Speckle Plethysmography Pulse Transit Time as a Marker of Blood Pressure Changes

Background: Blood pressure is one of the key markers of cardiovascular health. High blood pressure, also called hypertension, can increase the risk of heart disease or stroke. Monitoring a person s blood pressure continuously over a 24-hour period at home is the best way to diagnose hypertension, but the equipment currently used to do it is cumbersome. This natural history study will test a new technique for monitoring blood pressure continuously over time. Objective: To test a new technique (speckle plethysmography) for measuring blood pressure in healthy adults. Eligibility: Healthy people aged 18 years and older. Design: Participants will come to the clinic a minimum of 2 times. The screening visit will last up to 2 hours. Participants will have a physical exam. Their vital signs will be taken. The clinical visit will last up to 1 hour. Participants will recline in a chair. Sensors to measure the activity of the heart will be placed on their chest. Different sensors will be placed on two fingers and one big toe. A device to measure blood pressure will be placed on one arm. While wearing the sensors, participants will undergo 3 tests: They will be asked to breathe slowly for 2 minutes. They will be asked to solve a math problem. They will immerse one hand or foot into an ice bath for up to 2 minutes. Each test will be followed by a 5-minute recovery period. Participants may elect to return for up to 3 more visits during the following week.