Theoretical Lung Deposition of Hygroscopic NaCl Aerosols

Abstract

Hygroscopic aerosols grow in size as they are inhaled into the humid airways. An empirical formula describing the growth rate is derived from the results of an exact calculation. The approximate particle growth relation is used to calculate total and regional depositions of dry NaCl aerosols in the human respiratory tract for initial particle diameters ranging from 0.01 to 10 am. Assuming a relative humidity of 99.5% in the airways, total deposition results are found to be in good agreement with recent experimental data, and show a minimum deposition near 0.08 pm. For particles with an initial diameter larger than 0.2 pm, it is found that total deposition is increased due to particle hygroscopicity, whereas an opposite trend is seen for particles initially smaller than 0.2 pm. In most cases, deposition patterns vary appreciably due to the growth of the particles.

Pulmonary drug delivery. Part I: Physiological factors affecting therapeutic effectiveness of aerosolized medications

“…Ferron and colleagues [42, 43] have predicted that for initial sizes between 0.7 µm and 10 µm, total deposition of hygroscopic aerosols increases by a factor of 2. However, Xu and Yu [44] demonstrated that for NaCl particles with an initial size of 0.1 µm, the distribution pattern in the airways was similar to that for nonhygroscopic particles of the same size with diffusion remaining the primary mechanism of deposition. Using 2D‐imaging to detect deposition changes may be unsuccessful.…”

Physical Characterization of TRK-720 Hydrate, the Very Late Antigen-4 (VLA-4) Inhibitor, as a Solid Form for Inhalation: Preparation of the Hydrate by Solvent Exchange among Its Solvates and Mechanistical Considerations

“…Therefore, to develop a DPI formulation, an active pharmaceutical ingredient (API) crystallized from solution must be pulverized to control particle size. Three physical properties are necessary to achieve a stable medicinal effect as a DPI formulation: (1) the API should be physically and chemically stable on contact with the carrier (lactose), (2) in order to reach the lower airways, particles of the API should be 1–10 µm in diameter, and the API should be physically stable under pulverization (jet milling), and (3) when the API absorbs moisture in the mouth, the diameter and the density of its particles increase and it cannot reach the target area as a drug formulation,6 so it has to be low relative humidity. To satisfy these requirements, a crystal form is needed.…”

A Model of Deposition of Hygroscopic Particles in the Human Lung

“…Treatment of hygroscopic particle deposition in models of the respiratory tract is markedly different from that of insoluble particles, since hygroscopic particles may undergo continuous size change during travel in the lung; an increase in size directly influences the amount and site of deposition (Martonen 1982;Xu and Yu 1985;Persons et al 1987;Stapleton et al 1994). The approach to finding deposition of insoluble particles is rather straightforward.…”