Background: Little is known about the effects of postnatal developmental changes in lung architecture and breathing patterns on intrapulmonary particle deposition. We measured deposition in the developing WKY rat, whose lung development largely parallels that of humans. Methods: Deposition of 2-μm sebacate particles was determined in anaesthetized, intubated, spontaneously breathing rats on postnatal days (P) 7 to 90 by aerosol photometry (Karrasch et al. 2009). Respiratory parameters were determined by body plethysmography. Results: Tidal volume increased substantially from P7 (0.19 mL) to P90 (2.1 mL) while respiratory rate declined from 182 to 113/min. Breath specific deposition was lowest (9%) at P7 and P90 and markedly higher at P35 (almost 16%). Structural changes of the alveolar region include a 9-fold increase in surface area (5). Particle deposition per unit of time and surface area (DST) peaked at P35 and showed a minimum at P90. At an inhaled particle number concentration of 10E5/cm3 an estimated 450, 690 and 290 particles/(min x cm2) at P7, P35 and P90, respectively. Multiple regression models showed that deposition depends on the mean linear intercept as structural component and the breathing parameters, tidal volume and respiratory rate (r2 >0.9). Discussion: Micron-sized particle deposition was dependent on the stage of postnatal lung development. A maximum was observed during late alveolarisation (P35), which corresponds to human lungs of about 8 years of age. Children at this age may therefore be more susceptible to micron-sized airborne environmental health hazards.
- aerosol photometry
- deposition model
- lung development
- Copyright © 2011, Journal of Applied Physiology