Wednesday, July 17, 2013

Blood pressure: why you need to know.


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William Harvey was born in Kent, England on April 1st 1578 and received his Medical Degree from the University of Padua, Italy in 1602. After his return to England he became Fellow of the College of Physicians and physician to St. Bartholomew's Hospital - my old Alma Mater. In 1618, Harvey was appointed physician extraordinary to James I. Harvey's famous Book, commonly referred to as "De Motu Cordis" was published in Latin at Frankfurt in 1628, when Harvey was 50 years old. The first English translation did not appear until two decades later. In Chapter 13, Harvey summarized the substance of his findings: "It has been shown by reason and experiment that blood by the beat of the ventricles flows through the lungs and heart and is pumped to the whole body. There it passes through pores in the flesh into the veins through which it returns from the periphery everywhere to the centre, from the smaller veins into the larger ones, finally coming to the vena cava and right atrium..... It must therefore be concluded that the blood in the animal body moves around in a circle continuously and that the action or function of the heart is to accomplish this by pumping. This is only reason for the motion and beat of the heart."
Thus, for over 380 years we have known that blood circulates around our bodies as a direct consequence of the pumping action of the heart - and of necessity, the blood within those blood vessels must be under pressure: and the challenge since then has been how best to measure that pressure and relate it to the pressure-related diseases that can affect the heart and those blood vessels which transport the blood to the organs which they supply .. the kidneys, the brain, the eyes and so on. And we had to wait for 2 centuries for one Siegfried Karl Ritter von Basch to invent the first primitive blood pressure machine - or sphygmomanometer - in 1881 and another 15 years for Scipione to modify it into the mercury manometer that was to remain the mainstream tool to indirectly measure the pressure of the blood within the blood vessels. It wasn’t until the latter part of the 20th century when the mercury manometer was slowly but surely replaced by more modern electronic equipment. But it wasn’t just the electronics that made Von Basc’s original concept obsolescent, his device was replaced mainly because the mercury within them is known to be extremely toxic to we humans  and disposal of those instruments was considered a health hazard!
A blood pressure machine works by occluding the flow of blood in the upper arm with the aid of an inflatable rubber cuff. The cuff is then slowly deflated and 2 numbers are recorded which relate to the pressure within the artery when the blood is pumped out of the heart, and the pressure within the artery when the heart is relaxed - in medical terms these are called the systolic pressure and the diastolic pressure. When I started medicine, the healthy reading for an adult was 140/80 but over the years this dropped to 120/80, but just when we were getting used to those numbers, the most recent advice is that the normal figure should be .... 140/80 again! Which can be interpreted as either what’s old is new again, or more correctly that scientists are constantly reviewing the information they have and then giving the most up to date and informed advice on how to best use that information in the clinical setting.
Knowing what the normal pressure is has allowed us to look at very large populations of people and realize that as blood pressure goes up so does the rate of heart disease, the risk of having a stroke and of suffering more serious kidney damage. The problem is that high blood pressure does not have any symptoms and the only way you can discover if your blood pressure is up is to actually measure it! And why do people get blood pressure? Well in about 90% of cases we have absolutely no idea why! The good news is that we have developed many good and effective medications that can control it and bring it down to the normal range - but even then it is really important that the blood pressure is measured long term to make sure that it remains normal.
Despite having more user friendly electronic blood pressure machines,  the challenge has always been to interpret the results that these machines give us. For instance, some people with normal blood pressure - and this is thought to be about 20% of the population - when they go to a Doctors surgery actually get a little agitated and their blood pressure goes up: this is known as the white coat effect, and in reality these people should not be treated for blood pressure problems, but rather for a case of mild “Social anxiety disorder” brought on by being in a medical environment. At the other end of the spectrum are those who do have higher blood pressure yet feel reassured by being in a Doctors surgery and their blood pressures actually fall a little bit - and this is known as the reverse white coat effect.
Added to this confusion is the challenge of which blood pressure measurements do we determine to be useful - office testing, home testing or random testing - because if treatment is based on unreliable blood pressure results, this can lead to unnecessary long term - and in many cases expensive - medications which also have the potential for side effects.
So what is the correct way to get an accurate measure of blood pressure? Resting blood pressure has long been the gold standard measurement - this is to be taken on a patient who has been lying down for a few minutes in comfortable surroundings, and then the pressure recorded using a blood pressure cuff on the upper arm: and most professionals will repeat the measurement a second time after a few more minutes to confirm the recordings are accurate. This method of recording blood pressure has now been backed up by Ambulatory  blood pressure monitoring that allows the specialist to see how a persons blood pressure reacts over a 24 hour period. Of course, when you undergo physical exertion, your blood pressure will go up - and this is a very normal response to  physical activities - but it should come down afterwards in someone who has normal blood pressure, and having access to information gleaned over 24 hours allows the experts to determine what is normal and what is probably not normal.
Where ambulatory blood pressure monitoring is not easily available, I encourage patients to perform home monitoring to back up what the Doctors are recording in their offices, as it does give instant feedback to the individual: and with the cooperation of the treating Doctor, this can also allow the patient to fine tune their medications in order to obtain tighter control.
Once high blood pressure has been confirmed, it is important to continually gather blood pressure readings both at home and at the Doctors office - so that medications can be adapted to the individual and the changing circumstances of their lives.
But having high blood pressure doesn’t always mean taking medications, each individual can have an impact by adopting lifestyle changes that can help lower their blood pressure:
Lose weight
Stop smoking
Exercise regularly
Cut down on excess salt intake
Cut down on alcohol consumption to the recommended intake
Take up meditation or yoga

These lifestyle changes will not only help lower blood pressure, they can also enhance your health and overall well being, and reduce the chances of developing other chronic health diseases too.
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3 comments:

Starting Over, Accepting Changes - Maybe said...

The good news today is that there are many medicines that can help control high blood pressure. Lifestyle changes definitely affect the condition, but sometimes it just seems to come with the genes given to you by your family.

mybabyjohn/Delores said...

I most definitely have the 'white coat syndrome' and my doctor takes my blood pressure both before and after we get down to 'business'....it's always normal after.

Mariodacatsmom said...

Excellent article again. I managed to ward off medications until i was in my high 60's. You might be interested in the good news in my blog. I've now been diagnosed as Essential Tremors instead of Parkinson's. It's been a long haul to get to this point.