Nebulizers fluids

Fig. 1 illustrates the two mechanisms proposed for the processes of liquid disintegration and aerosol generation within ultrasonic nebulizers. The capillary-wave theory relates to the production of capillary waves in the bulk liquid. These waves constructively interfere to form peaks and a central geyser. When the amplitude of the applied energy is sufficiently high, the crests of the capillary waves break off, and droplets are formed. The rate of generation of capillary waves is dependent on both the physicochemical properties of the nebulized fluid and the intensity of the ultrasonic vibration. Mercer used Eq. (1) to calculate the threshold amplitude for the generation of capillary waves ... 

Patient compliance with prescribed nebulization regimes is primarily determined by the duration of the therapy. Nebulizer fluids may be atomized for a set period, or more usually, a measured volume of therapeutic liquid is nebulized to dryness. The time taken to achieve this is directly related to the volume to be delivered. However, not all the fluid in the nebulizer can be atomized, and some fluid remains associated with the baffles, internal structures, and walls of the nebulizer as the dead or residual volume. The proportion of fluid remaining as the residual volume and thus unavailable to patients is higher for smaller fill volumes. 

The presence of low ion concentrations in the nebulizer fluid was desirable as it enhanced the aerosol generation and reduced the variability of droplet size and aerosol output. Increased ion concentration also resulted in a decrease in droplet size and a subsequent increase in the FPF, particularly for the Omron nebulizer. 

Figure 4.1.2 is a photograph of a coimterflow burner assembly. The experimental particle paths in this cold, nonreacting, counterflow stagnation flow can be visualized by the illumination of a laser sheet. The flow is seeded by submicron droplets of a silicone fluid (poly-dimethylsiloxane) with a viscosity of 50 centistokes and density of 970 kg/m, produced by a nebulizer. The well-defined stagnation-point flow is quite evident. A direct photograph of the coimterflow, premixed, twin flames established in this burner system is shown in Figure 4.1.3. It can be observed that despite the edge effects.

Droplet delivery from an airblast nebulizer is governed by the surface tension, density and viscosity of the fluid, and the applied pressure, which can be passive or forced. Droplet breakup is illustrated in Fig. 6. Droplets form during this breakup at a critical Weber number (We) ... 

It would be possible to write an entire book on the topic of emission spectrometry instrumentation devoted only to solution samples. There has been a literal mountain of research devoted to better thermal sources—gas flame, gas plasma and shrouded flames for often as a fluid sample in the form of an aerosol which is dried in the flame and the atoms in the salt are then excited. Clearly, the flow rate into a nebulizer that forms the aerosol must be constant, the droplet size consistent and more. 

The increase in velocity seen as part of the Venturi effect simply demonstrates that a given number of fluid particles have to move faster through a narrower section of tube in order to keep the total flow the same. This means an increase in velocity and, as predicted, a reduction in pressure. The resultant drop in pressure can be used to entrain gases or liquids, which allows for applications such as nebulizers and Venturi masks. 

There are many examples of relatively straightforward use of ICP-MS for the analysis of biological fluids. Antimony has been measured in blood after a 14 1 dilution [236]. Cesium serum levels were found to be elevated in patients with alcohol dementia but not in Alzheimer s disease patients [237]. Cobalt levels in rat serum depended on the form of cobalt [238] ingested. Bismuth levels were measured in human blood and urine by using a direct injection nebulizer [239]. Lead was measured in the blood and blood plasma of smelter workers and the general population [240]. The measurement of trace elements in serum by ICP-MS has been compared to results from neutron activation analysis and proton-induced x-ray emission [241]. Semiquantitative analysis can also be used to obtain a rapid screening of samples [242]. 

These direct ion sources exist under two types liquid-phase ion sources and solid-state ion sources. In liquid-phase ion sources the analyte is in solution. This solution is introduced, by nebulization, as droplets into the source where ions are produced at atmospheric pressure and focused into the mass spectrometer through some vacuum pumping stages. Electrospray, atmospheric pressure chemical ionization and atmospheric pressure photoionization sources correspond to this type. In solid-state ion sources, the analyte is in an involatile deposit. It is obtained by various preparation methods which frequently involve the introduction of a matrix that can be either a solid or a viscous fluid. This deposit is then irradiated by energetic particles or photons that desorb ions near the surface of the deposit. These ions can be extracted by an electric field and focused towards the analyser. Matrix-assisted laser desorption, secondary ion mass spectrometry, plasma desorption and field desorption sources all use this strategy to produce ions. Fast atom bombardment uses an involatile liquid matrix. 

Decontamination and Treatment Remove animal from affected areas. If any coughing or respiratory distress, monitor blood gases and Sp02- Provide oxygen and assisted ventilation as needed. Nebulized beta agonists and possibly corticosteroids can be used to treat bronchospasm. Monitor electrolytes and PCV as there can be fluid shifts out of the vasculature (Goldfrank et al, 2002). Urine arsenic levels may be measured, but are not clinically useful due to the lag time before results are obtained. Watch for liver and kidney failure. 

Emad, A., Emad, Y. (2007b). Relationship between airway reactivity induced by methacholine or ultrasonically nebulized distilled cold water and BAL fluid cellular constituents in patients with sulfur mustard gas-induced asthma. J. Aerosol Med. 20 342-51. 

Table 1 Average mass median diameter for fluids nebulized in a Pari LC nebulizer...

McCallion, Orla, N.M. Taylor, Kevin, M.G. Thomas, Marian Taylor, Anthony J. Nebulization of fluids of different physicochemical properties with air-jet and ultrasonic nebulizers. Pharm. Res. 1995, 12 (11), 1682-1688. 

The Bespak Piezo Electric Actuator is a novel aerosol delivery system based on a piezoelectric crystal combined with an electroformed mesh (Fig. 3). It produces droplets of adjustable size from a single metered drop or fluid reservoir. The mesh hole dimension (as small as 3 pm) determines the size of the droplets produced, whereas the size and density of the holes control the rate of fluid delivery. These can be varied according to the formulation. Although solutions are more readily nebulized, suspensions can be aerosolized if the particle size of the suspended particles is two to three times smaller than the mesh size. 

Warming may have a beneficial effect. For instance, the temperature of fluids atomized in air-jet nebulizers decreases by approximately 10-15°C during use, resulting in bronchoconstriction in some asthma suffers.Bronchoconstriction, which is most marked at 5°C, disappears at 37°C and thus may be minimized by using an ultrasonic device. Furthermore, when solutions of drugs with low solubility are to be nebulized, ultrasonic nebulizers, which warm the solutions, may be preferable to air-jet devices, which cool them and may cause precipitation. However, the heat generated may harm heat-labile materials such as diethylenetriaminepentoacetic acid ( mTc-/DTPA), " proteins, and some antibiotic solutions. Thus, ultrasonic nebulizers are specifically prohibited for aero-solization of recombinant human deoxyribonuclease (rhDNase). ... 

When coupling a low-pressure detector such as the ELSD with SFC, detection takes place at atmospheric pressure, usually downstream of the back-pressure regulator [2]. Figure la shows a common SFC-ELSD interface with downstream pressure control. Factors affecting ELSD response in this configuration include nebulizer design, evaporation conditions, carrier gas flow rate, and the use of makeup fluid. 

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