I stumbled across breathing techniques a while ago and have been experimenting with them. I have found out that breathing techniques before sleep almost always induce beautiful vivid lucid dreams for me and have heard similar experiences from others. I thought I'd share this and thought it may be of interest to some.
I believe that high levels of oxygen in your body and the process of breathing increases DMT production. The synthesizing enzyme of DMT can be found with the highest levels in the lungs, thyroid, and adrenal gland. Those are some of the places intense breathing stimulates. It is also possible that intense breathing techniques can force oxygenated blood into the brain and stimulate pineal gland to produce DMT.
"Rick Strassman, an author and Clinical Associate Professor of Psychiatry at the University of New Mexico School of Medicine, has theorised that the human pineal gland is capable of producing the hallucinogen N,N-dimethyltryptamine (DMT) under certain circumstances.[58] In 2013 he and other researchers first reported DMT in the pineal gland microdialysate of rodents -Wikipedia"
As I read, you cannot increase the blood oxygen levels by breathing more or anything, as your red blood cells anyways are almost fully saturated on normal breathing. What you can do is by increasing the oxygen partial pressure in the air, to increase the blood plasma oxygen levels. But for this you need air with more oxygen in it or with a higher pressure. Thats where the breathing techniques come in. There are many methods that have the same effects Wim Hof's Breathwork technique, Holotropic Breathwork, Turtle Breathing etc. They focus primarily on getting as much oxygen inside you and stimulate different glands that synthesizes substances (such as hormones) for release into the bloodstream.
The pineal gland produces serotonin and melatonin. DMT is structurally similar to serotonin and melatonin, which are both known to play an important role in regulating sleep, so it's reasonable to assume DMT would have an effect on sleep regulation too. Serotonin does a lot in the brain, and DMT can affect some of the same receptors in the brain as serotonin.
Could it be that DMT is what causes you to dream and the more DMT you have the more lucid and vivid dreams?
So if you wish to have lucid dreams or astral project I suggest you to research breathing techniques, find a one you like and do it before bed.