If the breath gets very, very subtle, or if it disappears entirely, instead of taking a deep breath, shift your attention away from the breath to a pleasant sensation. This is the key thing. You notice the breath until you arrive at and sustain access concentration, and then you let go of the breath and shift your attention to a pleasant sensation, preferably a pleasant physical sensation. There is not much point in trying to notice the breath that has gotten extremely subtle or has disappeared completely—there’s nothing left to notice.
