Aerosol recovery from large-volume reservoir delivery systems is highly dependent on the static properties of the reservoir
In this study, the role of electrostatic fields on aerosol recovery from a system with a large collapsible reservoir (30 L) was investigated. In addition, the efficacy of the reservoir method for bronchial challenge procedures was assessed in vivo. Aerosol recovery was determined by measuring the fraction of aerosol (0.05% 99mTc-tagged human albumin solution) retrieved from the reservoir. Before aerosol recovery experiments, electrostatic fields in the reservoir were measured. Aerosol recovery varied significantly with wall thickness of the reservoir and presence of an antistatic coating (range 6.0-70.3%). A close inverse relationship was found between the mean electrostatic field in the reservoir and aerosol recovery. The nebulized provocative concentration of histamine causing a 20% fall in forced expiratory volume in one second in asthmatics was found to be approximately half that of a standard method when compared with the reservoir system (mean ratio 2.24 (95% confidence interval, 1.60-3.12)). Recovery from an aerosol delivery system with a relatively large collapsible aerosol reservoir was highly dependent on the electrostatic field in the reservoir. In these systems the use of electrostatic field dissipative material for the reservoir is therefore recommended.
The physical properties of a jet-nebulizer and their relevance for the histamine provocation test.
We have examined the physical properties of eight specimens of a frequently used jet-nebulizer (Wiesbadener Doppelinhalator). For each nebulizer, under various conditions we measured driving pressure, solution output, solute output, particle concentration and size distribution in the aerosol, and the change of solute concentration in the storage vessel. Using histamine acid phosphate solutions in distilled water, there was considerable variability between the nebulizers in solute output (range about a factor 3). Solute output was strongly related to driving pressure (r2 = 0.89), to solution output (r2 = 0.96) and to particle concentration (r2 = 0.87). The particle size distributions of the eight nebulizers were very similar. The volume median aerodynamic diameter (VMAD) of the stable evaporated particles was on average 0.33 micrograms (geometric standard deviation of 1.78), which implies a VMAD of the primary droplets of about 3.2 micrograms. In fifteen subjects with bronchial hyperreactivity, a twofold increase of histamine output of the nebulizer without a change in particle size resulted on average in a twofold decrease of the histamine concentration that caused a 20 per cent fall (PC20) in FEV1. At constant histamine output the administration of dry particles instead of direct nebulization of (partly) saturated droplets into the mouth increased PC20 by a factor 2. This difference could not be explained by a changed deposition in the hypopharynx. There were large interindividual differences in the response to the altered aerosol characteristics. We conclude that the physical properties of the administered aerosols should be carefully controlled since they influence the biological response to inhaled histamine. The solute output of the investigated jet-nebulizer can satisfactorily be validated by weighing, for which an equation is given. In bronchial provocation testing, administration of dry particles is recommended.
Die wisselwerking tussen ekonomiese en konstitusionele hervormings in Suid‐Afrika
Abstract This article deals with the interplay between economic and constitutional reforms in South Africa. Historical and contemporary forces which obtain in these spheres are taken into consideration after which a number of conclusions are drawn.