Treatment of Supine Hypertension in Autonomic Failure (CPAP)

This study is testing whether CPAP (a breathing machine commonly used for sleep apnea) can reduce dangerously high blood pressure that some people with autonomic failure — a nerve condition that disrupts automatic body functions — experience when lying flat on their back. **You may be eligible if...** - You have been diagnosed with autonomic failure - You have high blood pressure when lying on your back (supine hypertension) - You are willing to participate regardless of race or background **You may NOT be eligible if...** - You are a medical student - You are pregnant - You have heart failure, serious coronary artery disease, liver problems, or a history of stroke or heart attack Talk to your doctor to see if this trial is right for you.