Effects of Anatomy and Particle Size on Nasal Sprays and Nebulizers

Abstract

Objective To study the effects of nasal deformity on aerosol penetration past the nasal valve (NV) for varying particle sizes using sprays or nebulizers. Study Design Computed mathematical nasal airway model. Setting Department computer lab Subjects and Methods Particle deposition was analyzed using a computational fluid dynamics model of the human nose with leftward septal deviation and compensatory right inferior turbinate hypertrophy. Sprays were simulated for 10µm, 20µm, 50µm, or particle sizes following a Rosin Rammler Particle Size Distribution (10–110µm), at speeds of 1m/s, 3m/s, or 10m/s. Nebulization was simulated for 1µm, 3.2µm, 6.42µm, or 10µm particles. Steady state inspiratory airflow was simulated at 15.7L/min. Results Sprays predicted higher NV penetration on the right side for particle sizes >10µm, with comparable penetration on both sides at 10µm. Nearly 100% deposited in the nasal passages for all spray characteristics. Nebulizer predictions showed nearly 100% of particles <6.42µm and over 50% of 6.42µm bypassing both sides of the nose without depositing. Of the nebulized particles that deposited, penetration was higher on the right at 10µm, with comparable penetration on both sides at 6.42µm. Spray penetration was highest at 10µm, with over 96% penetrating on both sides at 1 and 3m/s. Nebulization penetration was also highest at 10µm (40% on the left, >90% on the right). Conclusion In the presence of a septal deviation, sprays or nebulizers containing 10µm particles may have good penetration beyond the NV. Nebulized particles <10µm are likely to be respirable. Additionally, spray speeds above 3m/s may limit penetration.

A Computational Study of Nasal Spray Deposition Pattern in Four Ethnic Groups

“…(52) The choice of 1 m/s spray velocity was determined based on an earlier report by Frank et al (8) that showed higher nasal spray penetration at 1 m/s compared to 3 m/s and 10 m/s.…”

“…In particular, the presence of nasal anatomic deformities such as septal deviation has been reported to severely impede particle deposition. (6)(7)(8) Similarly, normal paranasal sinuses are usually altered by chronic rhinosinusitis, and management of this disease requires a combination of medical and surgical therapies. (31)(32)(33)(34)(35) Following sinus surgery, topical nasal drug medication is often prescribed to prevent recurrent disease.…”

Influence of Mesh Density on Airflow and Particle Deposition in Sinonasal Airway Modeling

“…There is a lack of consistency in the literature on the number and type of grid elements required to provide numerically accurate CFD solutions for studies involving sinonasal insilico analysis of airflow and particulate matter, (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) even though most investigators performed airflow simulation using the finite volume method software package, FluentÔ (ANSYS, Inc., Canonsburg, PA). Among studies where mesh density analyses were reported, some authors failed to report details regarding how mesh refinement was done to achieve grid-independent numerical solutions.…”

“…(8)(9)(10)(11)(12)18) In situations where particle transport was simulated (Table 1), the mesh structure utilized varied; some authors utilized unstructured tetrahedral meshes, (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)19,20) whereas other investigators used a hybrid of tetrahedral and prism meshes. (1)(2)(3)(14)(15)(16)(17)(18)21,22) The inclusion of prism boundary layers increases mesh density near airway walls and is generally considered to provide more accurate near-wall particle trajectory calculations.…”

“…(2,3,13,17,20) A number of other investigators did not specify the variables computed to determine grid independent control volume. (1,(8)(9)(10)(11)14,15) (3) There are no standardized nasal characteristics that investigators conform to when reconstructing nasal geometry for CFD studies. In some articles, CFD analyses were done using unilateral (one side) nasal cavity, (8)(9)(10)(11)21,22) while others performed CFD on bilateral (two sides) nasal cavities without the paranasal sinuses (1)(2)(3)6,(13)(14)(15)(17)(18)(19)(20) or with the paranasal sinuses; as in this study or that of Ge et al (16) The present study uses CFD techniques to systematically perform a two-stage mesh sensitivity analysis in an anatomically accurate 3D sinonasal cavity of a subject who underwent functional endoscopic sinus surgery (FESS) as part of treatment for medically recalcitrant chronic rhinosinusitis (CRS).…”