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Respiratory deposition of inhaled micron particles in subjects with mild asthma
Citation:
KIM, C. S. AND H. Shu-Chieh. Respiratory deposition of inhaled micron particles in subjects with mild asthma. Presented at American Thoracic Society Annual Meeting, San Diego, CA, May 15 - 20, 2009.
Impact/Purpose:
research results
Description:
Rational: Particulate matter (PM) in the ambient air can cause adverse health effects to some people including an aggravation of asthma. Although compromised lung conditions in disease are likely to be the primary cause of the effects, enhanced respiratory dose of particles may also play an important role in causing the adverse health effects in patients with obstructive airway disease. Methods: We measured total (TDF) as well as regional deposition fraction (RDF) values in mild asthmatic subjects (n=16) for monodisperse micron size aerosols (Dp = 1, 3 and 5 micron diameter) at a few typical breathing patterns and compared the results with those obtained from young normal adults (n=15). For TDF, the subjects inhaled aerosols from a large bag following prescribed breathing patterns displayed on the computer monitor and TDF was determined from total number of particles inhaled and subsequently exhaled for each breath. For RDF, the serial bolus aerosol inhalation method was used for targeted delivery of aerosols to specific lung regions and deposition values in 10 sequential volume compartments (50 ml interval) from the mouth were obtained. Results: Mean TDF in asthmatic subjects was 0.19 ±.05, 0.42 ±.06, 0.59 ±.05 for Dp = 1, 3, and 5 µm, respectively at tidal volume of 500 ml and breathing frequency of 15 breaths/min, and these values were slightly greater (3-18%) than those from normal subjects (p = NS). Trend, however, is somewhat variable depending on breathing patterns. TDF was consistently greater (10-20%) in female than male subjects for Dp = 3 and 5 um but not for Dp=1 um. RDF values of asthmatics were slightly greater at the peak, and peak deposition sites were shifted to the proximal regions resulting in an increase in tracheobronchial deposition for Dp = 3 and 5 um. Alveolar deposition was slightly reduced because of the proximal shifting. Conclusions: Total lung deposition of particles in mild asthmatic subjects is not much greater than those in normals, but local airway deposition is enhanced at the expense of alveolar deposition. This may cause somewhat elevated airway response to PM in subjects with mild asthma. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.