Effects of Hypoglossal Nerve Stimulation on Upper Airway Structure and Function Using Moving Wall Computational Fluid...

Area of Science:

• Respiratory Medicine
• Biomedical Engineering
• Sleep Science

Background:

• Obstructive sleep apnea (OSA) affects millions, with hypoglossal nerve stimulation (HGNS) offering an alternative to CPAP.
• Treatment efficacy of HGNS varies, and the underlying reasons for these differences are not fully understood.
• Quantifying upper airway structural and functional changes during HGNS is crucial for understanding treatment variability.

Purpose of the Study:

• To propose and validate a novel, non-invasive method using 4DCT and CFD to quantify upper airway changes during HGNS.
• To assess the impact of HGNS on airway cross-sectional area (CSA), neuromuscular work, and airway resistance.
• To explore potential biomarkers for predicting HGNS response in OSA patients.

Main Methods:

• Three male subjects with OSA underwent 4DCT scans during N2 sleep, with and without HGNS, alongside EEG and airflow monitoring.
• Computational fluid dynamics (CFD) simulations were performed using 4DCT-derived anatomy and motion data, coupled with airflow measurements.
• Quantification of airway CSA, neuromuscular work (muscle effort and pressure), and airway resistance was conducted.

Main Results:

• HGNS significantly increased airway CSA by up to 300% and neuromuscular work by up to 490%, primarily in the oropharynx.
• Minute ventilation increased in all subjects (15%-36%), and airway resistance decreased substantially (73%-97%).
• Observed changes in the nasopharynx and hypopharynx varied between individual subjects.

Conclusions:

• The developed 4DCT and CFD methodology effectively quantifies upper airway structural and functional changes induced by HGNS.
• These quantitative parameters may elucidate the variability in HGNS treatment response for OSA.
• Future applications include predicting non-responders, identifying causes of poor response, and optimizing HGNS device titration.