Treprostinil Therapy For Patients With Interstitial Lung Disease And Severe Pulmonary Arterial Hypertension

Inclusion Criteria: Eligible subjects must have IPF and severe pulmonary arterial hypertension (PAH) documented on standard of care right-heart catheterization (RHC) and planned to receive therapy with treprostinil as recommended by the treating physician. 1. All subjects must have high resolution CT scan (HRCT) diagnostic of IPF (performed as part of standard of care evaluation) or if available, biopsy proven histological usual interstitial pneumonia (UIP). 2. Severe pulmonary arterial hypertension defined as a resting mean pulmonary artery pressure (mPAP) \> 35 mm Hg; AND pulmonary vascular resistance (PVR) \> 3 woods-units; AND pulmonary capillary wedge pressure (PCWP) \< 18 mm Hg by right-heart catheterization (RHC) performed as part of standard of care evaluation. 3. All subjects must be planned to receive treprostinil therapy as recommended by their treating physician. Exclusion Criteria: 1. Acute or chronic impairment other than dyspnea (e.g. angina pectoris, intermittent claudication) limiting the ability to perform standard of care six-minute walk tests (6MWT). 2. Six-minute walk distance (6MWD) \< 50 meters at screening or baseline standard of care evaluations 3. Standard of care pulmonary function test (PFT) showing forced expiratory volume in one second (FEV1)/ forced vital capacity (FVC) ratio \< 0.65 4. Standard of care pulmonary function test (PFT) showing a residual volume \>120% predicted 5. Standard of care high-resolution chest computed tomography (HRCT) showing emphysema extent \> 30% 6. Any investigational therapy as part of a clinical trial for any indication with 30 days before screening 7. Change in dose of treatment for IPF - investigational agent (gamma interferon-1b, pirfenidone, etanercept, and any other investigational agent intended to treat IPF), corticosteroids, or cytotoxic agents, within 30 days before screening. That is, subjects can be on any of these agents provided the dose is stable for at least 30 days prior to enrollment. 8. Current treatment for pulmonary hypertension with other prostaglandins (epoprostenol or iloprost) 9. Change in dose of treatment for PAH - (bosentan, sitaxsentan, ambrisentan, tadalafil, sildenafil, vardenafil, calcium channel blockers, nitrates, digitalis), within 30 days before screening. That is, subjects can be on any of these agents provided the dose is stable for at least 30 days prior to enrollment 10. Pulmonary rehabilitation initiated within 30 days of baseline.