Upper airway response to electrical stimulation of the genioglossus in obstructive sleep apnea

Contraction of the genioglossus (GG) has been shown to improve upper airway patency. In the present study, we evaluated responses in upper airway pressure-flow relationships during sleep to electrical stimulation (ES) of the GG in patients with obstructive sleep apnea. Five patients with chronically implanted hypoglossal nerve (HG) electrodes and nine patients with fine-wire electrodes inserted into the GG were studied. Airflow was measured at multiple levels of nasal pressure, and upper airway collapsibility was defined by the nasal pressure below which airflow ceased ["critical" pressure (Pcrit)]. ES shifted the pressure-flow relationships toward higher flow levels in all patients over the entire range of nasal pressure applied. Pcrit decreased similarly during both HG-ES and GG-ES (DeltaPcrit was 3.98 +/- 2.31 and 3.18 +/- 1.70 cmH(2)O, respectively) without a significant change in upstream resistance. The site of collapse (velo- vs. oropharynx) did not influence the response to GG-ES. Moreover, ES-induced reductions in the apnea-hypopnea index of the HG-ES patients were associated with substantial decreases in Pcrit. Our findings imply that responses in apnea severity to HG-ES can be predicted by characterizing the patient's baseline pressure-flow relationships and response to GG-ES.