Spacer large volume

The single most important factor determining drug delivery is the size of the spacer large-volume spacers deUver more drug than small-volume spacers. The optimal size depends on the pMDI, and therefore dedicated spacers should... 

Oral candidiasis is seen in some 5-10% of patients who use inhaled glucocorticoids, particularly when oral hygiene is poor, but is rarely symptomatic. The risk can be reduced by the use of a large-volume spacer (141,142). 

Silvasti, M. Comparison of the beclomethasone dipropionate delivery by easyhaler dry powder inhaler and pMDI plus large volume spacer. J. Aerosol Med. 2001,... 

Figure 2a shows the separation of DNP-amino acids using three spacer acids (i.e., acetic acid, propionic acid, and n-butyric acid) in the stationary phase [2]. Hydrophilic DNP-glutamic acid is eluted between acetic and propionic acids DNP-alanine between propionic and n-butyric acids, and hydrophobic DNP-leucine after n-hu-tyric acid. The method can be effectively applied for the separation and concentration of a small amount of organic ions present in a large volume of the sample solution. However, the most useful application has been... 

If batteries are to be operated at elevated temperatures for extended periods, the relative density of the electrolyte should be decreased appropriately (generally to between 1.260 and 1.240). For low-temperature applications, batteries should have a large volume of electrolyte of high relative density to minimize the likelihood of freezing, and compressible separators and/or spacers that can absorb expansion should freezing and related expansion occur. The gel battery is considered to be the most appropriate VRLA technology for this task, as it can be constructed with an excess of acid. It also uses microporous separators, which should reduce the likelihood of short-circuits if the electrolyte were to freeze and expand. 

For pMDIs, in vitro studies do not take hygroscopic growth in the airways or the differences in plume geometry into account. The ability of the cascade im-pactor to predict the behavior of aerosolized drugs in vivo in a reliable way has been recently questioned. Indeed, it has been demonstrated that several generic pMDIs with fine particle fractions comparable to the original formulation (as measured in vitro) appeared to behave differently in vitro once attached to a large-volume spacer (3-5). 

Kenyon CJ, Dewsbury NJ, Newman SP. Differences in aerodynamic particle size distributions of innovator and generic beclomethasone dipropionate aerosols used with and without a large-volume spacer. Thorax 1995 50 846-850. 

Two decades later, various designs—including large-volume spacers. 

The aerosol cloud should be available over a prolonged period to minimize still further the need for coordination between actuation and inhalation. This is particularly important in young children with poor compliance, and shallow and irregular breathing patterns (Fig. 1). If inspiratory flow and tidal volume are low, several breaths may be required to obtain the whole volume of aerosol retained in the spacer. These factors may also be important in older children and adults with faulty coordination between inhalation and actuation, in whom emptying of a large volume spacer may be delayed. 

Sedimentation of drug particles in the aerosol is another factor that reduces the available aerosol and shortens the time available for inhalation after actuation. The velocity of sedimentation is proportional to the aerodynamic diameter of the particles. In a narrow spacer, the sedimentation distance is short and therefore the loss of aerosol is faster in small-volume tube spacers than in large-volume spacers. This principle is taken to its extreme in a vertical spacer, compared with the traditional horizontal spacer. 

In adults, the lung dose achieved with intermediate- and large-volume spacers is about twice that obtained with the corresponding pMDI alone (i.e., 20-35% of the metered dose) (28,61,90-92). In one study, lung doses from pMDIs with and without a large-volume spacer were similar (93), which may be explained by a lack of priming of the plastic spacer. The small-volume spacer AeroChamber de-... 

Keeley D. Large volume plastic spacers in asthma (commentary). Br Med J 1992 305 598-599. 

Lipworth BJ, Clark DJ. Early lung absorption profile of non-CFC salbutamol via small and large volume spacer devices. Br J Clin Pharmacol 1998 46 45-48. 

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