Hello Bettina,
Jay had SRS radiation and had to wear that mask too. He has been a tough guy going through radiation, chemo, and the effects from everything. He rarely complains, but towards the end of the radiation he didn't want to wear the mask, it was getting tighter because of facial swelling from the steroids.
My suggestion would be for him to get some medication to mildly sedate him, like xanax or ativan. I saw a lot of patients being brought in sedated. He will be nervous enough going the first time so I would suggest he takes something before to relax him until he knows how he will react. I think breathing techniques and trying to take his mind somewhere else will help, but if he is nervous already I would suggest medication.
I wish your brother and you the best.
Take care,
Lori