Suhas,
"At a very advanced stage, one acquires so much control that body functions receive prana directly as closed-loop cycles of prana start running along the chakra path. ONLY THEN, one can stop breathing of air as it becomes redundant. "
It can happen spontaneously through those more forceful methods, but is also something that is possible as a natural by product of meditation. Without practicing any pranayam whatsoever, with a one-pointed stream of uninterrupted mindfulness, one’s awareness naturally starts turning inwards onto itself. As this happens, the quality of one’s breath goes through a series of changes. One’s rhythm of breathing naturally becomes slower and slower, subtler and subtler, until it almost disappears. In most cases, it is not really the case that the breath has disappeared, it has simply become so subtle that it may be very difficult to detect. There is a depth beyond this, when the breath is actually suspended, but it is again not a matter of control - it is something that happens as a consequence of a certain samadhi.
