carbondioxcide is high

I am not sure if this is spelled right. My blood work all came back good except this is high. Has anyone had this and have any ideal what to make out of it. I know I have chf is this maybe what is causing this. My doctor said it can cause sleep apnea. I did have it and asumed it was gone. My mom died in her sleep at 58 no cause of death. Just died in her sleep. She was 210 pounds so she really wasnt that over weight. I just dont know what to make of this. Thanks for your help Barb