Hi, I was just wondering if it's possible to do Circular Breathing?

ie. breathing in through your nose and blowing out through your mouth at the same time, a girl at my band said that it is possible, and I wanted to know if this is true, and if so, how, as this would be helpful to wind instrument players for particulaly long slurred passages.
Please post if you know anything about this.
Thanx
Meg_lili