I have been running 20 miles a week (three hour long runs, monday, thursday, and saturday) for a long long time. Last year in my annual physical I had a venous blood carbon dioxide level of 29. This year it is 33 (upper limit of normal is 31).
Is my blood carbon dioxide level high because my system has 'learned' to tolerate high levels of carbon dioxide? Am I going to drop dead in a week or two? Does anyone know?