BankAngle
Having a girlfriend doing sport science, I am constantly bombarded with facts about fitness. I suggest you find the local swimming pool and start doing some lengths a few times a week. Its one of the best ways of increasing lung capacity. Otherwise get down the gym and try out the rowing machine/treadmill! My housemate puffed out 150% of his normal lung capacity the other day at his annual fitness test!
Not saying that you're unfit by the way, just may improve this area of your fitness! GO BLOW THAT DOC AWAY!
Nick