My husband returned home from the hospital last Thursday after being admitted on Monday with a CO2 level of 115.  This was our first experience with a flare up or exacerbation.  We still haven't gotten a good answer on WHY he was retaining CO2.  He is a big sweets eater and we were told that simple sugars can contribute to CO2 retention.  We're also wondering if he has been using too high of a liter flow for his O2.  Any ideas on CO2 retention and your experiences would be greatly appreciated!  Thank you.