Was recently prescribed a Nippy mask by Harefield Hospital after a sleep study test which found that I retain CO2 at night, hence the insomnia. After struggling with the instructions and deciding which bit went where, I finally put it on Thursday night. Only managed a couple of hours before I had to take it off. I didn't feel at all sleepy. The next day I found myself hyperventilating. Took me nearly 3 hours to get ready for work.. I must be doing something wrong. Would be grateful for any suggestion.