They tried this on with me every visit to an ophthalmologist, white coat syndrome had my blood gushing out of every orifice according to their test(s). They got me to lie down for 20 minutes it somehow went higher. The looks on their faces, how can you still be conscious? can you see through the red mist? I got out of bed and did 3 star jumps (no lie), nope I'm good. I was feeling extra saucy that day. They then insisted on a wheelchair, which I took because it looked like fun, knowing that every little thing was going to be on my bill.
I then actually paid attention to how they applied the cuff, and as someone who has been on the administering side an age ago realised that some staff do not get much training.
Not all cuff sizes are the same, even if adjustable. Turns out they had mixed up the kids cuffs with those used for adults resulting in see-saw results.
side note: my lady ophthalmologist was a smoke show, hot dam, Dr Butternut.