Functional imaging using Computational Fluid Dynamics to assess effect of stimulation of the hypoglossal nerve on upper airway morphology: a pilot study

J.W. De Backer¹, W. G. Vos⁵, Q. Ni², O. Vanderveken³,  P.Parizel⁴, P. Van de Heyning³, W. De Backer⁵

1. FluidDA nv, Antwerp, Belgium 2. Inspire Medical Inc, Minneapolis, US 3. University Hospital Antwerp, Department of ENT, Antwerp, Belgium 4. University Hospital Antwerp, Department of Radiology, Antwerp, Belgium 5. University Hospital Antwerp, Department of Respiratory Medicine, Antwerp, Belgium

Abstract

AIM: To assess the in-vivo effect of stimulation of the hypoglossal nerve on the upper airway morphology using imaging techniques in combination with computational fluid dynamics (CFD) tools.

METHODS: In 8 patients the upper airway was imaged using CT before and during stimulation of the hypoglossal nerve. Changes in airway volume and resistance were determined using segmentation and CFD.

RESULTS:  A statistically significant (p = 0.035) enlargement of the volume for the upper airway at the level near the tongue-base was observed. A significant correlation (R²= 0.89, p=0.002) was found between the change in hydraulic radius and the volume changes in the palatopharynx. No significant correlations were found when considering the upper airway at the tongue base and the resistance parameters. The distance from the upper airway to the mandibula correlated significantly with the change in upper airway volume and with the change in upper airway resistance (R²=0.91, p=0.014).

CONCLUSION: It could be concluded that stimulating the hypoglossal nerve changes the upper airway morphology. A relatively complex motion of the tongue is observed with an enlargement of the airway lumen predominantly near the tongue base. Depending on the volume of the oral cavity, the enlargement is homogeneous or a decrease in CSA occurs at the palatal level. A local decrease in CSA during stimulation results in an increase in upper airway resistance determined using CFD. The distance between the upper airway and the mandibula measured at the level of the glottis appears to be a good surrogate for changes in upper airway resistance.