Aerosol clearance

Mogulkoc N, Brutsche MH, Bishop PW, Murby B, Greaves MS, Horrocks AW, Wilson M, McCullough C, Prescott M, Egan JJ Greater Manchester Pulmonary Fibrosis Consortium. Pulmonary (99m)Tc-DTPA aerosol clearance and survival in usual interstitial pneumonia (UIP). Thorax 2001 56(12) 916-23. 

Sanchis J, Dolovich M, Chalmers R, Newhouse M. Quantitation of regional aerosol clearance in the normal human lung. J Appl Physiol 1972 33(6) 757-762. 

The role of the tracheobronchial circulation in aerosol clearance has been discussed by Wagner (1995). Its supportive role for ciliated cells and mucus glands has not been studied. For this reason it is unclear whether this circulation plays a significant part in maintaining mucociliary clearance. Consequently, the capacity of the airway circulation to influence the clearance of soluble and insoluble particles remains ill-defined and requires investigation at a fundamental level. 

WMRI mice Inhaled Pb, 13-14 j,g/m Pb aerosol Clearance rate of S. marcescens versus Pb exposure Clearance of S. marcescens significantly reduced Schlipkoter and Frieler (1979)... 

Wagner EM. The role of the tracheobronchial circulation in aerosol clearance. J Aerosol Med 1995 8 1-5. 

TI8. Schlesinger, R. B. (1989). Factors affecting the response of lung clearance systems to acid aerosols role of exposure concentration. E.nviron. Health Perspect. 79, 121-126. 

Several groups investigated the use of liposomes for the intra-pulmonary delivery. Farr et al. (1985) showed that the deposition of aerosolized liposomes in the human lung depends on the aerosol particle size. Short-term retention profiles for MLVs and SUVs deposited in the lung were indicative of clearance via the mucociliary transport mechanism. 

The ICRP (1994b, 1995) developed a Human Respiratory Tract Model for Radiological Protection, which contains respiratory tract deposition and clearance compartmental models for inhalation exposure that may be applied to particulate aerosols of americium compounds. The ICRP (1986, 1989) has a biokinetic model for human oral exposure that applies to americium. The National Council on Radiation Protection and Measurement (NCRP) has also developed a respiratory tract model for inhaled radionuclides (NCRP 1997). At this time, the NCRP recommends the use of the ICRP model for calculating exposures for radiation workers and the general public. Readers interested in this topic are referred to NCRP Report No. 125 Deposition, Retention and Dosimetry of Inhaled Radioactive Substances (NCRP 1997). In the appendix to the report, NCRP provides the animal testing clearance data and equations fitting the data that supported the development of the human mode for americium. 

Davies CP, Hodgson A, Stradling GN, et al. 1992. Studies on the nasal clearance of 238Pu and 241 Am nitrates. J Aerosol Sci 23(Suppl. 1) S511-S514. 

The first purified and characterized drug substances were administered as aerosols as a topical treatment for asthma approximately 50 years ago. More recently, drugs have been evaluated for systemic delivery. For each category of drug the mechanism of clearance from the airways must be considered. These mechanisms may be listed as mucociliary transport, absorption, and cell-mediated translocation. The composition and residence time of the particle will influence the mechanism of clearance. 

Drug delivery to the respiratory tract has been characterized in the past decade by an increase in knowledge of drug droplet or particle manufacture, behavior, aerosol dispersion, lung deposition and clearance. The number of diseases for which aerosol therapy may be applicable has increased dramatically. The pharmaceutical scientist is no longer limited to pulmonary diseases as therapeutic targets. Substantial progress has been made in every area of pharmaceutical aerosol science, and it is anticipated that this will ultimately lead to many new therapies. 

AJ Hickey. Lung deposition and clearance of pharmaceutical aerosols What can be learned from inhalation toxicology and industrial hygiene Aerosol Sci Technol 18 290-304, 1993. 

Most dosimetry models have incorporated the so-called Weibel A airway dimensions (Weibel, 1963) in order to calculate aerosol deposition, clearance and the density of alpha-decays per unit surface... 

Figure 5. Doses averaged over all epithelial cells in the bronchial and alveolar regions of the lung per unit exposure to potential alpha-energy as a function of aerosol size, compared with doses to basal cells for several models of airway size and clearance behaviour.

Clearance to pulmonary lymph nodes will occur at a fractional rate of 0.0001 per day. Dissolution of the deposited particles and absorption of cerium into the systemic circulation will occur at rates that are between the extremes represented by CeCh in CsCl particles and Ce oxide or Ce in fused aluminosilicate particles as given by the functions included in Figure 9. These rates should not be expected to be constant over the entire clearance period and will depend upon the overall composition of the bulk aerosol particles, which indude particle size, amount of stable lanthanide present, acidity, and the solubility of other components of the particles. The accuracy of predicting respiratory tract clearance and internal organ uptake of radiocerium will depend heavily upon adequate determination of the particle solubility characteristics. 

Hofmann, W. and Sturm, R., Stochastic model of particle clearance in human bronchial airways, J. Aerosol. Med. 17, 1, 73, 2004. 

---