Impulse Configuration in Hypoglossal Nerve Stimulation in Obstructive Sleep Apnea: The Effect of Modifying Pulse Width and Frequency

Neuromodulation. 2021 Jul 2. doi: 10.1111/ner.13490. Online ahead of print.

Abstract

Objectives: Hypoglossal nerve stimulation is an effective treatment option for obstructive sleep apnea (OSA) in positive airway pressure therapy failure. Nonetheless, data regarding the functional effect of modifying stimulation parameters within each electrode configuration are limited.

Materials and methods: In a retrospective study of 76 patients with 12 months or more follow-up, functional tongue protrusion thresholds were compared for pulse width and frequency configurations of 90 μsec 33 Hz vs 120 μsec 40 Hz. The number of tolerated voltage amplitude steps between sensation, functional, and subdiscomfort thresholds were assessed for both settings as well as impedances.

Results: The overall cohort showed improvement in OSA metrics: median apnea-hypopnea index from 30.0/hour to 18.6/hour and Epworth Sleepiness Scale from 13.5 to 7.6. For both bipolar and unipolar electrode configurations, the stimulation amplitude required for functional tongue protrusion was significantly reduced when the pulse width and frequency were converted from 90 μsec 33 Hz to 120 μsec 40 Hz (p < 0.001). Nevertheless, the number of voltage amplitude steps from sensation, functional, to subdiscomfort thresholds did not differ between the two settings. The ratio of automatically derived impedances between bipolar and unipolar electrode configurations was relevantly correlated with the ratio of functional thresholds at these parameters.

Conclusion: Changing the stimulation parameters may lower the voltage requirements while maintaining the same effect on tongue protrusion. Changing these stimulation parameters does not affect the range of tolerated impulse steps between functional and subdiscomfort thresholds. Future technical appliances could help estimate functional thresholds at different electrode configurations for each patient by automatically measuring impedances.

Keywords: hypoglossal nerve stimulation; impedance; impulse configuration; long-term outcome; sleep apnea.