Nasal deposition in infants and children.

Background: The variability of particle deposition in infant and child nasal airways is significant due to the airway geometry and breathing rate. Estimation of particle deposition in the nasal airway of this age group is necessary, especially for inhalation drug delivery application. Previous studies on nasal aerosol deposition were focused mostly on adult. A few empirical equations were also developed to calculate nasal deposition in different age groups of children. However, those studies have their limitations. The aim of this study is to find a simple way to calculate the nasal aerosol deposition in all age groups.

Methods: An in vitro test of micrometer particle deposition in nasal airways for three different ages of infants and children is conducted. An adult nasal replica is also studied as a comparison. Monodisperse oleic acid aerosols ranging in size between 2 and 28 μm are delivered into the replica at the rest condition. This size range covers the deposition efficiency up to around 100%. This study also compares results from our previous deposition tests with a 5-year-old replica.

Results: Nasal deposition of micrometer aerosols in small children and infants is higher than that in adults under equivalent breathing conditions, e.g., sitting awake in this study. Combining the data set of infants, children, and adults, we found the deposition in the nasal airway strongly depends on the particle size and pressure drop. The particle deposition can be calculated based on a single empirical equation in all age groups. The intersubject variability within the same age group was not addressed in this study.

Conclusions: An empirical equation for all age groups is developed. From this equation, particle deposition efficiency in the nasal airway can best be estimated with input data of particle size and pressure drop of the airway.