CPAP for the Treatment of Supine Hypertension

This study is testing whether CPAP — the same type of breathing device used for sleep apnea — can help lower dangerously high blood pressure that occurs when people with certain nerve disorders lie down at night. People with conditions like Parkinson's disease or multiple system atrophy often have blood pressure that drops when they stand (causing dizziness) but spikes when they lie down at night, which is hard to treat. **You may be eligible if...** - You are between 40 and 80 years old - You have autonomic failure (a nerve disorder affecting blood pressure) such as pure autonomic failure, multiple system atrophy, or Parkinson's disease - You have low blood pressure when standing up (orthostatic hypotension) - Your blood pressure is too high when lying down at night (nighttime systolic BP above 140 mmHg) **You may NOT be eligible if...** - You have had recent facial trauma or surgery, or cannot tolerate wearing a CPAP mask - You are unable to stand for at least one minute after stopping blood pressure medications - You are bedridden or cannot stand due to severe motor problems - You are a smoker or pregnant - You have unstable coronary artery disease or other serious cardiovascular or neurological conditions Talk to your doctor to see if this trial is right for you.