There are several important things to know about blood pressure:
1. What is it and why should I care about it?
2. What controls it?
3. How do I measure it correctly?
4. What do I do about it?
Blood pressure is the measurement of the
force created by the pumping of the heart as it sends blood through the blood
vessels of the body. The blood
vessels which are called arteries are the pathways that send blood to all of
the organs of the body. When the
heart pumps, it pushes blood out of the heart into the arteries. This pressure when the heart contracts
is called the systolic pressure. When the heart relaxes after each
contraction, the pressure inside the heart falls and valves opened to allow
blood to go into the main pumping chamber (ventricles). This is called the diastolic blood pressure.
A typical blood pressure might be 120/80 with the 120 representing the "systolic"
pressure when the heart contracts and 80 being the "diastolic"
pressure when the heart is
relaxed. We measure these
pressures in millimeters of mercury which is abbreviated "mmHg".
We care about these numbers because high
blood pressure ("hypertension") can cause damage to blood vessels
(from big arteries such as the aorta to small arterioles that go to the very
small capillaries). High blood
pressure can and does damage all of the arteries but causes particularly
noticeable havoc to the arteries of the heart, the brain, the kidneys, and the
eyes. When blood pressure is too
high, the force of the blood causes direct damage to blood vessels and leads to
such problems as heart attack, stroke, kidney failure, blindness and actual
blood vessel rupture. So we care
about high blood pressure because we want to prevent all of these
problems. By controlling blood
pressure along with fixing other risk factors such as high cholesterol, excess
weight, high sugar and smoking, over years, the arteries avoid the damage and
patients tend to do much better.
Two misconceptions are common about high
blood pressure ("hypertension"). First, many people think that when doctors refer to
"hypertension", that we
are talking about someone who is anxious (too much tension). While it is true that anxiety and
stress can raise blood pressure and cause hypertension, the term
"hypertension" doesn't refer to someone who is tense. People who are perfectly
calm can still have hypertension.
Second, many people think that they can "feel
their blood pressure" but in most cases, high blood pressure is a "silent
killer". Specifically, people
may have headaches that they think is caused by their blood pressure and say
that they can feel when their blood pressure is up. Basically the anxious feelings or pain due to the tension headache
(often due to contraction of the muscles of the scalp) may cause the high blood
pressure. So the high blood pressure and stress or pain may be associated but
usually the blood pressure does not cause the headache (unless a blood vessel
has ruptured which is usually severe and fairly dramatic and not the run of the
mill headache).
Most high blood pressure is what we call "essential
hypertension" which means that we really don't know what causes it. Despite years and years of research
there is still significant argument about why some people get high blood
pressure and others do not.
We know that the kidneys are involved and that salt and water are
important. Some people can control
her blood pressure and keep it down simply by avoiding salt but which we mean
table salt also known as sodium chloride.
We use drugs that cause the excretion of salt and water
("diuretics") in many patients to lower the salt and water and lower
blood pressure in patients. Losing
excess weight can also help get rid of salt and water in some patients without
drugs.
Also, the brain and nervous system are
important in blood pressure control and, as noted above, with anxiety and
stress, the body puts out more of a hormone called adrenaline which makes the
heart pump harder and blood
pressure goes up. With exercise
the heart rate and blood pressure both go up to meet the increased needs of the
body during exercise. Many of the
drugs we use to control high blood pressure work on the brain or nervous system
including such drugs as "beta blockers" or "ACE inhibitors". Also, we know that relaxation
techniques such as meditation or yoga can help to lower blood pressure in some
people presumably by effects on the brain and nervous system.
First, I must state my belief that the best way to measure blood
pressure is to do-it-yourself on a regular basis. Many people simply rely on blood pressures done in the
doctor's office or in the hospital.
However, most people know that some people have what is called
"white coat hypertension" which refers to high blood pressure in the
doctor's office. This is because
they are stressed or trying to remember things that they have heard or need to
say. Also, in many settings,
patient's blood pressures are not done sitting for 5-10 minutes.
Blood pressure can vary quite a bit from minute to minute and day to
day. When people are moving, their
blood pressure goes up. Therefore,
it is important to be sitting for at least 5-10 minutes before doing the blood
pressure if the goal is to assess whether the blood pressure is under good control. Our standards for blood pressure
control and largely related to sitting blood pressures (not lying down or
standing) and because of the known effect of moving, most studies on blood
pressures to set up normals or see about drug effectiveness are done after the
patient has been sitting for 5-10 minutes.
The advantage of the patient doing their own blood pressure is that they
can have more readings to know how their blood pressure varies under certain
conditions. For example, some
patients may have much higher blood pressures at work or conversely the blood
pressure may be low 3-4 hours after medication has been taken for blood
pressure. So it is very important
to understand the variation within the day or the variation that occurs on
weekdays versus weekends to avoid overtreating or under treating blood
pressure. This simply cannot be
done in the doctor's office (although there are special devices that can be
used to monitor the blood pressure for 24 hours at a time called ambulatory
blood pressure monitors).
Besides sitting for 5-10 minutes, the other important factor in the home
measurement of blood pressure is that the cuff must be placed at heart level.
Heart level is roughly breast level and is usually correct if the bottom of the
cuff is placed 1/2 inch to an inch above the elbow and the patient is sitting
in a high back chair with the feet on the floor. One of the problems with wrist
and finger cuffs is that they may be measuring above or below heart level if
held incorrectly.
The home blood pressure cuffs measure the pulse wave as it comes down
the arm. So it should be placed on the bare arm. Most cuffs have directions on
placing the cuff so the detector portion is over the inside of the arm where
the artery is located.
My two preferred blood pressure cuffs are Omron and LifeSource. Important features are automatic
inflation by pushing one button,
memory to store up to 30 measurements and battery and an AC adapter. All monitors mentioned also are good
for irregular heart beats which can cause problems with other monitors. All these monitors have what is called
“artificial intelligence” that lets them inflate to the appropriate blood
pressure and detect the blood pressure even with an irregular heart rhythms.
LifeSource has a cuff they call the "Easy Cuff". This cuff is 2 inches larger than the
standard medium cuff to fit more arm sizes. Omron has a similar cuff called the "Comfit"
cuff. However, if you have a very large arm or a very thin
arm you may need a different size cuff.
Typically, insurance will not cover the cost of a blood pressure cuff and
monitor -- for reasons that I don't understand. Prices for the monitor, cuff,
adapter typically range from $30-65 with the features noted. Options include online, big box stores,
smaller stores or pharmacies. Monitors and cuffs over $70 may have features you
do not need or may be overpriced.
First, bring the data and the blood pressure cuff with you when you go
to see your doctor. The doctor can compare your readings using your cuff and
monitor to their devices. Doctors offices may have an electronic type of blood
pressure measurement device or they may use the time honored method of using a
stethoscope. With the latter technique, the stethoscope is used to hear the
sound of blood when the flood flows through the cuff as the cuff pressure is
lowered (unlike the home cuffs which use a pressure wave to sense blood
pressure). Reviewing your blood
pressure technique and comparing values to those obtained by stethoscope can
add confidence that the pressure is being measured correctly. The pressure is
usually about the same in both arms unless there are blockages or problems with
the blood vessels.
As noted, "normal" blood pressure is 120/80 on average. But
some people - particularly healthy women - run lower blood pressures such as
90/50. Much below 90 for the top number (systolic) can lead to too low a
pressure ("hypotension") and problems with blood flow to vital
organs. So generally, I usually try to keep patient's systolic blood pressure
above 90 to avoid lack of flow to the brain causing passing out or
lightheadedness.
For most people, optimal blood pressure should be less than 120/80
mmHg. Although there have been
varying definitions over the years, most people would define hypertension to be
present at a pressure of greater than 130/85 consistently. Most strategies for treatment of high
blood pressure emphasize lifestyle changes initially such as lower salt, weight
loss etc. The threshold at which
blood pressure should be treated with medication varies for each patient.
Similarly, if drug treatment is needed, the choice of drug must be
individualized to the patient.
Copyright 2016 James A Heinsimer MD
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