My primary concern is postop obstruction of his airway. If he has already been diagnosed with sleep apnea and is not treated, we KNOW that he obstructs his airway and drop his sats in his sleep at baseline. So in a perfect world he's already desatting overnight. Now we are going to give him an anesthetic and narcotic pain medicines which will further alter his CO2 response curve and send him home unmonitored. So now instead of waking up when he desats a little and starting to breath again, he'll desat much further because of the narcotics in his system. How much further? Don't know. Don't want to know.
If he was compliant with his CPAP and would wear it overnight postop, the risk of postop respiratory failure is likely exceedingly low. But if he doesn't, it's much higher.
The issues of chronic treatment and pulmonary hypertension and this and that are all relevant, but less important to me than him dropping dead from an obstructed airway in his sleep.