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Hypnogram

Method: – Hypnograms are obtained by visually scoring EEGs, EOGs, and EMGs. – Certain frequencies displayed by EEGs, EOGs, and EMGs determine the sleep or […]

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Method:
– Hypnograms are obtained by visually scoring EEGs, EOGs, and EMGs.
– Certain frequencies displayed by EEGs, EOGs, and EMGs determine the sleep or wake stage.
– AASM protocol defines sleep scoring in 30-second epochs.
– Prior to AASM, RK rules classified sleep stages.
– Hypnograms vary based on age, emotional state, and environmental factors.

Output:
– Normal sleep consists of REM and non-REM stages.
– Healthy adults need 7-9 hours of sleep per night.
– Healthy adults spend 20-25% of sleep in REM.
– Sleep cycles are around 90 minutes with 4-6 cycles per major sleep period.
– SWS occurs mostly in the first one or two cycles of sleep.

Disrupted sleep:
– Hypnograms show irregular sleeping patterns in sleep disorders.
– Hypnograms can detect disruptions in sleep stage transitions.
– Medications like Phenytoin and Gabapentin impact sleep architecture.
– OSA disrupts REM-NREM stage transitions.
– Hypnograms visualize the effects of medications on sleep.

Analysis:
– Hypnograms visually represent each sleep stage’s time period.
– Hypnograms are mainly qualitative but can be statistically evaluated.
– Multistate survival analysis and log-linear models provide numerical significance.
– Hypnograms are not commonly used for quantitative data.
– Statistical evaluation can enhance the significance of hypnogram data.

Limitations:
– Hypnograms record events in 30-second epochs, limiting microstructure evaluation.
– Hypnogram results smooth out the natural sleep process.
– Features like sleep spindles may not be defined in hypnograms.
– Hypnograms may misrepresent sleep stages due to overlapping features.
– Data for hypnograms is limited to input from EEG, EOG, or EMG.

Research directions:
– Improve automated hypnogram output by incorporating ECG measurements.
– Enhance sleep analysis quality by combining hypnograms with color density spectral arrays.

Hypnogram (Wikipedia)

A hypnogram is a form of polysomnography; it is a graph that represents the stages of sleep as a function of time. It was developed as an easy way to present the recordings of the brain wave activity from an electroencephalogram (EEG) during a period of sleep. It allows the different stages of sleep: rapid eye movement sleep (REM) and non-rapid eye movement sleep (NREM) to be identified during the sleep cycle. NREM sleep can be further classified into NREM stage 1, 2 and 3. The previously considered 4th stage of NREM sleep has been included within stage 3; this stage is also called slow wave sleep (SWS) and is the deepest stage of sleep.

Example hypnogram for a normal, healthy adult. Within the first hour of sleep SWS is displayed. Cycles of REM and NREM sleep proceed. During the third cycle of sleep there are two brief wake states. During the second half of the sleep period more REM sleep is displayed and there is little SWS detected.
Example hypnogram of a normal, healthy adult
Here, both stage 3 and stage 4 are shown; these are often combined as stage 3.
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