Thoracic fraction of inhaled fiber aerosol

A Pediatric Upper Airway Library to Evaluate Interpatient Variability of In Silico Aerosol Deposition

The airway of pediatric patients' changes through development, presenting a challenge in developing pediatric-specific aerosol therapeutics. Our work aims to quantify geometric variations and aerosol deposition patterns during upper airway development in subjects between 3.5 months-6.9 years old using a library of 24 pediatric models and 4 adult models. Computational fluid-particle dynamics was performed with varying particle size (0.1-10 μm) and flow rate (10-120 Lpm), which was rigorously analyzed to compare anatomical metrics (epiglottis angle (θE), glottis to cricoid ring ratio (GC-ratio), and pediatric to adult trachea ratio (H-ratio)), inhaler metrics (particle diameter, [Formula: see text], and flow rate, Q), and clinical metrics (age, sex, height, and weight) against aerosol deposition. Multivariate non-linear regression indicated that all metrics were all significantly influential on resultant deposition, with varying influence of individual parameters. Additionally, principal component analysis was employed, indicating that [Formula: see text], Q, GC-ratio, θE, and sex accounted for 90% of variability between subject-specific deposition. Notably, age was not statistically significant among pediatric subjects but was influential in comparing adult subjects. Inhaler design metrics were hugely influential, thus supporting the critical need for pediatric-specific inhalable approaches. This work not only improves accuracy in prescribing inhalable therapeutics and informing pediatric aerosol optimization, but also provides a framework for future aerosol studies to continue to strive toward optimized and personalized pediatric medicine.

Insulation fiber deposition in the airways of men and rats. A review of experimental and computational studies

The typical insulation rock, slag and glass wool fibers are high volume materials. Current exposure levels in industry (generally ≤ 1 fiber/cm³ with a median diameter ∼1 μm and length ≥10 μm) are not considered carcinogenic or causing other types of severe lung effects. However, epidemiological studies are not informative on effects in humans at fiber levels >1 fiber/cm³. Effects may be inferred from valid rat studies, conducted with rat respirable fibers (diameter ≤ 1.5 μm). Therefore, we estimate delivery and deposition in human and rat airways of the industrial fibers. The deposition fractions in humans head regions by nasal (∼0.20) and by mouth breathing (≤0.08) are lower than in rats (0.50). The delivered dose into the lungs per unit lung surface area during a 1-day exposure at a similar air concentration is estimated to be about two times higher in humans than in rats. The deposition fractions in human lungs by nasal (∼0.20) and by mouth breathing (∼0.40) are higher than in rats (∼0.04). The human lung deposition may be up to three times by nasal breathing and up to six times higher by oral breathing than in rats, qualifying assessment factor setting for deposition.