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Deep Sleep
Refers to combined non-REM sleep stages 3 and 4 in sleep studies
Delayed sleep phase
A condition occurring when the clock hour at which sleep normally occurs is moved back in time in a given, 24 hour sleep-wake cycle. The result is a temporarily displaced (delayed) occurrence of sleep within the 24 hour cycle.
Delta sleep
Stage(s) of sleep in which EEG delta waves are prevalent or predominant (sleep stages 3 and 4, respectively).
Delta waves
EEG activity with a frequency less than 4 Hz. In human sleep stage scoring, conventionally the minimum criteria for scoring delta waves is 75 uV (peak-to-peak) amplitude, and 0.5 second duration (2 Hz).
Diagnostic Sleep Study
Monitoring of several physiological activities in a sleeping individual. Usually performed to determine the absence or presence of a specific sleep disorder. The sleep study can occur in a sleep disorders center or in a patient's home with portable recording equipment.
Diaphragm
Large, concave muscle attached to the rib cage at bottom of the chest (top of the abdomen). Inhalation occurs when diaphragm contracts. Exhalation is passive as the muscle relaxes.
Diurna
Lactive and wakeful in the daytime versus active in the nighttime
DME - Durable Medical Equipment
Equipment such as wheelchairs and walkers which are prescribed for use by or on the order of a physician, also includes CPAP and BI-Level machines.
Drowsiness
Drowsyquiet wakefulness occurring prior to sleep onset.
Dyssomnia
A disorder of sleep or wakefulness; not a parasomnia
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