According to Osho, when you ask 'Who am I?' with full intensity, the breath rhythm won’t remain as before—your energy naturally shifts from breathing to the inquiry. Don’t worry about the breath; give yourself totally to whichever is alive—breath or question—until no energy is left over. Such totality itself brings the transformative result.
If you put all your energy into asking ‘Who am I?’, your breath may fade or change—just let it happen and be total.