Table 2. Summary of the studies on hypoglossal nerve stimulation.
| Study | Sponsor | Type of stimulation | Design of the study | N | Current | Frequency (Hz) | Pulse width (μs) | Main findings | Reduction in mean AHI | Percentage reduction (%) |
|---|---|---|---|---|---|---|---|---|---|---|
| Schwartz et al. [2001] (39) | Inspire I, Medtronic Inc. | Triggered inspiratory stimulation with 1 sensing lead | Non randomised, uncontrolled prospective study | 8 | 2.2-3.0 V | 33.9-37.7 | 94.3-110.5 | REM and NREM AHI reduction and improvement in nocturnal oxygen saturation after 6 months (means are averaged over the 1-, 3- and 6-month follow up nights) | NREM AHI from 52 [20.4]/h to 22.6 [12.1]/h | –56.5 |
| REM AHI from 48.2 [30.5]/h to 16.6 [17.1]/h | –65.5 | |||||||||
| Eastwood et al. [2011] (38) | Apnex Medical Inc. | Triggered stimulation with 2 sensing leads | Single arm open label study | 21 | n/a | n/a | n/a | Improvements of symptoms and AHI after 6 months | AHI from 43.1 [17.5]/h to 19.5 [16.7]/h | –54.7 |
| Schwartz et al. [2012] (37) | Apnex Medical Inc. | Triggered stimulation with 2 sensing leads | Non randomised, uncontrolled prospective study | 30 | 0-4 mA (variable) | 40 (fixed) | 60-90 (variable) | Increase in inspiratory airflow with increasing stimulation intensity | n/a | n/a |
| Van de Heyning et al. [2012] (40) | Inspire II, Medtronic Inc. | Triggered inspiratory stimulation with 1 sensing lead | Open prospective studies (part 1: broad selection criteria, part 2: using selection criteria derived from the experience) | 22 (part 1) 8 (part 2) | n/a | n/a | n/a | Improvement of AHI, daytime symptoms and quality of life at 6 months | AHI from 38.9 [9.8]/h to 10.0 [11.0]/h | –74.3 |
| Mwenge et al. [2013] (36) | ImThera Medical Inc. | Cyclical, non triggered stimulation | Open label, single arm study | 13 | n/a | n/a | n/a | Improvement of AHI and mean oxygen saturation at 12 months | AHI from 45 [18]/h to 21 [17]/h | –53 |
| Strollo et al. [2014] (41) | Inspire, Medtronic Inc. | Triggered inspiratory stimulation with 1 sensing lead | Non randomised, uncontrolled trial with randomised withdrawal study in responders | 126 | n/a | n/a | n/a | Improvement of AHI (median from 29.3/h to 9.0/h which equals 68%), ODI (reduction in median 70%), daytime symptoms and quality of life at 12 months | AHI from 32.0 [11.8]/h to 15.3 [16.1]/h | –52.1 |
N, number of patients; V, volt; mA, milli-Ampere; Hz, Hertz; n/a, not applicable or not available; REM, rapid eye movement; NREM, not rapid eye movement; AHI, apnoea hypopnoea index; ODI, oxygen desaturation index. All data on the AHI are presented as mean and (standard deviation) and the percentage of reduction is calculated from the raw data.