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    Interventional procedure overview of daytime intraoral neuromuscular electrical tongue stimulation using a removable device for obstructive sleep apnoea

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    Outcome measures

    The main outcomes include the change in the percentage of time spent snoring, respiratory parameters (AHI and ODI), sleep quality questionnaires (ESS and PSQI), and snoring intensity (VAS). Objective snoring (change in the percentage of time spent snoring) and respiratory parameters were recorded with 2 consecutive night home sleep studies before and after the procedure. A 20% reduction in snoring time was considered a clinically relevant change. In terms of sleep quality questionnaires, both patients and their bed partners completed the PSQI and ESS before, and at the end of, the therapy. The VAS was recorded daily by bed partners and its evaluation was based on the average rating over 2 weeks: pretherapy (2 weeks), end of the therapy (the last 2 weeks), and posttherapy (2 weeks). The key measures used are detailed in the following paragraphs.

    The AHI is an index used to indicate the severity of sleep apnoea. It is represented by the number of apnoea and hypopnea events per hour of sleep. The AHI values for adults are categorised as:

    • Normal: AHI of less than 5 events per hour

    • Mild sleep apnoea: AHI of 5 or more but less than 15 events per hour

    • Moderate sleep apnoea: AHI of 15 or more but less than 30 events per hour

    • Severe sleep apnoea: AHI of 30 or more events per hour

    The minimal clinically important difference in AHI is determined as 5 events per hour.

    The ESS is a self-reported questionnaire which measures daytime sleepiness. The test includes 8 situations, with each situation being rated from 0 (no chance of dozing or sleeping) to 3 (high chance of dozing or sleeping). A total score is based on a scale of 0 to 24:

    • 0 to 5 lower normal daytime sleepiness

    • 6 to10 normal daytime sleepiness

    • 11 to 12 mild excessive daytime symptoms

    • 13 to 15 moderate excessive daytime symptoms

    • 16 to 24 severe excessive daytime symptoms

    The minimal clinically important improvement of the ESS lies between -2 and -3.

    The ODIis a measure of insufficient blood oxygen during sleep. A normal oxygen saturation level is about 96% to 97%. When blood oxygen levels drop below 90%, ODI is considered abnormal. ODI can be used to measure the average number of desaturation episodes per hour. Desaturation episodes are generally described as a decrease in the mean oxygen saturation of 4% or more (over the last 120 seconds) that lasts for at least 10 seconds. An ODI more than 5 often predicts an AHI more than 5.

    The PSQI is a self-rated questionnaire which assesses sleep quality and disturbances over a month. The measure consists of 19 individual items, creating 7 components: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. The sum of scores for these 7 components yields 1 global score ranging from 0 to 21, where lower scores indicate a healthier sleep quality.

    The VAS is used to rank the impact of snoring by bed partners from 1 (no snoring) to 10 (intolerable snoring).