Breath holds in box breathing or Wim Hof breathing typically involve exhaling all air and holding for 15-60 seconds after 25-30 cycles of deep inhales and exhales.

“Well, that's a whole business into itself. But for sake of meditation, the key thing to understand is that if you are going to do a complicated breathing practice, it will, by design, by necessity, shift much of your attention to the breathing practice, especially if it's not cyclic, if it's not inhales follow exhales.”