Adrenaline, a naturally occurring hormone that raises blood pressure, is used as part of the standard cardiopulmonary resuscitation (CPR) protocol. Adrenaline is usually given through an intravenous catheter, a small tube that is put into a vein. When an intravenous catheter is not available, experts have suggested putting large doses of adrenaline into the bronchial tubes (airways). You do this by putting it through the breathing tube put into a patient's airways during CPR. It has been assumed that adrenaline will be rapidly absorbed from the airways into the bloodstream, but no effects have yet been demonstrated in adult humans.