Count as you breathe.
Breathe in 1-2-3-4.
Breathe out 1-2-3-4.
If the doctor's good, they'll keep you talking and talk to you for further distraction
walking you through each step they take.
Most of the time, certain tests don't take much longer than 30 seconds and afterwards they'll leave you alone so you can recover if you need it.
Talk to them beforehand so they know you're anxious
and see what they can do to help you get through it.
Knowing options are always open to you if you need them can help put you at ease.