Correlations to Estimate the Key Anatomical Dimensions of Pediatric Nasal Airways using Minimally Invasive Measurements of Intranasal Pressure Gradient

Abstract

Background: Understanding the morphology of nasal airways is important in determining the nasal airway deposition of inhaled aerosol. Moreover, objective assessment of the anatomy of human nasal airways is useful to develop a database of reference or normal values as a resource to investigate anatomical abnormalities of airways. Current methods for the objective assessment of the nasal airways are either limited to very few dimensions or can only be performed by specialized researchers. Thus, the main objective of this study was to determine the correlations between the intranasal pressure gradient (Δp) and the key anatomical dimensions of the pediatric nasal airways, which could in turn allow the extrapolation of nasal airway morphology based on simple minimally invasive measurements of pressure. Methods: The anatomical data and Δp were obtained from in vitro studies with nasal airway models of 11 infants ages 3-18 months and 13 children ages 4-14 years old. Key anatomical dimensions were identified based on both rhinology and aerosol dosimetry literature. These anatomic data, including the volume, V, surface area, A_s, length, L, and the minimum cross-sectional area of the replicas, A_min, were then analyzed for correlation with Δp and flow parameters, using Bernoulli's principle and dimensional analysis. Results: Strong correlations were found between Δp and A_s/L for children, and between Δp and V/A_s for infants. Additional pressure gradient correlations were developed with A_min, V/A_s, $\sqrt{V∕L}$, and L. Conclusions: The correlations identified between anatomic data and Δp have clinical implications in pediatric rhinology, suggesting that certain aspects of airway anatomy in infants and children can be predicted through the measurement of Δp. The airway dimensions, predicted using Δp measurement, may be used in tandem with aerosol nasal deposition correlations that account for nasal airway dimensions.

Keywords: evaluation and diagnosis; intranasal deposition of aerosol; intranasal pressure gradient; nasal resistance; otolaryngology disorders; pediatric nasal anatomy.