Abstract
ABSTRACT Inhalation is the most important route of entry for aerosol particles. Deposition in the respiratory tract is affected by many factors, such as particle size, shape, charge, density, breathing pattern and physical tract structure. However, most of the currently available lung deposition data are on Caucasians, with very limited data on Taiwanese. Therefore, it is essential to clarify whether there is a significant difference in respiratory tract deposition between Caucasian and Taiwanese individuals. This work is thus aimed at characterizing regional lung deposition in Taiwanese. A rapid method of measuring regional lung deposition was employed in the present study. The experimental system consisted of an aerosol chamber, a mouthpiece, a pneumotachograph flow meter, and a particle counter. A cylinder-piston type breathing machine was used to generate a series of “standard” breathing patterns for subjects to follow. In addition to oral breathing, nasal breathing was also conducted. A special respirator was employed to facilitate measurements of the nasal route deposition. The regional lung deposition data obtained in this work showed good agreement with previous studies based on the bolus technique, indicating that the difference in lung deposition between Taiwanese and Caucasian individuals is negligible. The local deposition efficiency increased with the penetration volume. This increased trend was particularly prominent in the deep lungs, which was likely due to the dilution effect caused by the relatively clean air in the functional residual capacity. When a fixed fraction of the forced vital capacity was used to replace the fixed tidal volume, the total lung deposition became less dependent on the tidal volume. Primarily due to nostril hairs and the complex configuration of the nasal turbinate, the local deposition efficiency of the nasal route was higher than that of the oral route but only in the early stage of penetration (200 mL).
Highlights
Inhalation is the most important route for aerosol particles in the atmosphere to enter the body
The difference in local deposition efficiency increased sharply when entering the deep penetration volume (400– 500 mL). This mismatch with Kim’s data was likely due to (1) the two experimental systems not being exactly the same: The bolus technique was used in Kim’s study, while the rapid measurement system was employed in the present study; and (2) the breathing patterns differed: Constant velocity was adopted in Kim’s study, while the sinusoidal pattern was used in this work
The regional lung deposition data obtained using the newly developed rapid measurement system displayed good agreement with previous studies based on the bolus technique
Summary
Inhalation is the most important route for aerosol particles in the atmosphere to enter the body. The index of lung function measurement and the biological response caused by these inhaled particles vary with their site of deposition in the respiratory tract and the physiological or toxic effects within the target tissue. The health effect can be acute or chronic. It depends on the particle composition, size, and the region of lung, so it is necessary to determine the total. Various methods have been applied to measure regional lung deposition. Regional lung deposition has been measured by inhalation of particles labeled with γ-emitting radionuclide (Lippmann and Albert, 1969; Stahlhofen et al, 1980; Hashish et al, 1998; Möller et al, 2006; Rissler et al, 2017).
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