Interacting effects of genioglossus stimulation and mandibular advancement in sleep apnea

Abstract

Oliven A. Interacting effects of genioglossus stimulation and mandibular advancement in sleep apnea. J Appl Physiol 106: 1668-1673, 2009. First published February 19, 2009 doi:10.1152/japplphysiol.91501.2008 and stimulation of the genioglossus (GG) have been shown to improve upper airway patency, but neither one achieves the effect of continuous positive airway pressure (CPAP) treatment. In the present study we assessed the combined effect of MA and GG stimulation on the relaxed pharynx in patients with obstructive sleep apnea (OSA). We evaluated responses of upper airway pressure-flow relationships and endoscopically determined pharyngeal cross-sectional area to MA and electrical stimulation of the GG in 14 propofol-anesthetized OSA patients. Measurements were undertaken at multiple levels of CPAP, enabling calculation of the critical closing pressure (Pcrit), upstream resistance (Rus), and pharyngeal compliance. GG stimulation, MA, and the combination of both shifted the pressure:flow relationships toward higher flow levels, resulting in progressively lower Pcrit (from baseline of 2.9 Ϯ 2.2 to 0.9 Ϯ 2.5, Ϫ1.4 Ϯ 2.9, and Ϫ4.2 Ϯ 3.3 cmH2O, respectively), without significant change in Rus. ⌬Pcrit during GG stimulation was significantly larger during MA than under baseline conditions (Ϫ2.8 Ϯ 1.4 vs. Ϫ2.0 Ϯ 1.4 cmH 2O, P ϭ 0.011). Combining the effect of GG stimulation with MA lowered Pcrit below 0 in all patients and restored pharyngeal patency to a level that enabled flow above the hypopnea level in 10/14 of the patients. Velopharyngeal compliance was not affected by either manipulation. We conclude that the combined effect of MA and GG stimulation is additive and may act in synergy, preventing substantial flow limitation of the relaxed pharynx in most OSA patients.

The Combination of Supplemental Oxygen and a Hypnotic Markedly Improves Obstructive Sleep Apnea in Patients with a Mild to Moderate Upper Airway Collapsibility

“…Similarly, Dieltjens et al 38 demonstrated the additional reduction in OSA severity patients experienced when sleeping in the lateral position was done in conjunction with wearing an oral appliance. Last, Oliven et al 39 assessed the effect of a combination of electrical stimulation of the genioglossus with mandibular advancement (targeting muscle responsiveness and anatomy/collapsibility respectively) on the Pcrit in 14 OSA patients under propofol-induced anesthesia. Although the authors did not assess the effect of these interventions on OSA severity, their findings indicate that there was an additive improvement in Pcrit compared with individual manipulations, with a number of patients in the combination group achieving a Pcrit ≤ 5 cmH2O, which should lead to a resolution of OSA.…”

Acute Upper Airway Responses to Hypoglossal Nerve Stimulation during Sleep in Obstructive Sleep Apnea

“…These increases have been attributed to decreases in pharyngeal collapsibility (14,16,17), which decreases the back pressure to inspiratory airflow (27). In previous studies, stimulating the genioglossus muscle and hypoglossal nerve led to an approximately 3-to 5-cm H 2 O decrease in critical pressure, which can account for an approximately 150-to 250-ml/s increase in maximal inspiratory airflow (18,19).…”

“…In these prior studies, investigators scrutinized EEG and ECG signals to exclude responses associated with cortical or autonomic activation (13,18,19). Additional studies with implantable nerve cuff (13) and fine-wire electrodes have demonstrated responses to selective lingual muscle stimulation during sleep and anesthesia (13)(14)(15)(16)(17). The present study also screened for evidence of cortical and autonomic activation, and further required strict temporal synchrony between the stimulus burst and airflow response to exclude arousal responses from the analysis.…”

“…Implantable HGNS systems have been developed to stimulate the hypoglossal nerve during inspiration, and recruit the lingual musculature, leading to decreases in pharyngeal collapsibility during sleep (14)(15)(16)(17). Motor activity protrudes the tongue, and mitigates airflow obstruction during sleep (18,19).…”

Parameters affecting pharyngeal response to genioglossus stimulation in sleep apnoea

“…We did not evaluate systematically the reproducibility of our results, but current and previous experience based on insertion of additional electrodes in the same area of stimulation suggests that the effects of stimulation are closely reproducible. Small changes in the level of anaesthesia, as well as head or mandibular position known to affect the response to GG contraction [33], could occur between the evaluations of the two sites of stimulation, despite our efforts to maintain stable conditions. However, the two sites were evaluated in random order to prevent systematic error.…”