If you’re doing it the way intended you would 100% be aware of your irregular breath or pausing. In fact beginners vipassana often advises counting the breaths individually in a cycle 1..10, and resetting the count when you lose track of your breathing. You intensely focus on the sensation of the air moving through your nostrils, the muscles contracting, your clothing shifting.
However it’s not about controlling your breathing, so it’s not the same as breathing consciously. It’s observing passively. Often you’ll notice that you are breathing irregularly, not because of the meditation, but because you typically are stressed and tight in your musculature due to the way you’re thinking. You can then loosen and reset your patterns of breath to be more natural, deep, and complete.
A goal isn’t to stop with observing the breath though, and you work towards having a total awareness of the entire body at once, shifting your center of existence from your head to the rest of your body. You then incorporate sounds and events in your environment. This requires an intense amount of mental power, and is entirely different from your description of oxygen deprivation. Thought ceases because it interferes with being aware, not because you are experiencing brain death.
