I read something very interesting once, it's not really about how well you can hold your breath, if you have serious lung injury such as emphysema you can't exhale well, therefore will not be able to draw deep breaths. To see what it's like if you have empthysema, inhale, then without exhaling, inhale again, and again, and again (do not exhale between inhales)... you end up oxygen deprived because you can't take anymore in, and once what's inside is depleted, you are out of air, but can't pull in more. You can only take gasping, short, weak breaths that don't satisfy the lungs when you have emphysema. If you COULD take the three deep breaths before starting the breath holding experiment, you're in good shape. It's a lot of the reason why doctor's and hospitals use those tube/ball thingies to test breathing capacity (can you inhale strong enough to get that ball to rise in the tube?) and also to help patients recovering from surgery, pneumonia and other lung problems expand their lungs and help them heal.