(1)
Facts About The Human Body
31st August 2017

(15)
What Is Central Blood Pressure?

WHAT IS CENTRAL BLOOD PRESSURE?

WHAT IS Central Blood Pressure?
It’s the pressure in the Aorta which is the main artery that your heart pumps blood into. The name “Central Blood Pressure” medically refers to the blood pressure in the Aortic Artery. Unfortunately, measuring blood pressure in the aortic artery cannot be measured by simply putting a cuff around the arm, more is explained in this section.
I’ve recapped below how blood pressure is measured using the cuff, a stethoscope and sphygmomanometer . Also explaining more about the brachial artery in the upper arm, and arteries that make up the arterial tree.
The Cuff is used to take blood pressure, it has an inflatable rubber sac that goes around the top of either arm to measure blood pressure. The results can be measured on an electronic blood pressure machine or with a stethoscope, the Doctor uses a hand-held pump to tighten the cuff, the doctor then listens to the flow of blood on a stethoscope, the measurements of blood pressure are displayed on a sphygmomanometer.
 

What is a sphygmomanometer?

parallax background
 
What is a sphygmomanometer? It’s an instrument for measuring blood pressure, the cuff is connected to a column of mercury with a graduated scale, this allows the Doctor to measure the systolic and diastolic pressure, ideally between 90/60mmhg & 120/80mmhg.

The Brachial Artery


The Brachial Artery is in the upper part of either arm, it’s connected to the Axillary Artery providing oxygenated blood to both arms. The Brachial Artery continues down the arm to the elbow joint, medically known as the Cubital Fossa.
The cuff, mentioned above, is wrapped around the upper arm, 1cm above the elbow. When a doctor or health professional is measuring blood pressure using a sphygmomanometer, they use their Stethoscope to listen to the pulse in the area 1cm above the elbow, this provides the systolic and diastolic blood pressure.


The Arterial Tree


The Arterial Tree refers to all the arteries in a human body, the brachial and axillary arteries are just two of the many arteries that are in the human body. You can read more in the section on The Circulation System.



BLOOD PRESSURE is traditionally measured with a cuff and sphygmomanometer over the brachial artery, and is accepted as an important predictor of future cardiovascular risk. However, systolic pressure varies throughout the arterial tree, such that aortic (central) systolic pressure which may be higher or lower than corresponding brachial systolic & diastolic readings, although this difference is highly variable between individuals. Emerging evidence now suggests that central pressure is better related to future cardiovascular events than the brachial pressure.
parallax background
Moreover, anti-hypertensive drugs can exert differential effects on brachial and central pressure. Therefore, basing treatment decisions on central, rather than brachial pressure, is likely to have important implications for the future diagnosis and management of hypertension. Such a shift in pattern, requires further direct evidence that selectively targeting central pressure, brings added benefit, over and above that already provided by brachial artery pressure.
CENTRAL BLOOD PRESSURE in the aortic artery gives Doctors valuable information compared with measuring blood pressure in the upper arm. Apart from being closer to the heart and brain, the blood pressure in the aortic artery can differ from measuring blood pressure using a cuff on the arm. It is possible that Doctors may find that the systolic pressure in the aortic artery is higher than the pressure measured with a cuff around the arm. This technology may highlight that treatment is required and may have been missed by a measurement taken with a cuff.



MEASURING CENTRAL BLOOD PRESSURE is normally carried out while the patient is awake, albeit sedated. The procedure is carried out by inserting a catheter , which is a long thin tube, into either the neck, wrist or groin, the catheter is then guided by the cardiologist or surgeon who watch progress on monitor screens as the catheter moves from the groin/neck/wrist to the aortic artery where the central aortic systolic pressure can be measured. Although this gives Doctors valuable information, the procedure is invasive and may lead to possible complications.
parallax background
The procedure using a catheter as described above is also used to look inside the right or left ventricle of the heart.
This procedure can also identify if the arteries have narrowed or any partial blockages, examine the valves in the heart, measure oxygen levels in the heart and even take a sample of tissue for a biopsy. A catheter is also used for patients who are admitted for Angioplasty, this procedure is described in detail in the section (30) on "Your Heart & Arteries".
 
SCIENTISTS have recently found a non-invasive way to measure the central aortic systolic pressure. This new technology takes pulse wave measurements which, combined with systolic and diastolic readings from the conventual cuff method, can compute central aortic systolic pressure readings, giving Doctors valuable information enabling them to make informed decisions regarding treatment.



CENTRAL AORTIC BLOOD PRESSURE AND PULSE WAVE VELOCITY (Note 01)
Technological advances in non-invasive measurement of vascular structure and function have generated considerable interest in the use of central aortic blood pressure and pulse wave velocity as predictors of cardiovascular risk. Recent articles detail the technical aspects of measurement, and predictive value of these measures in the general population and in chronic kidney disease. These devices allow measurement of large artery stiffness represented by pulse wave velocity, and measures of central pressure including the augmentation index, central systolic pressure and central pulse pressure which measures the difference between the diastolic and systolic blood pressure.
The central blood pressure equipment requires modest training and time, and can be implemented in a clinical setting. During a cross-sectional analysis of patients with Chronic Kidney Disease from the Chronic Renal Insufficiency Cohort Study (CRIC) Study, it was reported that central pulse pressures are positively and independently compared with increasing brachial pulse pressure, older age, female sex, and the presence of diabetes mellitus .
These measures independently predict risk of cardiovascular disease in the general population, though the measure of systemic arterial stiffness added predictive value to conventional measures of blood pressure. Recently, measures of arterial stiffness estimated on home blood pressure readings have also been shown to have a future significance.
The role of centrally measured blood pressure in treating high blood pressure is less well defined. In a study of participants enrolled in the Anglo-Scandinavian Cardiac Outcomes Trial, there was no difference in brachial systolic BPs between treatment groups. However, compared to atenolol (which is a Beta Blocker that affects the heart and circulation) therapy, Amlodipine, (a calcium channel blocker that dilates (widens) blood vessels) therapy, resulted in significantly lower central aortic systolic pressure and central aortic pulse pressure. Additionally, elevated central pulse pressure was associated with increased risk for the composite outcome that included cardiovascular events and kidney failure.
Other studies have shown that ACE (Angiotensin-converting-enzyme inhibitors) and ARB (Angiotensin II receptor blockers) based therapy, may be more effective in lowering central aortic pressure than other antihypertensive drug therapies.

Click the button below to explore more sections on the website