Supine Hypertension is when blood pressure is high when lying down. This study is about trying to lower it using CPAP (Continuous Positive Airway Pressure). CPAP is a machine that helps people breathe by blowing air into their nose or mouth through a mask. We want to see if CPAP can help lower blood pressure in people with Autonomic Failure, a condition where the nervous system doesn't work properly, making blood pressure hard to control. The study will use different levels of air pressure to find what works best.

• The study involves testing the CPAP machine with different pressures for short periods (1-20 min).
• If CPAP helps, it might be used at night.
• Participants must have autonomic failure and supine hypertension.

People who are pregnant, in medical school, or have certain health issues like heart failure, asthma, or a history of stroke can't participate. This study checks if CPAP can be a new treatment option for managing high blood pressure when lying down.