Scientific basis for aerosol therapy using nebulizers.

Important properties of nebulizers for aerosol particle therapy are the water and solute output, and the initial particle size distribution. These properties have to be determined experimentally. The evaporation of the particles during transport is estimated to be less than 10% in most cases. The changes in particle size during inhalation, and particle deposition, are estimated with a hygroscopic particle lung deposition model. The regional deposition of aerosol particles of an arbitrary material and an arbitrary size distribution can now be estimated. This method is applied to two jet nebulizers (Pari Inhalierboy and Wiesbadener Doppelinhalator), and to an ultrasonic nebulizer (DeVilbiss 65)

On the deposition of aerosols in the human airways

Applied Science

Influence of different humidity profiles on the deposition probability of soluble particles in the human lung.

Hygroscopic aerosol particles will grow during respiration depending on their own properties and the local relative humidity (RH). Lung deposition models are used to approximate the local deposition of NaCl aerosol particles for different humidity distributions in the upper human airways. A method has been described by G. A. Ferron et al. , which enables the determination of the local temperature, water vapor concentration and RH of the air in the nasopharynx and upper human airways. The mean RH over an airway cross-section shows a fast increase in the nasal region. It reaches a maximum value of 0. 997 in the trachea. A maximum in the particle size is found caused by the maximum in the RH. Such a maximum is not found for larger particle sizes. Since dry NaCl aerosol particles will not grow at RH less than approximately 0. 75, there is no growth in the nostrils. A delay in growth of 0. 01 sec is found. Three lung deposition models are used in the study reported, and one model is then reapplied to determine the local and total deposition probability of a single NaCl particle during the respiration circle. Refs

Physical and chemical analysis of cobalt oxide aerosol particles used for inhalation studies.

Recent studies have been conducted of the long term lung retention depending on some physicochemical parameters of cobalt oxide aerosols which had been inhaled by dogs. They are produced under controlled conditions including a high temperature process described earlier by W. G. Kreyling and G. A. Ferron. In this paper the physical and chemical properties of the cobalt oxide particles produced under various conditions are discussed. The aerosols are produced by thermal degradation of monodisperse cobalt nitrate aerosols at degradation temperatures between 800 degree C and 1200 degree C resulting in monodisperse cobalt oxide particles. All cobalt oxide particles generated at various temperatures consist of amorphous and polycrystaline structures of both cobaltous oxide CoO and cobaltosic oxide Co//3O//4. The density of the particles degraded from cobalt nitrate is about half of the bulk density resulting in porous particle bodies with an increased surface area. The density of the small sized particles condensed from vaporized CoCl//2 is about 15% of the bulk density

Production of cobalt oxide aerosols with a modified spinning-top aerosol generator.

This aerosol generation system enables the production of monodisperse metal oxide aerosols which can be labeled radioactively. The production method consists of the nebulization of a metal-salt solution into monodisperse droplets by a 'May spinning-top aerosol generator', predrying of the droplets, crystal water extraction out of the salt crystals, thermal degradation up to 1200 degree C into metal oxide particles and subsequent cooling to room temperature. Cobalt oxide aerosols with **5**7Co radioactive labeling have been produced and analyzed extensively. In order to study the influence of the angular air jet on the efficiency, measurements have been carried out in which the ratio of the mass of monodisperse droplets per unit time and liquid feed rate is calculated. The size of the droplets follows the equation of Walton and Prewett. In order to study the stability of the aerosol particles, a standardized long-term dissolution test has been developed