Supine hypertension is a common problem that affects at least 50% of patients with primary autonomic failure. Supine hypertension can be severe and complicates the treatment of orthostatic hypotension. Drugs used for the treatment of orthostatic hypotension (eg, fludrocortisone and pressor agents), worsen supine hypertension. High blood pressure may also cause target organ damage in this group of patients. The pathophysiologic mechanisms causing supine hypertension in patients with autonomic failure have not been defined.
This study will test the hypothesis that continuous positive airway pressure (CPAP) has an acute lowering-BP effect in autonomic failure patients with supine hypertension. CPAP is a widely-used treatment for sleep-related breathing disorders including sleep apnea, that uses mild air pressure to keep the breathing airways open. It involves using a CPAP machine that blows air into a tube connected to a mask placed over the nose, or nose and mouth. For these studies, a commercial CPAP device will be used to apply pressure sequentially at 0, 4, 8, 12 and 16 cm H2O for 1-20 minute each. Depending on the BP response and tolerability to CPAP, CPAP may be applied during the night using a CPAP level that was tolerable and showed a BP-lowering effect during the acute test.
