AERODYNAMIC DIAMETER OF NONSPHERICAL PARTICLES IN HUMAN AIRWAY : DEPOSITION OF DRY-POWDER INHALER

• Published in: JIBI INKOKA TEMBO Vol. 47; no. Supplement1; pp. 14 - 19
• Main Authors: Takano, Hiroshi, Kojima, Sayaka, Itoh, Masayuki, Hyo, Noboru, Majima, Yuichi
• Format: Journal Article
• Language: Japanese
• Published: Society of Oto-rhino-laryngology Tokyo 15.08.2004
• Subjects: aerodynamic diameter; dry powder inhaler; human airway model; local deposition fraction of drug; nonspherical drug particle
• ISSN: 0386-9687; 1883-6429
• DOI: 10.11453/orltokyo1958.47.Supplement1_14

Drug inhalation is regarded as the main therapy in the superior local deposition effect on the basis of drug delivery system (DDS). The local deposition fraction of drug particles is determined from an aerodynamic diameter as functions of particle size, shape, density, configuration, and orientation angle. Theoretical and experimental clarifications of the aerodynamic diameter for nonspherical drug particles are required to predict the amount of particles. A rotational ellipsoid approximation for nonspherical particles is applied to numerically determine the three-dimensional value of aerodynamic diameter. To evaluate local deposition of nonspherical drug particles in the human airway, the aerodynamic diameter is obtained experimentally from the equilibrium orientation angle and aspect ratio of nonspherical drug particles. The orientation angle of nonspherical particles in air fluid was calculated numerically. The two-dimension configuration, orientation, and velocity of nonspherical particles were measured in fluid by optical microscopy and a high-speed camera to obtain the aerodynamic diameter of particles. The aerodynamic diameter of particles was also measured directly by time-of-flight (TOF), and was compared with experimental results for measuring validity by optical microscopy. At a constant flow rate, the orientation angle was mainly on 0 degree and more homogeneous and the aerodynamic diameter measured by experiments agrees approximately with the date measured by TOF. We confirmed that more particles are aligned at 10-30 degrees decline with the flow direction in the shear flow. The aerodynamic diameter affected by orientation angle measured in the shear flow was slightly smaller than that measured by TOF. These results indicate that the experimental method is useful for measuring the aerodynamic diameter of particles in an arbitrary fluid. More effective treatment is expected from evaluating the physical quality of pharmaceuticals such as the alteration of the aerodynamic size distribution as functions of velocity gradient, density, and configuration of particles.