Comment by ayhanfuat

That caused me nightmares when I was first diagnosed with sleep apnea. I would check my oxygen levels during the sleep to see if my treatment is effective. Even though the CPAP machine would show a few short events Apple Watch would show levels as low as 75%. Thankfully in my next sleep study I learned that my oxygen levels were consistently above 95% and the watch is indeed very unreliable (how snug it is, which direction it is facing etc highly affect the results).