Deposition of spherical and fiber aerosols in human oral and upper tracheobronchial airways.
Cheng-YS; Su-WC; Zhou-Y
Proceedings of the AAAR 23rd Annual Conference, October 4-8, 2004, Atlanta, Georgia. Mount Laurel, NJ: American Association for Aerosol Research, 2004 Oct; :13
Inhalation exposure of spherical ambient and occupational aerosols may have serious health consequences including lung cancers and other respiratory diseases. The deposition pattern in the respiratory tract as a function of particle size is the information critical to understanding respiratory dosimetry and defining the index of exposure for health protection purposes. Physical replicas of human respiratory tract have been used to study the microdosimetry of inhaled particles. Increasingly, mathematical deposition models have been used to assess the dosimetry of inhaled fiber aerosol. However, current lung dosimetric models for fibers in the human respiratory tract are based on theoretical equations, which have not been verified with experimental data. The purpose of this study is to investigate the effects of aerosol size and breathing rate on the deposition pattern in a realistic human airway cast with a defined geometry for spherical and fiber aerosol. We also compared the experimental results to theoretical equations. The human airway cast used in this study included the oral cavity, pharynx, larynx, trachea, and three generations of bronchi. The oral portion of the cast was molded from a dental impression of the oral cavity in a human volunteer, while the other airway portions of the cast were made from a cadaver. Spherical PSL particles and carbon fibers diameter (3.74 mm) were used for the deposition study. The aerosol was generated with a small-scale powder disperser (Model 3433, TSI Inc., St Paul, MN). Regional fiber deposition was measured at a constant inspiratory flow rate of 15 to 60 L min-1. Deposition in each segment of oral and TB tree is measured by cutting the cast into sections corresponding to each region. The deposition efficiency in the oral region was found to be a unique function of the Stokes number, which combined the inertial particle size and flow rate for both spherical and fiber aerosol. In the tracheobronchial region, deposition in the first four generations were similar for both spherical and fiber aerosol as a function of Stokes number, which is reasonable as in the size range the impaction is the dominant deposition mechanism. The experimental data also in reasonable agreement with deposition theory of Cai and Yu (1988). Therefore, the airway replica consisting of oral, laryngeal, and tracheobronchial airways can be used to investigate deposition patterns and dosimetry of inhaled particles in air pollutants, occupational hazards, or pharmaceutical applications.
Aerosols; Inhalation-studies; Occupational-health; Occupational-exposure; Lung-cancer; Respiratory-system-disorders; Pulmonary-system-disorders; Dosimetry; Mathematical-models; Aerosol-particles; Models; Airway-obstruction; Airway-resistance; Occupational-hazards; Health-hazards
Proceedings of the AAAR 23rd Annual Conference, October 4-8, 2004, Atlanta, Georgia
Lovelace Biomedical & Environmental Research