Tage ngủ III là ghi bàn khi EEG có biên độ sóng chậm cao chiếm ít nhất 20% nhưng không quá 50% của thời đại. Sóng chậm là 2 Hz hoặc chậm hơn và phải có một đỉnh cao đến đỉnh điểm biên độ của ít nhất 75 μV. Ngủ cọc, K phức hợp, và sóng đỉnh có thể hoặc không thể có mặt trong giai đoạn này của ngủ. | CHAPTER 6 FIGURE . This is a 30-sec epoch demonstrating stage III sleep with slow waves present thin arrows that do not encompass more than 50 of the epoch. Additionally sleep spindles are noted thick arrow as are vertex waves dashed arrow . Stage III sleep is scored when the EEG has high-amplitude slow waves occupying at least 20 but no more than 50 of the epoch. Slow waves are 2 Hz or slower and must have a peak to peak amplitude of at least 75 pV. Sleep spindles K complexes and vertex waves may or may not be present in this stage of sleep. 162 Polysomnography FIGURE . This is a 30-sec epoch demonstrating stage IV sleep and high-amplitude delta waves thin arrows that are often seen in the eye leads as well thick arrows . In stage IV sleep slow waves encompass at least 50 of the epoch. Slow waves are defined the same way as in stage III sleep. Sleep spindles K complexes and vertex waves may or may not be present in stage IV sleep. Many PSG laboratories score stages III and IV together as differentiation between the two stages is difficult and is referred to as stage delta delta sleep or slow- wave sleep. Most of the delta waves above are greater than 100 pV. Delta waves can be differentiated from eye movements because these waves are in phase and eye movements are out of phase in the eye leads. EMG activity is low in delta sleep however not as low as in REM sleep. 163 CHAPTER 6 FIGURE . This is a 30-sec epoch demonstrating stage REM with frequent rapid eye movements thin arrows atonia thick arrow and mixed-frequency EEG dashed arrow . Stage REM is characterized by the appearance of low-amplitude mixed-frequency EEG activity EMG atonia and rapid eye movements. EEG activity is similar to that seen in stage I sleep however vertex waves are much less common. Although EMG atonia is characteristic in stage REM occasional phasic EMG bursts may be seen. If EMG atonia is not noted the EMG must be at the lowest level compared to other stages of sleep relative .
