[Encannavalf]

This is what AB says in his book:

In deep jhana we can experience the breath disappearing altogether with no danger to life.

During my teacher Ajahn Chah's long sickness, he would often stop breathing.On one such occasion the new nurse on duty became alarmed. He knew that Ajahn Chah must die one day, but he didn't want it to happen on his shift! The attendant monks on duty that night assured him that Ajahn Chah had done the same many times before and it was just a sign of deep meditation.
After taking a blood sample the worried nurse has discovered that the oxygon level in his blood was a constant even though he stopped breathing altogether. Apparently during deep meditation the metabolism is so slowed down that the body does not need to breathe.

Quote from page 110 : Mindfulness, bliss and beyond