The distribution of deposited dust between the alveolar and tracheobronchial regions of the lung has been measured for 2 µm (12 subjects) and 5 µm (50 subjects) unit relative density particle diameters by the radioisotope tracer technique. For the 2 and 5 µm particles 31 ± 6.6% and 54 ± 1.9% of the initial lung burden were deposited in the tracheobronchial region: the mean difference was highly significant (P < 0.001). Standardization of these and other published values for particle size and density, tidal volume and flow rate of inhalation and interval between inhalation and assessment of retention resulted in a considerable reduction in the scatter. The regression of the square of aerodynamic particle diameter (pd2 on percentage tracheobronchial deposition (%TB) after standardization was %TB = 20.7 + 0.6 pd2.
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Pavia et al. (1976) studied this question.