Particle size lung deposition

The aim was to identify the influence of particle size on deposition in different regions of the lung. In contrast to the approach of investigators in the fields of environmental health and industrial hygiene, the inhalation aerosol formulator wants the particles or droplets to be small enough to deposit in the lung [8,9]. The particles or droplets should be in a size range that allows them, suspended in air, to pass beyond the first surfaces they encounter on inspiration, those of the mouth, throat, and upper airways, and to pass to the lower airways. 

Insoluble plutonium is inhaled as particles. Particle size determines deposition patterns and consequently, clearance patterns from the lung therefore, particle size is directly related to retention and the resulting radiological dose. These characteristics also affect the toxicity and target organs of the various isotopes. 

Scheuch, G., and Stahlhofen, W. (1992). Deposition and dispersion of aerosols in the airways of the human respiratory tract the effect of particle size. Exper. Lung Res. 18, 343-358. 

Several groups investigated the use of liposomes for the intra-pulmonary delivery. Farr et al. (1985) showed that the deposition of aerosolized liposomes in the human lung depends on the aerosol particle size. Short-term retention profiles for MLVs and SUVs deposited in the lung were indicative of clearance via the mucociliary transport mechanism. 

Lung deposition patterns and the relative contributions of the fecal and urinary pathways vary with the aerosol particle size. Evidence for this is provided by a study in which dogs inhaled Am02 aerosols having... 

For extrathoracic deposition of particles, the model uses measured airway diameters and experimental data, where deposition is related to particle size and airflow parameters, and scales deposition for women and children from adult male data. Similar to the extrathoracic region, experimental data served as the basis for lung (bronchi, bronchioles, and alveoli) aerosol transport and deposition. A theoretical model of gas transport and particle deposition was used to interpret data and to predict deposition for compartments and subpopulations other than adult males. Table 3-4 provides reference respiratory values for the general Caucasian population during various intensities of physical exertion. 

Most lung deposition models are based on the influence of particle size on aerosol deposition. Breathing parameters, such as breathing frequency and tidal volume, play a key role in lung deposition [15]. Table 2 shows the breathing parameters for healthy male volunteers subjected to various levels of exercise on a bicycle ergometer [16], There are known differences in these parameters based on gender, age, and disease... 

None of the pharmacopeias state any requirements for particle size. However, the particle size specifications set should be appropriate for the intended use of the product. For example, if the particles are intended to reach the deep lung, the MMAD of particles exiting the device should be less than 5 xm. In general, the smaller the aerosol MMAD, the greater the deposition in the lung. 

In contrast, a decreasing proportion of particles from 1 p (100%) up to lOp (1%) reaches the pulmonary region in the human lung during normal breathing via the nose. Once there, maximum pulmonary deposition occurs for particle sizes of l-4p about 25% of Ip, 35% of2p, 30% of 3p, and 25% of4p. °... 

The critical factor in the development of the syndrome is the size of the ultrafine zinc oxide particles produced when zinc is heated to temperatures approaching its boiling point in an oxidizing atmosphere." The particles must be small enough (zinc oxide powder is either inhaled or taken orally. Only freshly formed fume causes the illness, presumably because flocculation occurs in the air with formation of larger particles that are deposited in the upper respiratory tract and do not penetrate deeply into the lungs. ... 

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