Sleep Definitions Dictionary N through Z

Normal Sleep -- Normal sleep % are: Stage 1 - 5%; Stage 2 - 55%; Stage 3/4 - 20%; REM - 20%. Stage 1 is only a transition state from wake to stage 2 and has no real rest value. A lot of it means inability to initiate and/or maintain sleep. Stage 3/4 (SWS) decreases as a function of age, or if you're subject to constant arousals, as in OSA. There are strict criteria to score SWS, so one may still be having some SWS-like activity, but can't be scored as such because it fails to meet scoring criteria, such as waveform height (amplitude). (Sleepydave)

Oxygen Saturation -- Oxygen Saturation: Oxygen content of blood divided by oxygen capacity and expressed in volume percent. (JSD); Normal Oxygen Saturation (SaO2) is >94%. (Sleepydave)

Sleep Efficiency -- Sleep Efficiency (or Sleep-Efficiency Index): The proportion of sleep in the episode potentially filled by sleep (i.e., the ration of total sleep time to time in bed) or Sleep Efficiency = Total sleep time multiplied by time in bed. (JSD); Normal sleep efficiency is at least 85% (asleep 85% of the night). It is reduced in a number of situations, such as insomnia or simply lab effect. (Sleepydave)

Sleep Latency -- Sleep Latency: The duration of time from ‘lights out,’ or bedtime, to the onset of sleep. (JSD); Normal sleep latency is about 15 minutes, REM latency is 90 minutes, so those are OK. (Sleepydave)

Spontaneous Arousal Index -- Spontaneous Arousal Index: The number of spontaneous arousals (e.g. arousals not related to respiratory events, limb movements, snoring, etc) multiplied by the number of hours of sleep. (JSD); An arousal is a wake or "alpha" pattern for 3 to 15 seconds. You are usually not aware of arousals. As you suggest, there are 3 types of arousals reported out on the sleep studies- those attributed to respiratory events, periodic limb movements and those that are spontaneous. Spontaneous arousals have no directly attributable cause, or cannot be linked to the first 2 reasons for arousals. That said, there may be respiratory events during sleep that generate "spontaneous" arousals. like snores or flow limitations. Indeed, the whole Upper Airway Resistance Syndrome is based on the presence of a large number of spontaneous arousals without the presence of scorable respiratory events such as hypopneas or apneas. Technically, they should be identified using an esophageal ballon to measure negative inspiratory pressure (which just about nobody does) or a nasal or oro-nasal pressure transducer, and look for flow limitations. These are RERAs (Respiratory Effort-Related Arousals). If you take this number, RERA, and add it to the AHI, you have the Respiratory Disturbance Index (RDI). There are a bunch of things that could create the scenario for the appearance of a large number of truly spontaneous arousals, such as medications that deter sleep (pseudoephedrine, caffeine, some antidepressants, too much thyroid medication, etc.), depression and narcolepsy. (Sleepydave)