[Electrical stimulation of the genioglossus to improve pharyngeal patency in obstructive sleep apnea: comparison of results obtained during sleep and anesthesia].

Contraction of the geniogtossus (GG) has been shown to improve upper airway patency in patients with sleep apnea during sleep and anesthesia. However, a large variability in response exists, requiring selection of adequate patients if GG stimulation should be used as a treatment modality. In the present study, we compared responses in upper airway pressure-flow relationships to electrical stimulation of the GG in patients with obstructive sleep apnea during sleep and mild anesthesia. Nine patients studied during sleep were matched with 9 patients evaluated during propofol anesthesia. Stimulation was performed with fine wire electrodes inserted near the mandibular insertion of the GG. Airflow was measured at muLtiple levels of CPAP, and upper airway collapsibility was defined by the pressure below which airflow ceased (the "critical" pressure, Pcrit). ELectrical stimulation shifted the pressure-flow reLationships toward higher flow Levels in all patients over the entire range of CPAP applied. Pcrit decreased significantly during stimulation-induced contraction of the GG, and similarly in the patients evaluated during sleep and during anesthesia (from 1.6 +/- 2.0 to -1.6 +/- 2.5, and from 1.8 +/- 1.8 to -0.2 +/- 1.8 cmH2O, during steep and anesthesia, respectively, p < 0.01, without a significant change in upstream resistance. Our findings imply that responses in Pcrit to electrical stimulation of the main tongue protrusor during propofoL anesthesia may reflect those observed during sleep, and evaluation of the response of sleep apnea patients to GG stimulation can be evaluated during short anesthesia.

Interacting effects of genioglossus stimulation and mandibular advancement in sleep apnea.

Both mandibular advancement (MA) 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 +/- 2.2 to 0.9 +/- 2.5, -1.4 +/- 2.9, and -4.2 +/- 3.3 cmH(2)O, respectively), without significant change in Rus. DeltaPcrit during GG stimulation was significantly larger during MA than under baseline conditions (-2.8 +/- 1.4 vs. -2.0 +/- 1.4 cmH(2)O, P = 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.