This article will discuss blood pressure in the following sections:
- The definition of blood pressure
- How the heart pumps blood
- Blood pressure range
- High blood pressure
- Low blood pressure
- Blood pressure fluctuation
- Measuring blood pressure
- Maintaining normal blood pressure
- Blood pressure medication treatments
In today’s fast-paced society, we are continually confronted with the issue of high blood pressure. According to the Center for Disease Control (CDC), 1 out of every 3 adults has high blood pressure, putting people at greater risk for heart disease and stroke, which are leading causes of death in the United States. It is therefore of utmost importance to understand the role blood pressure plays in one’s health and be aware of what numbers fall within the normal blood pressure range. We will also give helpful tips on how to maintain a healthy blood pressure, so that readers can lower their chances of developing life-threatening illnesses.
Blood pressure is simply defined as the pressure blood exerts on the walls of blood vessels. This is usually referred to as the flow of blood in the arteries, also known as arterial blood pressure, and it depends on the following factors:
- Heart pumping activity, resulting in the resistance of blood flow in the arterioles
- The elasticity of the walls of the main arteries
- The blood volume and fluid volume
- And the blood’s thickness or density
The pumping action of the heart refers to:
- How hard the heart pumps the blood (force of heartbeat)
- How much blood it pumps (the cardiac output)
- How efficiently it does the job
- The heart’s contraction; this forces blood through the arteries, a phase known as systole (relaxation of the heart between contractions is called diastolic)
The main arteries leading from the heart have walls with strong elastic fibers; they are thus efficient at expanding and absorbing the heart’s pulsations. At each pulsation, the arteries expand and absorb in reaction to the rise in blood pressure. When the heart relaxes in preparation for another beat, the aortic valves close to prevent blood from flowing back to the heart chambers, and the artery walls bounce back, forcing the blood through the body between contractions. In this way the arteries act as dampers on the pulsations, thus developing a steady flow of blood through the blood vessels. Because of this, there are actually two blood pressures within the blood vessels during one complete beat of the heart: a higher blood pressure during systole (also known as the contraction phase) and a lower blood pressure during diastole ( known as the relaxation phase). These two blood pressures are known as systolic and diastolic blood pressure.
Below is the current medical consensus on blood pressure ranges:
- It is generally agreed that 120 mm Hg systolic and 80 mm Hg diastolic is the normal range for a blood pressure reading. It represents the average blood pressure range experienced by healthy adults. A blood pressure of 95 mm Hg systolic and 60 mm Hg diastolic may mean hypotension. A reading equal to or below this level must however be interpreted in light of each patient’s “normal” reading as determined by their baseline data.
- It is agreed that some degree of risk for cardiovascular disease exists when the systolic pressure is greater than or equal to 140 mm Hg, and the diastolic pressure is greater than or equal to 90 mm Hg. Life expectancy is reduced at all ages and in both males and females when the diastolic pressure is above 90 mm Hg.
What you need to know about high blood pressure:
- Prolonged arterial pressure puts stress on the walls and, over time, you get a heart work overload and the development of unhealthy tissue growth (also known as atheroma) within the arterial walls. The higher the pressure, the more progression of atheroma, and the more the heart muscle thickens, enlarges, and becomes weaker.
- Consistent hypertension is one of the risk factors for strokes, heart attacks, and heart failure (arterial aneurysm) and is also the leading cause of chronic kidney failure. Even moderate elevation of arterial pressure leads to shortened life expectancy. At severely high pressures (mean arterial pressures 50 percent or more above average) a person can expect to live no more than a few years unless appropriately treated.
- Most medical attention was previously paid to diastolic pressure, and not so much to systolic pressure. Today however, high diastolic and pulse pressure ( between systolic and diastolic) are also issues constantly in the limelight. In some cases, it appears that a decrease in excessive diastolic pressure can actually increase risk, probably due to the increased difference between the systolic and diastolic pressures. When systolic blood pressure is elevated, i.e. greater than 140 mmHg, together with normal diastolic blood pressure, i.e. lower than 90 mmHg, it is referred to as isolated systolic hypertension, and it may present a health concern.
- For those with heart valve regurgitation, a change in its severity may be associated with a change in diastolic pressure. During a study of people with heart valve regurgitation, comparing measurements 2 weeks apart for each person, there was an increased severity of aortic and mitral regurgitation when diastolic blood pressure increased, whereas when diastolic blood pressure decreased, there was a decreased danger.
What you need to know about low blood pressure:
- Blood pressure that is too low is known as hypotension, a medical concern with symptoms like dizziness, fainting, or in extreme cases, shock.
- When arterial pressure and blood flow decrease to a certain point, the perfusion of the brain becomes seriously decreased, meaning there is not sufficient blood flow to the brain, which can cause a lightheaded feeling, dizziness, weakness and/or fainting.
- Blood pressure can occasionally drop significantly when a person stands up from a sitting position. This is known as orthostatic hypotension (postural hypotension), when gravity reduces the rate of blood return from the lower body back to the heart, reducing stroke volume and cardiac output.
- In healthy people, the veins below the heart quickly constrict, and the heart rate increases to minimize and compensate for the gravity effect. This is carried out involuntarily by the autonomic nervous system. The system usually requires a few seconds to fully adjust, and if the compensations are too slow or not good enough, the individual will suffer reduced blood flow to the brain, dizziness and/or a potential blackout.
Different causes of low blood pressure include:
- Eating disorders, like anorexia nervosa and bulimia
- Toxins including too many blood pressure meds
- Hormonal abnormalities
- Shock is a complex condition which leads to critically decreased perfusion. The normal mechanisms are loss of blood volume, and pooling of blood within the veins which reduces the adequate return of blood to the heart and/or low effective heart pumping. Low arterial pressure, especially low pulse pressure, is a sign of shock and contributes to and reflects decreased perfusion.
- If there is a significant difference in the pressure from one arm to the other, that may indicate a narrowing (like aortic coarctation, aortic dissection, thrombosis or embolism) of an artery.
Normal fluctuation in blood pressure is adaptive and a necessity. Fluctuations in pressure that are significantly greater than the norm are associated with hyperintensity, with reduced local cerebral blood flow and a heightened risk of cerebrovascular disease. With both the lows and highs of blood pressure groups, a greater degree of fluctuation was found to relate to an increase in cerebrovascular disease compared to those with less variety. This suggests considering a clinical treatment of blood pressure changes, even among older adults with a normal blood pressure reading. Older individuals, and those who had received blood pressure medications, were more likely to exhibit larger fluctuations in pressure.
Blood pressure is usually measured in the artery of the upper arm, with a sphygmomanometer.
- This consists of a rubber cuff and a gauge or column of mercury for measuring pressure. The rubber cuff is wrapped around the person’s arm, and then air is pumped into the cuff by way of an inflation bulb. As the pressure inside the rubber cuff increases, the flow of blood through the brachial artery is quickly read.
- A stethoscope is placed over the artery at the elbow, and air pressure within the cuff is slowly released. As soon as blood begins to flow through the artery again, “Korotkoff” (after the Russian physician, Dr. Nicolai Korotkoff) sounds are heard. The first sounds heard are tapping or whooshing sounds that gradually increase in intensity. The initial tapping and whooshing sound that is heard for at least two consecutive beats is recorded as the systolic blood pressure.
- The first phase of the sounds may be followed by a momentary disappearance of sounds that can last from 30 to 40 mm Hg as the gauge needle (or mercury column) lowers. It is important that this auscultatory gap be monitored to avoid either an inaccurately low systolic pressure or high diastolic pressure.
- During the second phase subsequent to the temporary absence of sound, there are murmuring or swishing sounds. As deflation of the cuff continues, the sounds become more powerful, presenting the third phase. In phase four, the sounds become muffled quickly and are followed by silence, which is phase five.
- Although it has been argued as to which of the later phases should represent the diastolic pressure, it is usually recommended that phase five, the point that at which sounds start to disappear, be used as the diastolic pressure for adults, and phase four be used for children. The reason is that children, with a high cardiac output, will often continue to produce sounds when the gauge is at a very low reading or at zero. In some adult patients whose arterioles have lost their elasticity, the fifth phase is also extremely low or nonexistent. In these cases, it is highly suggested that three readings be recorded: phase one and phases four and five. Blood pressure would thus be written for example as 140/96/0. More often than not however, blood pressure is written as a fraction. The systolic pressure is written as the top number, a line is made, and the bottom number is diastolic.
- Flaws found in measuring blood pressure can result from failure of the cuff to reach and compress the artery. The cuff diameter should be 20 per cent greater than the diameter of the limb, and the bladder of the cuff should be centered on top of the artery, with the cuff wrapped smoothly and tightly enough to ensure proper inflation. When a mercury gauge is used, the meniscus should be at eye level to avoid a false reading.
- There is a general rule that one should use to measure blood pressure: for adults BP=100+age, and for children BP=2 x age+80
High blood pressure should be addressed first by making healthy lifestyle changes, such as:
- Limiting alcohol intake
- Quitting smoking
- Following a diet approved by the American Heart Association, or talking to your dietitian about diets low in sodium, including the DASH diet
- Increasing the level of physical exercise
- Weight loss in overweight patients is also recommended
- Medications are commonly also added to lifestyle instructions:
Antihypertensive medications are used according to evidence-based guidelines, with possible side effects:
- Diuretics, for example, are especially helpful with African Americans and older adults (but may negatively affect people with gout)
- Beta blockers are the drugs of choice in people with a history of heart problems (but there would be problems in people with a serious heart block)
- Alpha blockers work well for men with prostatic hypertrophy
- Angiotensin– converting enzyme inhibitors prevent kidney disease in persons with diabetes mellitus
- Anti-hypertensive drug classes include the angiotensin II receptor antagonists
- Calcium channel blockers: low blood pressure is not treated in healthy people or people with acute illnesses because it is often corrected with hydration or pressor agents
Below is a more in-depth description of blood pressure medications. There are quite a few medications, with a variety of risks, that help lower blood pressure if you are hypertensive:
These help the body get rid of excess salt and water, and they are often used with added prescription treatment. There are generic drugs (Hydrochlorothiazide), or brand names (Hygroton, Diuril). Potassium-sparing diuretics (triamterene), low potassium combo diuretics (Moduretic) with possible gout attacks (people with diabetes may also see an increase in blood sugar levels).
These lower the heart rate, the heart’s workload, and its output of blood, thus helping lower blood pressure. Common brand names include Sectral and Tenormin, and generic names include acebutolol and metoprolol tartrate; you should however be closely monitored if you have diabetes. Side effects may include symptoms of asthma attacks, impotence, insomnia, and a slowed heartbeat.
ACE inhibitors are chemicals that narrows the arteries in the kidneys as well as throughout the body. ACE is an acronym for Angiotensin-Converting Enzyme. ACE inhibitors help the body produce less angiotensin, which helps blood vessels relax and open up which, in turn, lowers blood pressure. There are generic brands like benazepril hydrochloride, lisinopril, and others, and common brands like Zestril, Monopril, and others. If you are considering these drugs be advised of their side effects which can include loss of taste, dry cough, skin rash and, in very minimal cases, kidney damage.
Angiotensin II Receptor Blockers
This type of medication blocks the effects of angiotensin that cause the arteries to narrow. Angiotensin needs a chemical to bind with in order to constrict the blood vessels. ARBs block the receptors so that angiotensin does not restrict the blood vessels, thus helping to lower blood pressure. Some generic name drugs include candesartan, losartan potassium, and more, and common brands include Teveten and Diovan.
Calcium Channel Blockers
Calcium channel blockers are drugs used to help relax the muscles of your blood vessels. Some slow your heart rate as well. Calcium channel blockers may work better for African Americans and older people than ACE inhibitors do alone. Common drugs include amlodipine, Cardizem, Plendil and others. Some common side effects include heart palpitations, dizziness, headache and constipation.
Central Agonists are drugs that reduce the blood vessels’ ability to tighten. They follow a different pathway than alpha and beta-blockers but achieve the same goal. Commonly used meds include alpha methyldopa, clonidine, Aldomet and Tenex. Grapefruit juice may negatively interact with some calcium channel blockers, increasing blood levels of the medication and putting you at higher risk of side effects. it is therefore advised to talk to your doctor or pharmacist if you’re concerned about these interactions.
Renin inhibitors (Aliskiren) slow down the production of renin, an enzyme produced by kidneys that starts a chain of chemical steps that increases blood pressure. Renin inhibitors work by reducing the ability of renin to begin this process. Since there is a risk of serious complications, including stroke, you shouldn’t take aliskiren with ACE inhibitors or ARBs.
In addition to reducing nerve impulses to blood vessels, alpha-beta blockers slow the heartbeat to reduce the amount of blood that needs to be pumped through the vessels. Alpha-beta blockers include generic brands like carvedilol and labetalol hydrochloride, and brand names drugs Trandate and Coreg. These can potentially cause a drop in blood pressure when standing.
Common generic and brand medications are Inspra, aldactone, spironolactone and Eplerenone. These drugs block the effects of natural chemicals that can lead to salt and fluid retention, which cause high blood pressure.
Having examined the workings of the heart, normal blood pressure, the various consequences of blood pressure fluctuations, and blood pressure medications, what should be retained, above all, are the many risks involved with medication interactions and side effects. Whatever else you do, make sure to consult your physician at every level of treatment and keep him or her informed of any side effects you are experiencing.
With healthy lifestyle adaptations and the guidance of a healthcare professional, it is possible to reclaim your health and reduce your chances of developing blood pressure irregularities that can lead to chronic disease or worse.