Think of your oxygen saturation (SpO2) like a lazy river, not a flat highway. When you’re awake, it usually hangs out around 95 to 100 percent. But once you drift off, it can dip a tiny bit, and that’s expected.
Why? Because your breathing slows down, and your body’s “drive to breathe” chills out. It’s like your lungs are saying, “We’re on break, boss.”
Sleep Stages: The Real Drivers
Your sleep isn’t a single block—it cycles through stages. Light sleep and deep sleep both tweak your oxygen, but in different ways. In deep sleep, your breathing is super steady, like a purring cat. In light sleep—and especially REM sleep—things get a little messy.
REM is when you dream. Your brain is buzzing, but your body is paralyzed (to keep you from acting out your dreams). Your breathing becomes irregular, and your oxygen can momentarily dip—like a hiccup in the river.
