Clinical Research Directory

CPAP for the Treatment of Supine Hypertension

This study aims to learn about the effects of continuous positive airway pressure (CPAP) on people with autonomic failure and high blood pressure when lying down (supine hypertension) to determine if it can be used to treat their high blood pressure during the night. CPAP (a widely used treatment for sleep apnea) involves using a machine that blows air into a tube connected to a mask covering the nose, or nose and mouth, to apply a low air pressure in the airways. The study includes 3-5 days spent in the Vanderbilt Clinical Research Center (CRC): at least one day of screening tests, followed by up to 3 study days. Subjects may be able to participate in daytime and/or overnight studies. The Daytime study consists of 2 study days: one with active CPAP and one with sham CPAP applied for up to 2 hours. The Overnight study consists of 3 study nights: one with active CPAP, one with sham CPAP, both applied for up to 9 hours and one night sleeping with the bed tilted head-up.

A Study in Subjects With Neurogenic Orthostatic Hypotension

This is a study to evaluate the effects of CST-3056 on orthostatic symptoms and signs in subjects with neurogenic orthostatic hypotension (nOH).

Effect of Midodrine vs Abdominal Compression on Cardiovascular Risk Markers in Autonomic Failure Patients

The purpose of this study is to learn more about the effects of abdominal compression and the medication midodrine, two interventions used for the treatment of orthostatic hypotension (low blood pressure on standing), on hemodynamic markers of cardiovascular risk. The study will be conducted at the Vanderbilt University Medical Center and consists of a screening and 2 testing days, one with abdominal compression and one with midodrine. The total length of the study will be about 5 days.

Natural History Study of Synucleinopathies

Synucleinopathies are a group of rare diseases associated with worsening neurological deficits and the abnormal accumulation of the protein α-synuclein in the nervous system. Onset is usually in late adulthood at age 50 or older. Usually, synucleinopathies present clinically with slowness of movement, coordination difficulties or mild cognitive impairment. Development of these features indicates that abnormal alpha-synuclein deposits have destroyed key areas of the brain involved in the control of movement or cognition. Patients with synucleinopathies and signs of CNS-deficits are frequently diagnosed with Parkinson disease (PD), dementia with Lewy bodies (DLB) or multiple system atrophy (MSA). However, accumulation of alpha-synuclein and death of nerve cells can also begin outside the brain in the autonomic nerves. In such cases, syncucleinopathies present first with symptoms of autonomic impairment (unexplained constipation, urinary difficulties, and sexual dysfunction). In rare cases, hypotension on standing (a disorder known as orthostatic hypotension) may be the only clinical finding. This "pre-motor" autonomic stage suggests that the disease process may not yet have spread to the brain. After a variable period of time, but usually within 5-years, most patients with abnormally low blood pressure on standing develop cognitive or motor abnormalities. This stepwise evolution indicates that the disease spreads from the body to the brain. Another indication of this spread is that acting out dreams (i.e., REM sleep behavior disorder, RBD) a problem that occurs when the lower part of the brain is affected, may also be the first noticeable sign of Parkinson disease. The purpose of this study is to document the clinical features and biological markers of patients with synucleinopathies and better understand how these disorders evolve over time. The study will involve following patients diagnosed with a synucleinopathy (PD/DLB and MSA) and those believed to be in the "pre-motor" stage (with isolated autonomic impairment and/or RBD). Through a careful series of follow-up visits to participating Centers, we will focus on finding biological clues that predict which patients will develop motor/cognitive problems and which ones have the resilience to keep the disease at bay preventing spread to the brain. We will also define the natural history of MSA - the most aggressive of the synucleinopathies.

Controlled CO2 Inhalation in NOH

This study focuses on neurogenic orthostatic hypotension (nOH), which is a disorder characterized by an abnormal drop in blood pressure (BP) within 3-minutes of standing. Patients with nOH experience debilitating symptoms including light-headedness, falls, and fainting. Patients often struggle with day-to-day tasks that require standing, with a reduced quality-of-life. Current therapies for nOH have limited effectiveness and unwanted side effects. Our lab has found that raising blood CO2 levels (hypercapnia) in the lab increases BP when standing in patients with nOH. We now aim to test the CarboHaler, an exogenous controlled CO2 delivery device, in this study to see if increasing CO2 levels through controlled CO2 inhalation can improve BP and reduce symptoms in patients with nOH when standing up. On the study day, participants will undergo two Head-up Tilt (HUT; upright) tests with different breathing protocols: one with and one without exogenous CO2 delivery provided by a CO2 inhalational device. We will record heart rate, blood pressure, and breathing parameters. We will also assess upright symptoms using the Vanderbilt Orthostatic Symptoms Score. Our primary outcome is the magnitude of the change in systolic BP from lying down to standing, which will be compared with and without exogenous CO2 delivery. We hypothesize that exogenous CO2 delivery provided by a CO2 inhalational device will raise CO2 enough to increase standing BP, which could reduce the debilitating symptoms experienced by patients with nOH. We hope that these data will support future clinical trials, with the long-term goal of creating a simple, low-cost treatment for increasing quality-of-life for patients with nOH.

Hypercapnia in Orthostatic Hypotension

The Autonomic (or "automatic") Nervous System (ANS) regulates internal processes, including control of heart rate and blood pressure (BP). When someone stands, and gravity tries to pull blood away from the brain, the ANS works to maintain BP and brain blood flow. Neurogenic Orthostatic Hypotension (NOH) occurs when our "fight-or-flight" part ("sympathetic") of the ANS fails. BP can drop a lot when upright, reducing blood flow and oxygen delivery to the brain, and this can cause symptoms of light-headedness, nausea, and fainting. One solution to help counter the effects of NOH may be to increase sympathetic activity by breathing higher levels of carbon dioxide. In healthy volunteers, small increases in the amount of inhaled carbon dioxide has been shown to increase BP in the upright position, and this improves symptoms! The objectives of the current study are to apply carbon dioxide in patients with NOH and healthy controls to: (a) evaluate the effects of breathing carbon dioxide on BP and brain blood flow, and (b) determine if a device that increases carbon dioxide while standing will work as a new therapy

CO2 Rebreathing in nOH: A Proof-of-Concept Pilot Study

Neurogenic orthostatic hypotension (nOH) is a chronic condition associated with increased cardiovascular risk and reduced quality of life. On standing, patients with nOH experience a large reduction in blood pressure (BP; at least ≥20/10mmHg, but often much more), which is often accompanied by debilitating symptoms and syncope. A previous study (unpublished) showed that hypercapnia significantly increases standing BP in patients with nOH. Human bodies naturally produce and exhale CO2. Rebreathe devices offer a simple, cost-effective technology to increase arterial CO2. In brief, rebreathe devices work by capturing expired CO2, which is then re-inhaled. The net effect is a transient increase in CO2. A CO2 rebreathing device may offer a novel hemodynamic therapy for patients with nOH. This is a pilot, proof-of-concept study to evaluate a CO2 rebreather to improve blood pressure and orthostatic tolerance in patients with nOH. The hypothesis is that a rebreather will increase CO2 sufficiently enough to improve BP in patients with nOH. Male and female patients (n=28) will be asked to complete two randomized 70° head-up tilt (HUT) tests breathing either room air or using a CO2 rebreather. Hemodynamics (BP, heart rate, stroke volume, brain blood flow) and orthostatic symptoms will be assessed throughout. Breath-by-breath data will include O2, CO2, respiration rate and tidal volume. The primary outcome measure will be the magnitude of the BP response (ΔBP = HUT - Supine) during Room Air vs. Hypercapnia. The primary outcome will be compared between room air and hypercapnia using a paired t-test.