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Figure 1 | Critical Care

Figure 1

From: Intensive care unit depth of sleep: proof of concept of a simple electroencephalography index in the non-sedated

Figure 1

Hypnogram and IDOS index of the same recording. To illustrate the resemblance of the visually scored R&K (1A) hypnogram and IDOS index (1B), an example is shown. This recording shows normal sleep and is one of the 15 datasets used for further comparison. The hypnogram resulting from R&K analysis (1A) shows a long period of wake EEG with occasional transitional sleep. Towards midnight the EEG transitions to increasingly deep stages of sleep, before gradually resurfacing to shallow stages of sleep. This process is repeated roughly four times, known as ultradian rhythm. The IDOS index (1B) of the same recording shows similar transitions of depth of sleep. Simple linear thresholds are manually selected to define the transition from wake (blue) to sleep (red) and the transition to SWS (green). The same method of classification has been applied to all fifteen non-ICU recordings and all five ICU recordings. EEG, electroencephalogram; IDOS, ICU Depth of Sleep; R&K, Rechtschaffen and Kales; SWS, slow wave sleep.

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