第二，一旦完全进入睡眠状态，非快速眼动期间血液中的二氧化碳增加，氧气减少。

Second, once sleep is fully obtained, there is an increase of carbon dioxide and a decrease of oxygen in the blood that persists during NREM.

youdao

首先，睡眠者在半梦半醒及不同调节机制之间转换时进入睡眠状态，呼吸可能短暂地停止或减少。

First, there may be a brief cessation or reduction of breathing when falling asleep as the sleeper waxes and wanes between sleep and wakefulness and their differing control mechanisms.

youdao

首先会让你进入睡眠状态。

First, we'll put you to sleep when we do all this procedure.

youdao

You start off with a transition period when you're falling asleep. We call that stage I.

一开始是过渡期,你开始进入睡眠状态，这是第一阶段。

耶鲁公开课 - 心理学导论课程节选

First,we'll put you to sleep when we do all this procedure.

首先会让你进入睡眠状态。

耶鲁公开课 - 死亡课程节选