Inhaled Treprostinil (Tyvaso Nebulizer) For COPD Patients With Hypoxemia

Participants will receive inhaled Treprostinil (Tyvaso nebulizer), 6 µg per breath, administered four times daily for 4 weeks. The starting dose will be 3 breaths per session. The dose will increase by 1 breath per session each week, as tolerated, to a target of 6 breaths per session by week 4. If adverse effects occur, participants will remain at the highest tolerated dose. The drug will be administered using the Tyvaso inhalation system provided by United Therapeutics. No changes to baseline COPD maintenance medications are allowed during the treatment period. Participants will be monitored for safety throughout the study.