A 38-Year-Old Man With Well Treated OSA on CPAP With Persistent Nocturnal Hypoxemia.

CASE PRESENTATION: A 38-year-old male with a prior diagnosis of severe OSA (apnea-hypopnea index [AHI] 99/h) presented for transfer of care. He was successfully titrated to CPAP of 10 cm H2 O at an outside laboratory and was compliant with therapy with residual AHI 1.9/h. On presentation, he was polycythemic, with negative evaluation for primary polycythemia, and evaluation for hypoxemia was initiated.