It is when when you have to. And it isn't like being underwater. You pretty much close your eyes and go to a different place. And like I said. Pills help a lot.

And I had practiced (sitting at my desk) once I knew what had to be done and really struggled. No doubt, once they said I could breathe I spent a few minutes gasping for air.

But I have been shooting hoops for about 45 minutes everyday in the driveway for months. So my cardio is way better than the first time I had to do this. This time will be a picnic. The nice thing about radiation is they let you pick what music you want. Being the horrible person I am I use it as a way to introduce the radiation techs to new music.

90 seconds is uncommon for complete novices, but most people can get to 2-3 minutes within a day or two of training. It's almost entirely psychological up to that point; blood oxygen levels barely drop for the first few minutes you hold your breath while at rest. You just need to learn what the sensations are, that they are normal, that you aren't at risk (assuming you've done some basic amount of safety education), and to relax into it.