Very unlikely. Here's a back of the envelope calculation: The human energy requirement per day is about 9MJ. This corresponds to about 500g sugar (or starch), which releases around 750g CO2. Metabolic activity is reduced at night, so 250g CO2 is the upper limit for a full night's sleep. At typical temperature and pressure, this is < 0.14 m^2 of CO2. Assuming a very small (20 m^3) and hermetically sealed bedroom, you'll end up with a concentration of 0.7%, or less. Serious physiological studies (with divers and submariners) show that CO2 has a measurable effect starting at about 1% concentration and only becomes pronounced at 3% or so. This is consistent with the fact that exhaled air contains about 4% CO2 during normal breathing and can go much higher (>10%) during breath holds. In summary, sleeping in a stuffy room might give you respiratory problems, but no improved CO2 tolerance.