I think there May be some confusion if you are talking about a pulse oximeter, a small apparatus that you place on the tip end of one's finger, preferably the ring or middle finger on the left hand. Those devices measure O2 levels not CO2. The reading to the small window on the left measures SpO2, on the right is PRbpm (Pulse Rate-beats per minute0). The SpO2 level should remain 88% and above. The only way to measure the CO2 level is through lab work. Maybe this is why you have made so many trips to the ER and ended up in the ICU. Please call the physicians office tomorrow first thing and see if there is a nurse, or even the PCP to instruct you on the readings of the pulse oximeters.