I didn't. I don't know how. I just recognized the symptoms.

To measure Co2, you can purchase an oxymeter at CVS, Walgreens, most any pharmacy. I was told, seeing my husband has COPD, that his "safe Zone" is 87 - 100. Once he starts talking strange, getting loopy, somehow I managed to get him to agree to get to the hospital so I would drive him to emergency room. He'd start nodding out on the ride so they would take him immediately. As I've said earlier in a separate message, it's been like 12+ times this has happened. It was not because he took opiates or xanax because he was on such a low dose after the first episode happened. Being an addict had been tough on him but I'm glad our local hospital is a 5 min drive vs havin to drive to Boston. Age can have a lot to do with it especially the lost weight as well as to why he was hypercapniac. His blood tests would come up showing zero opiates and zero benzos in his system but he still went unresponsive. Very scary. Sorry I went down a rabbit hole "heart4wi", but do buy an oxymeter. You'll feel more comfortable in making a decision whether a trip to the ER is necessary or not. Blessings to all. Betsc