Hi katw, and thanks for your post and question - it's a good one! Generally speaking, the signs and symptoms of carbon dioxide (CO2) retention, can vary from patient to patient. These can range from feeling tired and confused, to dizziness and experiencing an increased breathing rate. However, these few signs I've mentioned should not be an indication to any of our readers that these are indicative of a rising CO2 for any of us. This truly is something to be discussed with one's own doctor, especially if there is an individual concern.
If your doctor advised you to maintain the oxygen saturation level between 90%-95%, that is what you should be monitoring. The pulse oximeter, as you well know, will help you to do this.
There is a type of chronic obstructive pulmonary disease (COPD), in which the patient chronically retains CO2. This is somewhat different than the question you posed here. To be thorough, though, I did want to mention it. Is this what your concern is, katw? Has your doctor spoken to you about this type of COPD in your particular case?
Leon (site moderator COPD.net)