Deposition of Inhaled Ultrafine Aerosols in Replicas of Nasal Airways of Infants

Abstract

Experimentally measured deposition of ultrafine particles, ranging from 13-100 nm in diameter, in nasal airway replicas of ten infants aged 3-18 months is presented. The replicas included the face, nostrils, and nasal airways including the upper trachea. A differential mobility analyzer (DMA) and a condensation particle counter (CPC) were used to quantify the nasal deposition by comparing the number of polydisperse sodium chloride particles, generated by evaporation from a Collison atomizer, at the inlet and outlet of the replicas. Particles were individually classified in size by DMA and subsequently were counted one size bin at a time by CPC upstream and downstream of each replica. Since in vivo data is not available for infants to compare to, we validated our experimental procedure instead by comparing deposition in nasal airway replicas of six adults with in vivo measurements reported in literature. In the infant replicas, tidal inhalation was simulated at two physiologically compatible flow rates and the effect of flow rate on deposition was found to be small. Deposition obtained at constant flow rates is lower than with tidal breathing, indicating the importance of unsteadiness, in contrast to similar data in adults where unsteadiness is known to be unimportant. An empirical equation, containing geometrical features of the nasal airways in the form of related non-dimensional dynamical parameters (Reynolds, Schmidt, and Womersley numbers), was best fitted to the infant data. This equation may be useful for a priori prediction of nasal deposition and intersubject variability during exposure of infants to ultrafine aerosols.

Source and trajectories of inhaled particles from a surrounding environment and its deposition in the respiratory airway

“…A similar work to use such a high-resolution mesh is that of Doorly et al (2008). Earlier studies by the authors found that a mesh in excess of 2.0 million cells provided grid independence for the nasal cavity region (Inthavong et al, 2011a) among other studies (Golshahi et al, 2010;Lee et al, 2010;Moghadas et al, 2011), while a mesh of 1.2 million cells was sufficient for grid independence of the room with human occupant model (King Se et al, 2010). The visualization and generation of the mesh was possible on a PC computer with 32 Gb Ram, and 8 processor cores.…”

In vitro deposition measurement of inhaled micrometer-sized particles in extrathoracic airways of children and adolescents during nose breathing

“…We started our experimental procedure by choosing five replicas of adults (three males and two females) including the face (from chin to forehead including both cheeks), nostrils, and nasal airways to the level of upper trachea of those individuals who were used by us in recent work on deposition of nanoparticles in nasal airways of infants (Golshahi et al, 2010). In brief, MRI images of ten adults were obtained under the approval of the University of Alberta Health Research Ethics Board and the regions of interest were identified in those images based on grayscale level using the Mimics software package (Materialise, Ann Arbor, MI).…”

Aerosol Deposition in a Nasopharyngolaryngeal Replica of a 5-Year-Old Child

“…Nasal replicas have recently been developed in infants and children from 3 months to 14 years on the basis of computer tomographic scans at the University of Alberta (Storey-Bishoff et al 2008;Golshahi et al 2010Golshahi et al , 2011. The replicas were made of acrylic plastic.…”