Research Techniques

 

How we do the technique:
To create the change in blood flow we use a cuff, much like a blood pressure cuff to inflate around the forearm just below the elbow. To measure the blood flow we use an ultrasound. This procedure lasts for 8 minutes total: one minute before the cuff is inflated, five minutes with the cuff inflated, and two minutes after the cuff is deflated.

During this procedure you may feel some discomfort from the cuff, feeling a sensation like your hand is falling asleep. Once the procedure is completed you will be able to move your arm again to “wake up” your hand.

What we can learn:
From this technique, we can determine the percent change in diameter of the brachial artery. A higher percent change means the artery is more compliant to the change in blood flow. As we age the arteries become less compliant, or stretchy, which can lead to increases in blood pressure.

Top is a diagram showing the placement of the ultrasound probe and the occlusion cuff. Below is the blood flow recording the technique along with two ultrasound images of the brachial artery (left is during baseline, right is during deflation)

Why we do the technique:
In your body, high blood pressure is a risk factor for cardiovascular disease and is important to monitor. Blood pressure is a measure of how much the blood is pushing against the blood vessels. Your blood and blood vessels have similar properties to water running through a garden hose. The faster the water moves through the hose the higher the pressure. This technique is used to determine how smoothly the blood flows through the vessels.

How we do the technique:
We use a pressure sensitive instrument, called a tonometer, to record the pulse in an artery in your neck (carotid artery). We also record a blood pressure in your arm and leg. We take measurements between the tonometer and blood pressure cuffs to determine the distance between them. This allows us to calculate the velocity of the blood, or how long it takes the blood to move from your neck to your leg.

What we can learn:
This technique tells us how fast your blood is moving between two points in your body and how hard it is pushing against your blood vessels.

How we do the technique:

A nurse or nurse practitioner will insert a catheter into a vein in your arm. A catheter is a small flexible tube that is placed inside your vein to give access to the blood. We collect blood in special tubes that allow us to examine different hormones or cells in your blood. The amount of blood we collect is equal to a couple of tablespoons of blood, which is very small compared to a blood donation.

What we can learn:
We look at levels of hormones such as estrogen or progesterone in the blood. We also examine a type of white blood cell called a peripheral blood mononuclear cell. These cells have a nucleus which means they can express different genes and give us information about things happening in your cardiovascular system.

Why we do the technique:
The cells that line your blood vessels, endothelial cells, have important properties that help regulate blood vessel function. By examining these cells we are able to identify levels of protein expression which helps us to understand how the cells may interact with the blood vessels.

How we do the technique:
From the catheter inserted in the arm, during the blood collection, a sample of endothelial cells will be collected. To do this a registered nurse or nurse practitioner will insert a small thin wire, called a J-wire, into the catheter in your vein. The nurse practitioner will move the wire against the wall of your vessel to collect endothelial cells from the inside of your vein. You may feel a ticklish feeling or slight pressure associated with this technique. This technique will be done with two wires and then a blood draw will be taken. Our staff is trained to perform this technique and there are minimal risks associated with having this technique performed.

What we can learn:
Once the cells are collected we are able to fix them in a preservative and then use different molecular biology techniques to identify proteins in the cell.

Why we do the technique:
We use a technique called microdialysis, where we examining how the blood flow in your skin responds to different solutions. This minimally invasive technique allows us to identify how the blood vessels respond to the different solutions that are perfused. This technique requires only a small area of skin to be used, thus not affecting the entire body.

How we do the technique:
To perform this technique we clean the skin using sterile technique and numb the area using ice, to prevent discomfort when placing the needles. Once the skin is numb, we place four small needles under the top layer of skin in the upper part of the forearm. With these needles in place we are able to pass small fibers, about the size of a human hair through the needles. Once the fibers are in place the needles are removed, leaving just the fiber in the top layer of skin. Small heaters will be placed on the skin directly above the fiber to increase the local temperature of the skin and small optic fibers will be used to record the local blood flow. This technique requires about 3.5 hours to complete the protocol. This methodology allows us to examine local responses of the skin to certain drugs. Once the procedure is complete the fibers will be removed from the skin and the area will be cleaned and dressed appropriately.

These diagrams show where the fibers are placed on the forearm as well as how the membrane interacts with the small vessels in the skin.

What we can learn:
We record data on how the small vessels in your skin react to heating and different drugs. The differences in the skin blood flow response to the drugs will show how the drugs affect the small vessels.

Taking blood pressures (BP) over an extended period gives more information to assist in the diagnosis of hypertension and cardiovascular health. Ambulatory Blood Pressure is an average of blood pressures taken over a period of 24 hours.

The American Heart Association recommends if your blood pressure is normal, you should be screened during regular healthcare visits at least once every two years. If your blood pressure is high, your doctor may take several readings over time before beginning a treatment program.

 
How we do the technique:
We will give you a BP cuff which you will wear 24 hours before your study visit. BP readings are taken every 20 minutes during the day and 30 minutes at night; the cuff will inflate automatically. When the cuff starts to inflate simply relax your arm. If you are standing you can rest your arm by your side and if you are seated try to rest your arm at heart level.

During your screening visit, we will review how to wear the cuff. When wearing the monitor it is important to refrain from vigorous exercise. You can shower, however, you must remove the monitor and replace only when the arm is dry.

What we can learn:
From this technique, BP readings will be collected over 24 hours, including when you are sleeping which can give us insights into blood vessel function.