aerosol devices for the young child. Pediatr Pul-monol 1999 18 78. 

Certain types of equipment are specifically excluded from the scope of the directive. It is self-evident that equipment which is already regulated at Union level with respect to the pressure risk by other directives had to be excluded. That is the case with simple pressure vessels, transportable pressure equipment, aerosols and motor vehicles. Other equipment, such as carbonated drink containers or radiators and piping for hot water systems are excluded from the scope because of the limited risk involved. Also excluded are products which are subject to a minor pressure risk which are covered by the directives on machinery, lifts, low voltage, medical devices, gas appliances and on explosive atmospheres. A further and last group of exclusions refers to equipment which presents a significant pressure risk, but for which neither the free circulation aspect nor the safety aspect necessitated their inclusion. 

Solid samples can be analyzed using a plasma torch by first ablating the solid to form an aerosol, which is swept into the plasma flame. The major ablation devices are lasers, arcs and sparks, electrothermal heating, and direct insertion into the flame. 

The term nebulizer is used generally as a description for any spraying device, such as the hair spray mentioned above. It is normally applied to any means of forming an aerosol spray in which a volume of liquid is broken into a mist of vapor and small droplets and possibly even solid matter. There is a variety of nebulizer designs for transporting a solution of analyte in droplet form to a plasma torch in ICP/MS and to the inlet/ionization sources used in electrospray and mass spectrometry (ES/MS) and atmospheric-pressure chemical ionization and mass spectrometry (APCI/MS). 

Finally, in yet another variant, the sample liquid stream and the gas flow are brought together at a shaped nozzle into which the liquid flows (parallel-path nebulizer). Again, the intersection of liquid film and gas flow leads to the formation of an aerosol. Obstruction of the sample flow by formation of deposits is not a problem, and the devices are easily constructed from plastics, making them robust and cheap. 

Nebulizers are used to introduce analyte solutions as an aerosol spray into a mass spectrometer. For use with plasma torches, it is necessary to produce a fine spray and to remove as much solvent as possible before the aerosol reaches the flame of the torch. Various designs of nebulizer are available, but most work on the principle of interacting gas and liquid streams or the use of ultrasonic devices to cause droplet formation. For nebulization applications in thermospray, APCI, and electrospray, see Chapters 8 and 11. 

Nebulizers convert bulk liquid into an aerosol, consisting of a mix of small droplets of various sizes and solvent vapor. Such devices are used to transfer analyte solutions into the flame of a plasma torch. 

Sihcone contamination has been impHcated as a cause of failure in telephone switching systems and other devices that contain relay switch contacts (507). Analysis of airborne particulates near telephone switching stations showed the presence of siUcones at these locations. Where the indoor use of sihcones is intentionally minimised, outdoor levels were found to be higher than inside concentrations (508). Samples of particulates taken at two New Jersey office buildings revealed sihcone levels that were considerably higher indoors than outdoors. In these cases, indoor sihcone aerosols are beheved to be generated primarily by photocopiers, which use sihcone fuser oils. 

The AeroSizer, manufactured by Amherst Process Instmments Inc. (Hadley, Massachusetts), is equipped with a special device called the AeroDisperser for ensuring efficient dispersal of the powders to be inspected. The disperser and the measurement instmment are shown schematically in Figure 13. The aerosol particles to be characterized are sucked into the inspection zone which operates at a partial vacuum. As the air leaves the nozzle at near sonic velocities, the particles in the stream are accelerated across an inspection zone where they cross two laser beams. The time of flight between the two laser beams is used to deduce the size of the particles. The instmment is caUbrated with latex particles of known size. A stream of clean air confines the aerosol stream to the measurement zone. This technique is known as hydrodynamic focusing. A computer correlation estabUshes which peak in the second laser inspection matches the initiation of action from the first laser beam. The equipment can measure particles at a rate of 10,000/s. The output from the AeroSizer can either be displayed as a number count or a volume percentage count. 

Specific advancements ia the chemical synthesis of coUoidal materials are noteworthy. Many types of genera ting devices have been used to produce coUoidal Hquid aerosols (qv) and emulsions (qv) (39—43) among them are atomizers and nebulizers of various designs (30,44—50). A unique feature of produciag Hquid or soHd coUoids via aerosol processes (Table 3) is that material with a relatively narrow size distribution can be routinely prepared. These monosized coUoids are often produced by relying on an electrostatic classifier to select desired particle sizes ia the final stage of aerosol production. 

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