Diagnostic Tests

Measurement of Blood Pressure?

The measuement of blood pressure is simple, quick and virtually painless. A properly sized cuff placed around the arm is filled with enough air to squeeze the artery. This temporarily stops the flow of blood. As the air is slowly released, the doctor or nurse listens with a stethoscope as the blood starts to rush through the artery.

The first tapping sound heard is the systolic blood pressure. The systolic blood pressure is the maximum pressure produced when the heart beats and pumps blood into the arteries. The pressure is expressed as millimetres of mercury or in symbols “mm Hg”. A normal systolic blood pressure usually ranges between 100 and 140 mm Hg. A systolic blood pressure between 140 and 159 mm Hg is borderline. If the systolic blood pressure is 160 mm Hg or greater, it is called “elevated”.

The second measure used for diagnosis is the diastolic blood pressure. As more air is released from the cuff, a point is reached where the artery is fully open. At this point, the blood flows smoothly and the tapping sound over the artery disappears. The pressure, when this last sound disappears, is called diastolic blood pressure. The diastolic blood pressure represents the pressure in the arteries between heartbeats. The diastolic blood pressure normally ranges between 60 and 90 mm Hg. A diastolic blood pressure consistently at 90 mm Hg or greater is considered elevated.

For convenience, these two readings are written down together. For example, “130/80” indicates a blood pressure of 130 mm Hg systolic and 80 mm Hg diastolic.

Blood pressures taken when you are lying, sitting or standing are usually very similar. However, some people, particularly the elderly and diabetics, may have much lower pressures when they stand up. Also, some drugs lower standing blood pressure more than lying blood pressure. In these situations, the pressure is often measured both while lying and standing. Many doctors feels that the most useful blood pressure measurement is one taken while sitting quietly, without talking, because it represents the usual way most of us spend our daytime hours.

No matter which position one is in, one must be comfortable and have the arm supported. If the arm is unsupported, the arm muscles have to work, and this raises the blood pressure readings. Support can be given by the doctor’s or nurse’s hand or by resting your arm on a table or the arm of a chair. Also, it is not uncommon to find up to a 5 mm Hg difference between the two arms. The custom is to use the arm with the higher blood pressure for all subsequent visits.

Role of Home Blood Pressure Measurement

Certain people have consistently lower blood pressure at home than at their doctor’s office. Some people also find it helpful to see the effect of their medications on their blood pressure. In addition, some doctors believe it is easier to adjust medications and to help people follow their treatments if blood pressures are taken between visits as well as at the clinic. If one is interested in purchasing a blood pressure kit for one’s use it can be done with a medical practitioner’s advice. However, one must be aware that the diagnosis of high blood pressure is based on the office blood pressure. At present, the role of home or self-monitored blood pressure remains unclear, and further research is needed.

All people doing self-monitoring should have proper training in the method, and need to have their machines checked periodically for accuracy. It helps to have a physician or nurse available to contact. In some patients self-monitoring of blood pressure may result in excess concern about the usual peaks of blood pressure, and may increase anxieties about health. It is important to understand that blood pressure varies with time in everyone. This means the blood pressure could be 156/92 mm Hg at one time and 132/86 just a few minutes later. This variability is normal. The level of blood pressure used to decide about treatment is based on the average of several readings, not any single reading.

One may be able to obtain additional readings in other ways, too. If a nurse visits one’s home regularly or if one can see a nurse at a place of work, one can have him/her check the blood pressure and write down the readings with the date and time so that these readings can be shown to the doctor. However, usage of machines available in public places is not recommended as most of the times it is inaccurate.

Ambulatory Blood Pressure Monitoring

Portable automatic blood pressure measuring devices are now available through some doctor’s offices. These can record blood pressure many times throughout the day. A typical blood pressure cuff is worn and a small pump inflates and deflates the cuff automatically. These machines are no larger than a paperback and are worn on the belt or a shoulder strap. They are reasonably comfortable to wear and don’t usually disrupt the daily routine or sleep. Information is stored in the unit’s memory and later transferred to a computer for printout. With these machines an average blood pressure can be determined during many different activities. Of interest, average ambulatory blood pressure during the day is about 5 mm Hg lower than the office blood pressure.

Ambulatory blood pressure monitoring is still mainly a research tool. It may be useful in patients who have only borderline pressure elevation or if white coat syndrome is suspected. In this condition, blood pressure is elevated in the physician’s office but is lower elsewhere or even normal. However, only further research will clarify Whether a patient with hypertension in the office can go without treatment but a normal ambulatory blood pressure can safely go without treatment. For now, both ambulatory blood pressure and home blood pressure are best viewed as providing special pieces of information that are sometimes used in deciding whether an elevated office blood pressure requires treatment or not.

Diagnosis of High Blood Pressure

Does one elevated blood pressure reading means that you have “high blood pressure”? No! As we mentioned, blood pressure varies continuously. There are many reasons for pressures to be high at any one time. Pressures taken just after exercise or when you are upset may be higher as a temporary response to the situation. A blood pressure that remains high after five minutes of sitting quietly is more important. Even then, just the situation of having one’s blood pressure taken can elevate the reading. To overcome this, your physician may measure your blood pressure twice or more during a visit and record only the lowest pressure.

Medical authorities agree that a minimum of two elevated blood pressure readings taken on at least two or three different days are needed to make the diagnosis of high blood pressure or hypertension. Furthermore, research shows that blood pressure taken in the doctor’s office may continue to drop for up to six months. Due to this the recommendation is that, for people whose diastolic blood pressure appears only mildly elevated, the diagnosis of “high blood pressure” should be based on at least three blood pressure measurements over a period of six months.

This period may be shortened if the blood pressure is moderately elevated or if there is any evidence of damage from the high blood pressure.

Unfortunately, there are many people who believe they have high blood pressure because they have had one elevated blood pressure reading, even though readings after that time have been normal. In fact, a recent survey showed that there were more people with normal readings though they had high blood pressure than there were people who actually had high blood pressure. If one is not on antihypertensive medication and the blood pressure at doctor’s office is usually normal (less than 140/ 90 mm Hg) then one does not have hypertension.

Importance of Systolic Blood Pressure

A systolic blood pressure of repeatedly 160 mm Hg or greater with a diastolic blood pressure below 90 mm Hg is called Isolated Systolic Hypertension. Elevated systolic pressure with or without elevated diastolic pressure occurs mostly in the elderly. Treating elevated systolic pressure has recently been proved to decrease the risk of heart disease and stroke, at least for persons aged 60 and older. This is an important new finding.

Doctor’s Investigation of High Blood Pressure

Once the doctor has made certain that you really have high blood pressure, he/she will investigate further.

  1. An interview about your medical history, current health and related activities.
  2. A physical examination.
  3. Routine tests.
  4. Other tests may be done.

Each time the doctor does one of the above steps shown in table 6.1 he/ she is trying to find the answer to at least one of the following three questions:

  1. What is the cause of the high blood pressure?
  2. Has the high blood pressure had anylasting effect on your body?
  3. Are there any other factors that may increase your chance of having a stroke, heart problems or other complications of high blood pressure?

Finding a cause for the high blood pressure may allow partial or complete cure. If the elevated blood pressure has affected your body or you have other factors that increase the risk of a complication, it may be important to start treatment at lower level of elevated blood pressure. Also, if one does have other untreated risk factors, these will need to be attended to.

Causes of High Blood Pressure

In about 95 of 100 cases no clear cause of high blood pressure can be found even after a thorough investigation. This is called Primary or Essential Hypertension. In only about one to two of 100 cases is a treatable cause found; it cannot be cured although blood pressure can almost always be controlled.

The most easily treated causes of elevated blood pressure can all be discovered by simple questions:

1) Are you taking Any Medications?

Some drugs, both prescription and non-prescription, increase blood pressure. By stopping them, the blood pressure often returns to normal. The most commonly used drugs that can elevate blood pressure are birth control pills and other ‘hormone pills’ that contain estrogen. Cold or sinus remedies or allergy tablet that contain decongestant can contract the blood vessel and can occasionally raise the blood pressure. A similar effect is seen with some diet pills and herbal remedies, Non-steroidal anti­inflammatory drugs (NSAIDS), such as ibuprofen commonly used to relieve urethritis, can also raise blood pressure.

2) Licorice, alcohol or salt intake? Any change in your weight?

Things that one eats and drinks can easily affect one’s blood pressure. Only very rarely does a person eat licorice every day, but that can easily be remedied. The more alcohol one drinks (above two drinks per day), the higher the blood pressure. This rise in pressure is quickly reversed by cutting back on alcohol. Some people’s blood pressure is “salt sensitive”. High blood pressure is also related to being overweight.

3) Have you been under stress recently?

A stressful situation such as a problem at work, a financial crisis, or family troubles can raise your blood pressure temporarily. If the doctor finds that you are under stress, he may choose to have the person come back at a less stressful time to check your blood pressure.

We must note here that many people think that high blood pressure is a ‘stress’ disease and that every person who is anxious or under stress has high blood pressure. This is seldom the case. People who feel stressed may have high blood pressure but this is not often due to the stress itself. On the other hand, people who feel relaxed still have high blood pressure. The only way to tell is to measure the blood pressure.

4) Have you had any problems with your kidneys?

The kidney play an important role in controlling your blood pressure. Since kidney problems may lead to high blood pressure the doctor may will look far.

Chronic Renal Disease: Chronic kidney disease stands as the most frequent cause of high blood pressure. The doctor will enquire about chronic kidney and urinary infections, kidney injury from accidents or kidney stones. He will examine your urine for protein and cells that should not be there. He will also take blood tests for creatinine or urea as indicators of how well the kidneys are working

Narrowing of the Artery to the Kidneys (“Renal Artery Stenosis”): If the blood supply to a kidney is reduced because of a partial blockage, the kidney will respond by demanding a higher blood pressure. Blood flowing through the narrowed artery can make a noise that can be heard through the doctor’s stethoscope. If he hears this noise when listening over your abdomen, he may then order a renal scan, a test which involves the injection of a small and safe amount of radioactive dye, and then lying beneath a scanner that sees the dye as it is taken up by the kidneys. Another similar test is the Intravenous Pyelogram or IVP. This involves the injection of a small amount of dye or contrast that shows up on an x-ray when the dye enters the kidneys.

If a blocked artery to the kidney it still suspected after the initial tests, then an x-ray picture can be taken of the artery to the kidney. This x-ray is called an Arteriogram or Angiogram. A small tube is inserted through an artery in the groin and moved inside the artery until it is near the kidney. X-ray dye is then injected. As the dye flows through the artery to the kidney an x­ray movie will reveal any blockage or narrowing.

As final proof that the kidney with a narrowed artery is causing the high blood pressure, a renal vein renin test may be performed. Renin is a hormone produced by the kidney to raise blood pressure. If one kidney is causing the high blood pressure, it may over-produce renin. This is measured through a small tube inserted into the groin vein to reach the vein leaving each kidney.

Do you have any problems with your adrenal glands? The adrenals are small glands that secrete hormones from their location atop each kidney. An overactive adrenal gland can produce an excess of the hormone aldosterone, which raises the blood pressure. Low potassium in the blood is a clue.

Adrenal Hyperactivity (Cushings Syndrome)

If the adrenal glands produce too much of the hormone Cortisone, the blood pressure will be raised. The clue to this disease is unusual weight gain on the upper back and abdomen. Distinctive violet­coloured stretch marks may develop on the abdomen. Blood or urine testing will reveal excess cortisone.

Pheochromocytoma

The cause of high blood pressure here is a tumour of the central part of the adrenal gland, the adrenal medulla. The clues come from the medical history. Persons with this problem complain of attacks of headache, sweating, tremor and heart palpitations. If you report these symptoms the doctor will ask you to collect the urine for 24 hours. This is then analysed for chemicals secreted by the tumour. If this test is positive, then special x-rays are done to locate the tumour, which can often be removed by surgery.

Effect of Blood Pressure on Body

If the blood pressure is very high or high for a long time, it can affect several bodily organs. If the doctor finds such effects of high blood pressure, this is important knowledge when deciding about treatment.

When the heart works against higher pressure it becomes larger. Enlargement leads to changes in the Electro Cardiogram (ECG or EKG) and the echo cardiogram (ultrasound of the heart).A chest x-ray is a less sensitive way to show increase in heart size. If the heart muscle is overworked for a very long time, fluid may back up into the lungs. This is called Congestive Heart Failure. The fluid is easily heard over the lungs with a stethoscope and can be seen in the chest x-ray.

A second area of the body to be affected is the kidney. Prolonged high blood pressure can wear out the kidneys. This can be detected by a simple blood test. A 24-hour urine collection is often added for more information.

High blood pressure can also affect the blood vessels. By looking into the eye with an ophthalmoscope, the doctor can see what is happening to the blood vessels in the body. With severe hypertension, the blood vessels become narrowed and twisted. The vessels can also leak fluid or blood that can be seen as white or red patches on the back of the eye. The doctor will also examine the larger blood vessels of the body for narrowing or enlargement due to high blood pressure.

Since high blood pressure is treated primarily to lower our chance of having a stroke or heart trouble, the doctor must know about anything else that could increase your chance of having either of these problems. If your chances of a stroke or heart trouble are higher, if members of close family had either of these, if one smokes, or if one has diabetes or increased cholesterol, the doctor will check these as well.

Spring Gauge Models

Health care professionals often recommend spring-gauge models because they’re inexpensive and easy to transport. In addition, some gauges are extra large, for easier reading, and some models have a built-in stethoscope for easier use.

A disadvantage is that once a year you need to verify the monitor’s accuracy by comparing it with a mercury-column model. You can do this by taking your monitor with you to your doctor’s office. If the reading is more than 4 millimetres off, you should replace the unit.

Like mercury-column models, standard spring-gauge monitors aren’t recommended if you have trouble hearing or if you have poor dexterity in your hands. They also require use of stethoscope and bulb pump.

Electronic Models

Also refered to as digital monitors, these models are the most popular and easiest to use. They are also the most expensive. Prices can run as high as $160, compared with as little as $30 for a standard spring-gauge model.

Electronic blood pressure monitors generally require that you do just two things: Put the cuff on your arm and push a button. The cuff automatically inflates with air and then slowly deflates. Built in sensors detect your blood pressure and display the measurement on a screen.

To get an accurate reading, place the sensor over the main artery (brachial) in your arm. It is also important that the cuff fits you properly and you have the appropriate size cuff.

Like spring-gauge models, you need to check the monitor’s accuracy at least once a year. Electronic monitors are less accurate than the previous types and the easiest to damage.

If you have an irregular heart rhythm, you shouldn’t use an electronic monitor because it will give you an inaccurate reading.

Finger or Wrist Monitors

To make blood pressure monitors more compact and easier to use, some manufacturers have produced models that easily measure blood presure in your wrist or finger, instead of your upper arm.