Final answer:
If a client wakes up easily as the nurse enters the room, they were likely in Stage 1 NREM sleep, the lightest and first stage of sleep, where the transition from wakefulness to sleep occurs and individuals are easily awakened.
Step-by-step explanation:
The night nurse knows that if a client wakes up easily, they were most likely in the lightest stage of non-REM (NREM) sleep, known as stage 1 sleep. In this stage, the person is in a transitional phase between wakefulness and deeper sleep, and an individual is much more easily awakened than in the deeper stages. Stage 1 of NREM sleep is characterized by a slowdown in both the rates of respiration and heartbeat, and it involves a marked decrease in brain wave frequency and an increase in amplitude. As we go deeper into sleep, through stages 2 and 3, our brain waves show a characteristic pattern that is different from the Stage 1 pattern and even harder to wake from. Specifically, Stage 2 sleep is identified by sleep spindles and K-complexes, signaling deeper relaxation, while Stage 3 is known for the presence of low frequency, high amplitude delta waves, indicating deep sleep. In contrast, Stage 1 features a mix of alpha and theta waves, which allows for a lighter sleep, making it much easier to wake someone up.