Simulation of nasal cleansing devices

Context

CFD tools can be used to improve the effectiveness of treatment for certain diseases and pathologies. One example is nasal cleansing.

This technique is a major ally in the treatment of nasal and sinus diseases. Nasal cleansing also eliminates secretions and airborne particles that may be deposited on the mucous membranes, whether they have an irritant, allergenic or virological action.

At present, several irrigation techniques are used, such as gravity irrigation, manual irrigation or continuous spray irrigation, without knowing either the characteristics of the water flow during irrigation for each of these methods, or the mechanical washing action of the water on the mucous membranes.

The use of 3D CFD numerical simulation enables us to visualize these flows in the nasal cavities and sinuses, and to establish fields of velocity, pressure, shear stress on the nasal walls, etc. The results enable us to determine which method is best suited to dislodging the residues and particles from the sinuses and airways responsible, for example, for rhino-sinusitis.

Objective

The aim of this study is to quantitatively compare 3 nasal cleansing methods:

1. High-volume gravity irrigation,
2. High-volume irrigation with manual pressure,
3. Continuous spray.

Numerical comparison of nasal cleansing by high-volume irrigation, with manual pressure or in gravity mode, on a healthy patient.

Simulation and results

OptiFluides ran 3D simulations to characterize irrigation with each of the above-mentioned methods, and to determine the physical parameters associated with each: shear stress, wetted surface, water contact time, etc.

The CFD model simulates incompressible transient flow. The use of the Volume of Fluid (VoF) model enabled us to model two-phase flow with air and water phases, and to visualize the evolution of the water/air interface during washing.

These simulations showed that high-volume irrigations, whether using manual pressure or gravity, cover the entire nasal cavity and sinuses, rapidly and with greater shear stress on the nasal tissues, enabling more effective cleansing. Continuous spray irrigation is more localized, not covering all areas, and less abrasive. The much smaller volumes injected make it gentler on the patient, but the process is slower and generates less shear stress.

The characterization of nasal cleansing devices by numerical simulation is still in the development phase, and has not yet reached its full potential. For example, although we are able to determine the shear forces generated by the water on the mucous membranes, the “threshold” values for the removal of impurities are not yet known, and it is therefore not possible to determine whether the device is too abrasive or too non-abrasive. These initial simulations provide both answers and new questions for our knowledge of nasal cleansing.