In a national sample of Veterans, SDB was a significant risk factor for opioid-related toxicity and overdose; and the presence of CSA combined with chronic prescription opioid use compounded the mortality risk. There are only limited and partially effective therapies for this sleep disorder and the exact mechanisms by which opioids produce SDB in adults remain unclear, and varied and conflicting ventilatory control mechanisms have been suggested. This proposal will investigate whether alternative therapies can be developed by modulating specific physiologic mechanisms of ventilatory control. Specifically, the investigators will study effects of chronic oral prescription opioids on chemoresponsiveness and cerebrovascular responsiveness (CVR) (Aim 1); and whether interventions with sustained hyperoxia (Aim 2) and acetazolamide (Aim 3) will reduce the apneic threshold (AT) to alleviate breathing instability and SDB in chronic prescription opioid-associated SDB. The proposed aims will also allow us to delineate key mechanisms of breathing instability with opioid and without opioid use. The information garnered from the proposed experiments will drive development of novel personalized therapies to reduce SDB associated with chronic opioids in Veterans and, ultimately, will positively impact their long-term health and well-being.