Thanks for your replies.
I wasn't clear about what I was asking. I know I can get my CPAP through security (I fly with it about 150K/year). I do not have to use it on board--I can make do without it for a night. But it is a very fragile piece of equipment and I cannot check it. Therefore, I was trying to find out if the CPAP will be counted as one of the two permitted carryons (which would require me to put my computer bag inside my rollerboard) or whether it is allowed as an extra carryon (permitting me to take the rollerboard, computer bag AND the CPAP), as is true within the US.
I appreciate the advice to ask KLM directly. I'll send them an email.