One thing I find fascinating is that when you hold your breath long enough and your body is forcing you to breath, your lungs still hold plenty of oxygen. If y

One thing I find fascinating is that when you hold your breath long enough and your body is forcing you to breath, your lungs still hold plenty of oxygen. If you exhaled into an empty bag, then inhaled that air back into your lungs, that reflex would be quelled for awhile. Of course after each cycle the O2 content would drop an CO2 would rise and the period of each cycle would get shorter.