Table 1. Summary of the studies on submental transcutaneous stimulation.
| Study | Type of stimulation | Type of electrodes | Study design | N | Current | Frequency (Hz) | Pulse width (μs) | Outcomes |
|---|---|---|---|---|---|---|---|---|
| Miki et al. [1989] (22) | Intermittent stimulation without event association | Surface stimulation bipolar electrodes (10 mm diameter) were attached to the skin under the chin at the submental region | Uncontrolled, open label, single arm study | 6 | 15-40 V | 50 | n/a | The apnoea index, apnoea time/total sleep time, longest apnoea duration, and the number of times per hour that oxygen saturation dropped below 85% decreased significantly on stimulation |
| Edmonds et al. [1992] (23) | Intermittent stimulation (1-6 seconds on, 1-8 seconds off) for periods ranging from 5 to 45 minutes followed by periods of no stimulation | Submental electrodes in two patients, submental and subhyoid electrodes in six patients | Uncontrolled, open label, single arm study | 8 | 15-39.6 mA | 50 | n/a | Failure to prevent or improve either sleep-disordered breathing or sleep architecture |
| Hida et al. [1994] (25) | Manual stimulation at each respiratory event | Two silver electrodes (10 mm diameter) attached in the proximal half of the submental region | Uncontrolled, open label, single arm study | 13 | 5-30 V | 100 | n/a | Reduction in apnoea index, improvement in apnoea duration and oxygen saturation |
| Guilleminault et al. [1995] (26) | Manual stimulation at each respiratory event for 15 events | 6 electrodes fitted in a MAD for intra-oral stimulation and bilateral electrodes each side for submental stimulation | Uncontrolled, open label, single arm study | 7 | 3-6 mA (10-20 V) | 50 | 80 | No changes in number of apnoeas or oxygen saturation. |
| Hu et al. [2008] (27) | Triggered stimulation (apnoea sensor) after 5 s of no oronasal airflow. | Submental electrodes | Uncontrolled, open label, single arm study | 22 | 12-80 V | 50 | n/a | Reduction of RDI, amelioration of oxygen saturation |
| Steier et al. [2011] (28) | 10 minutes continuous bilateral stimulation | Submental, two 4 cm x 4 cm patches | Uncontrolled, open label, single arm study | 11 | 10.1 (3.7) mA | 30 | 250 | Reduction of AHI and RDI, improvement of oxygen saturation, reduction of snoring |
N, number of patients; V, volt; mA, milli-Ampere; Hz, Hertz; n/a, not applicable or not available; MAD, mandibular advancement device; RDI, respiratory disturbance index; AHI, apnoea hypopnoea index. Data on current indicate the range (in brackets), except for the study by Steier et al. where it indicates mean (standard deviation).