Halolite nebulizer

HaloLite, shown in Fig. 11, is a hand-held drug delivery system developed by Medic-Aid (Bognor Regis, United Kingdom). The device, which uses compressed air, consists of a medication chamber, a control unit, and an aerosol generation assembly that is operated by a portable, dedicated compressor. The aerosol is generated based upon conventional nebulization principles. The control unit allows the patient to select a... 

New adaptations of existing jet nebulizer technology to produce dosimetric systems for conventional generic nebulized drug delivery— e.g., Halolite and Circulaire... 

A. Traditional Nebulizer Technology Modified for Improved Generic Use (Halolite, Circulaire)... 

The Circulaire nebulizer system increases the rate and total aerosol dose delivered to the patient compared to the traditional constant-output nebulizer alone, and this has savings in treatment time as well as potentially reducing costs (12). Further, aerosol wasted to the environment is minimized, which, in turn, minimizes occupational exposures to drug aerosol (13,14). As with the Halolite system, the Circulaire is cumbersome and complicated to clean. 

The reservoir incorporated within the Circulaire nebulizer system may help increase the inhaled proportion of aerosol from a given fill volume compared to the same driving nebulizer without incorporation of the valved reservoir bag system. Like the Halolite, this implies reconsideration of prescribed doses and volume fills of drug solution to avoid overdosing. The extent to which the droplet size from conventional nebulizers is affected by adaptations in Halolite and Circulaire nebulizer system is not clear. Meaning in vitro measurements (e.g., European standard) characterizing droplet size from either system is not available. 

The small amounts of aerosol generated by a system such as Halolite are produced over relatively short time period (< 1 s) in a discrete bolus. This bolus is entrained with ambient air during patient inhalation and one would expect a considerable amount of mixing to occur. As ambient air has a significant capacity to absorb water vapor from nebulized aerosol (relative humidity normally <70%), evaporation of aqueous aerosol would be inevitable and rapid. The reduction in droplet size would be expected to be inconsistent, as the rate of evaporation will depend on the speed of inhalation which defines degree of dilution as well as temperature and humidity of ambient air. In contrast, aerosol-laden air inhaled from the Circulaire nebulizer system will entrain little ambient air and is therefore relatively less sensitive to any reduction in droplet size due to evaporation. To what extent evaporation reduces droplet size from Halolite is not known and deserves further investigation. 

The characteristics of both Respimat and AERx clearly differentiate them from traditional nebulizers and those traditional nebulizer systems that have been modified to increase output (Circulaire) or deliver discrete doses (Halolite). Both are being developed and marketed in conjunction with specific drugs that subsequently undergo clinical trials. Both are dosimetric in operation, are reported to have very low residual volumes, have low or no electrical power requirements, and both Respimat and AERx are thought to have good dose reproducibility. 

The European Standard presents a set of in vitro methods that are expected to reflect in vivo deposition and have been shown to provide repeatable and consistent results. It is clear that some nebulizer designs cannot easily be adapted into this or any other standard and that some flexibility is required in interpreting and applying such to these systems. In particular, obtaining a realistic profile of aerosol size distribution from the small aerosol boluses mixed with entrained ambient air from the Halolite, Circulaire, and AERx is particularly problanatic. However, such technical difficulties can be overcome and realistic measures of... 

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