24-hour Blood Pressure Measurements and Ischemic Conditioning

Study Overview
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Brief Summary
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To determine if 24-hr ambulatory blood pressure monitoring effects endothelial function, we will measure flow-mediated dilation before and after the blood pressure monitoring (ischemia conditioning).

Detailed Description
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Reestablishing blood flow (reperfusion) to organs that had their blood supply restricted (ischemia) can cause damage to the vasculature via injury and tissue death resulting in endothelial dysfunction. This ischemia-reperfusion (blood flow occlusion and resupply) triggered injury can be reduced or prevented by preceding brief periods of ischemia called preconditioning. Properly-performed preconditioning can exert a powerful protection against a subsequent sustained period of ischemia in a variety of organs in the body including the heart, kidney, and skeletal muscle. Preconditioning protocol involves repeated brief inflation and deflation of a blood pressure cuff. In many of human cardiovascular research studies, it is common to measure endothelial function and ambulatory (24-hour) blood pressure. The ambulatory blood pressure device takes repeated blood pressure readings every 15-30 minutes during the daytime and 30-60 minutes at night. It is possible that repeated bouts of inflation/deflation of the blood pressure cuff could induce preconditioning effects and influence endothelial function. Therefore, in the proposed study we aim to address this hypothesis.

Official Title
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24-hour Blood Pressure Measurements and Ischemic Conditioning

Conditions
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Blood Pressure

Intervention / Treatment
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* Device: Ambulatory (24-hour) Blood Pressure


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adults aged between 30 to 60 years old. Exclusion Criteria: Exclusion from the study may be due to: i) pregnancy (by asking the subjects when the last time she had menstruation; we do have simple testing kits available if a subject is unsure about her status); ii) a recent illness, recent surgery, or any medical intervention in the 48 hours before any of the study days; iii) personal history of diabetes (fasting blood glucose > 126 mg/dL), heart disease, or other cardiovascular problems.

Ages Eligible for Study
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Minimum Age: 30 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Ambulatory (24-hour) Blood Pressure<br> | Device: Ambulatory (24-hour) Blood Pressure<br>* Unlike casual blood pressure measurements, 24-hour ambulatory blood pressure monitoring provides an insight into blood pressure changes in everyday life and an estimate of the overall blood pressure load exerted on the cardiovascular system over 24 hours. Blood pressure recordings over a 24-hour period of normal daily activity will be made using a noninvasive ambulatory monitor (Spacelabs, Redlands, WA). The ambulatory system will be calibrated against a mercury sphygmomanometer, and the cuff will be programmed to inflate automatically every 15 min from 6 AM to 11 PM and every 20 min between 11 PM and 6 AM. For each individual subject, the nighttime period will be defined as the time when the subject goes to bed at night until rising in the morning. Daytime will be defined as the remainder of the 24-hour period. Daytime and nighttime states will be monitored by an Actiwatch (Mini-MItter, Bend, OR), a watch-like device placed on the wrist that measures gross motor activity.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change From Baseline in Flow Mediated Dilation After 24 Hour Ischemic Conditioning With Blood Pressure Cuff | Flow-mediated dilatation (FMD) is a common and non-invasive method to assess vascular endothelial function by measuring the Brachial artery's responsiveness (diameter percent increase) following a brief period of occlusion. | Baseline, Post 24 hour conditioning |