Hi Hairspray

It sounds like you may be talking about being tested for sleep apnoea. If so, you will need to take the system off for that. But it is not a big deal - I just went in without my system and with a cap on. Once the sensors are positioned, you can put on a bandana if you like. No one needs to see you bald except the technician, but I'm sure they see plenty of guys who wear hairpieces, and they know to be discreet.

Obviously if you are having surgery on your head, you will also need to take your unit off. They will give you a paper surgical cap to wear. For other kinds of surgery, there is no reason why you need to take your system off or even mention it. Often the instructions say 'remove all jewellery, dentures and hairpieces', but I have been told by medics that you don't have to take that literally. If you are having your ingrown toe treated they don't need to know about your hair system!

There is no issue with airports either, in the US or elsewhere. There was some debate about whether the new hitech scanners could pick up the fact that someone is wearing a system. I think the consensus was no, unless you use clips to attach. But even if they do, the worst that could happen is that you get asked to go into a private sideroom and get your head patted. They are no way going to require you to remove it or mention it in earshot of other passengers.