Extrathoracic region fractional deposition

Regional deposition fractions of a 1 p,m AMAD aerosol, their distributions and characteristics have been determined as functions of age, gender and breathing pattern (Table 27.2 and Harvey, 2003). All are shown to follow similar trends (Harvey, 2003 Harvey and Hamby, 2002 Harvey and Hamby, 2001). The frequency distributions of regional deposition fraction are described by a normal distribution for the BB and extrathoracic regions. The bb and AI regions are best described by a lognormal distribution. 

The extrathoracic deposition fraction estimates developed in this study do not compare well with the results from Stahlhofen et al. (1983), who observed no regional deposition of particulates in the extrathoracic region. Particles of these sizes, 1 and 2 pm aerodynamic diameters, are expected to be deposited in the extrathoracic regions therefore, the discrepancy is of limited concern. This trend is consistent for individuals, regardless of the breathing pattern and gender therefore, extrathoracic deposition estimates are contrasted with theoretical data (Harvey, 2003). 

The ICRP deposition model estimates the fraction of inhaled material initially retained in each compartment (see Figure 3-2). The model was developed with five compartments (1) the anterior nasal passages (ET,) (2) all other extrathoracic airways (ET2) (posterior nasal passages, the naso- and oropharynx, and the larynx) (3) the bronchi (BB) (4) the bronchioles (bb) and (5) the alveolar interstitium (AI). Particles deposited in each of the regions may be removed and redistributed either upward into the respiratory tree or to the lymphatic system and blood by different particle removal mechanisms. 

Extrathoracic deposition during mouth breathing (DEet-m) is derived from the collection efficiency weighted by the fraction of tidal volume (1 flowing through this region... 

CF is a correction factor applied for gender, is the dead space volume, composed of the extrathoracic and the tracheobronehiolar volumes. It is approximated to 147 and 118 cm for male and female adults (168). The deposited fraction in the alveolar region (DEa) is... 

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